WO2023044533A1

WO2023044533A1 - Production of clean hydrogen

Info

Publication number: WO2023044533A1
Application number: PCT/AU2022/051139
Authority: WO
Inventors: Hongjun CHEN; Anita HO-BAILLIE
Original assignee: The University Of Sydney
Priority date: 2021-09-21
Filing date: 2022-09-21
Publication date: 2023-03-30

Abstract

The present invention relates to the photovoltaic production of hydrogen gas and conductive polymers, particularly an electrolytic cell, comprising: an electrolyte solution, comprising water, an acid and a monomer for producing a conductive polymer; an anode and a cathode in fluid contact with the electrolyte; and an electricity source, which is in electrical contact with the anode and the cathode, wherein the electricity source converts light from a light source into electricity, wherein, in use, the electricity source provides a voltage to the electrolytic cell that is sufficient to oxidize the monomer and produce hydrogen gas at the cathode. The present invention also relates to a process for the photovoltaic production of hydrogen gas and conductive polymers and products obtained therefrom.

Description

PRODUCTION OF CLEAN HYDROGEN

Field

[0001] This invention relates to the photovoltaic production of hydrogen gas and conductive polymers, as well as apparatus and processes thereof.

Background

[0002] Recently, there has been an increase in research in developing hydrogen gas, H2, as a renewable energy source that is an alternative to carbon-based fossil fuels, or as a way of storing renewable energy when produced in excess (for example, for storing solar energy for use at night, or wind energy for use during calm conditions). However, in order to truly be a renewable energy source, the H2 gas must be produced from a renewable substrate (i.e., not a fossil fuel such as natural gas) and using energy from a renewable source. The traditional approach to producing renewable H2 gas is the electrolysis of water, whereby a voltage is applied to an electrolytic cell and water is split into hydrogen gas and oxygen gas, with the hydrogen evolution reaction (HER) occurring at the cathode and the oxygen evolution reaction (OER) occurring at the anode. The redox half equations for the electrolysis of water are:

Oxidation: 2H2O — 4H⁺ + 4e“ + O2 E° = 1.23 V vs. Normal Hydrogen Electrode (NHE)

Reduction: 4H⁺ + 4e 2H₂ E° = 0.00 V vs. NHE

Overall: 2H₂O 2H₂ + O₂ E°cell = - 1.23 V

[0003] However, one of the drawbacks of the traditional approach to producing hydrogen gas by hydrolysing water is that both products, H2 and O2, are gaseous. This can add difficulty and complexity to a commercial process, as the two gasses need to be kept separate so as to produce pure products without the need for further processing and to avoid potentially explosive reactions.

[0004] Another drawback of the traditional water splitting process is the significant voltage difference required to drive the electrochemical hydrolysis. Whilst the required voltage bias to break the strong covalent bonds in water is 1.23 V in theory (as shown above), in practice a voltage difference across the cell of between about 1.6 and 1.8 V is required to overcome the activation barrier of the reaction. This significant voltage difference (or overpotential) is due to the slow four-electron transfer kinetics of the OER at the anode in comparison to the fast two- electron transfer kinetics of the HER at the cathode.

[0005] To be a renewable energy source or storage medium, the hydrogen production must be driven by a renewable energy source. Whilst a solar-driven water hydrolysis method has been under development for some time, the voltage bias of between 1.6 and 1.8 V required to hydrolyse water has been a barrier to the development of this technology. For instance, most silicon-based photovoltaic cells, which are currently the most common solar cell technology available, produce a voltage of about 0.5 V, meaning that a series of at least four solar cells are required to hydrolyse water.

[0006] Accordingly, there is a need for a process for hydrolysing water with a lower voltage bias. Preferably, the hydrolysis would occur at a voltage bias that would allow for the direct production of hydrogen by use of photovoltaic or solar cells.

Summary of Invention

[0007] The present invention aims to address at least one of the deficiencies of the current water hydrolysis process for producing hydrogen gas using solar power technologies. In particular, the present invention aims to reduce the voltage bias required to produce hydrogen gas via an electrochemical reaction by replacing the OER at the anode with an oxidation reaction that has a lower potential so as to provide a process suitable for use with a photovoltaic energy source, and/or to replace the product formed at the anode with a solid so as to provide an easier separation of products.

[0008] In one aspect of the present invention, there is provided an electrolytic cell, comprising: an electrolyte solution, comprising water, an acid and a monomer for producing a conductive polymer; an anode and a cathode in fluid contact with the electrolyte; and an electricity source, which is in electrical contact with the anode and the cathode, wherein the electricity source converts light from a light source into electricity, wherein, in use, the electricity source provides a voltage to the electrolytic cell that is sufficient to oxidize the monomer and produce hydrogen gas at the cathode. [0009] The following options may be used in conjunction with the first aspect, either individually or in any suitable combination.

[00010] The electrolyte solution comprises a monomer for producing a conductive polymer. The conductive polymer may be a homogenous polymer (i.e., formed from one monomer type) or it may be a co-polymer, such as a random co-polymer (i.e., formed from two or more monomer types present in the electrolyte solution). The monomer may be selected from the group consisting of aniline, pyrrole, thiophene, 3,4-ethylenedioxythiophene and indole, and derivatives thereof, and mixtures thereof. In this context, a “derivative” is a monomer that includes the substitution of at least one hydrogen atom, at a position that this not required for polymerization, with at least one suitable non-hydrogen group. A suitable substitution group may comprise an electron withdrawing group, or an electron donating group, or any electrically neutral, or nonpolar, group. The substituent may be halogen (e.g., F, Cl, Br or I), a cyano group (-CN), a carbonyl group, a nitro group (-NO3), an alkyl group, an alkenyl group, an alkynyl group, an alcohol group, or an amino group, and the substituent group may be optionally further substituted. The monomer may be oxidized at the anode so as to form a conductive polymer selected from the group consisting of polyaniline, polypyrrole, polythiophene, poly(3,4- ethylenedioxy thiophene), and polyindole, and derivatives thereof, and co-polymers thereof.

[00011] The electrolytic cell may comprise an acid. Any acid that completely or partially ionises in aqueous solution, and is not oxidised by the anode or reduced by the cathode, may be suitable for use in the electrolytic cell of the present invention. The acid may be a mineral acid, or it may be an organic acid, or it may be any mixture thereof. The mineral acid may be selected from the group consisting of hydrochloric acid (HC1), nitric acid (HNO3), sulphuric acid (H2SO4), phosphoric acid (H3PO4), boric acid (H3BO3), perchloric acid (HCIO4) and any mixture thereof. The organic acid may be selected from the group consisting of acetic acid (HC2H3O2), carbonic acid (H2CO3), formic acid (H2CO2), lactic acid (CH3CH(OH)COOH), citric acid (HOC(CO2H)(CH2CO2H)2), and any mixture thereof. The pH of the electrolyte solution may be less than 7 (i.e., at an acidic pH). The pH may be less than about 6, or less than about 5, or less than about 4, or it may be a pH of about 0, 1, 2, 3, 4, 5, 6, or 7.

[00012] The electrolyte solution may optionally further comprise a redox mediator capable of oxidizing the monomer. The redox mediator may be used to transfer electrons from the anode to the monomer, causing oxidation of the monomer and hence initiation of the polymerization reaction. In this regard, the anode may indirectly oxidize the monomer, via the redox mediator (when present), as opposed to directly oxidize the monomer (when the oxidation of the monomer occurs at the anode). The redox mediator of the present invention may be any suitable redox mediator known in the art. Preferably, the redox mediator must be able to both oxidize the monomer and be oxidized from its reduced form by a voltage obtainable by the electricity source. In one preferred embodiment, the redox mediator is a triiodide ion (I3 ).

[00013] The electricity source may be any suitable device for providing an electrical current to the electrolytic cell of the present invention. In a preferred embodiment, the electricity source provides electricity from a renewable energy source. The electricity source may utilize solar power. The electricity source may be a photovoltaic cell. The photovoltaic cell may be a silicon- based cell, a thin-film cell (e.g., copper indium gallium selenide (CIGS) cell, or copper zinc tin sulfide (CZTS) cell), a multi-j unction cell (e.g., a combined tandem solar cell), a perovskite cell, a III-V cell, a dye-sensitized cell, or comprises colloidal quantum dots or organic polymers. The electricity source may include a single photovoltaic cell, or it may include two or more photovoltaic cells connected in series. The electricity source may provide a voltage of between about 0.4 V and about 1.8 V, or it may be between about 0.5 V and about 1 V, or it may be between about 1 V and about 1.8, or it may be about 0.4 V, 0.45 V, 0.5 V, 0.55 V, 0.6 V, 0.65 V, 0.7 V, 0.75 V, 0.8 V, 0.85 V, 0.9 V, 0.95 V, 1 V, 1.05 V, 1.1 V, 1.15 V, 1.2 V, 1.25 V, 1.3 V, 1.35 V, 1.4 V, 1.45 V, 1.5 V, 1.55 V, 1.6 V, 1.65 V, 1.7 V, 1.75 V, or 1.8 V.

[00014] The cathode of the electrolytic cell may be made of any suitable conductive material. The cathode may comprise a metal-based material. The metal-based material may comprise a metal, a metal oxide, a metal alloy, a metal phosphide or a metal dichalcogenide, each of which comprises at least one of the metals selected from platinum, palladium, rhodium, cobalt, molybdenum, nickel and manganese. By “metal phosphide”, it is meant a material such as cobalt phosphide (CoP) or nickel phosphide (N12P). By “metal dichalcogenide”, it is meant a material such as cobalt diselenide (CoSe2) or molybdenum sulfide (M0S2). The cathode may comprise a carbon-based material such as, for example, graphite or a carbon nanotube. The cathode may comprise a semiconductor material, such as, for example, copper(I) oxide (CU2O), p-type silicon and indium phosphide (InP). The cathode may comprise any mixture of at least one metal-based material and/or at least one carbon-based material, and/or at least one semiconductor material thereof. The cathode may be any suitable size, shape and dimension suitable for the design of the overall electrolytic cell. In some embodiments, the electricity source, such as a photovoltaic cell or photoactive material (i.e., a photoanode), is in fluid contact with the electrolyte solution and acts as the anode.

[00015] The anode of the electrolytic cell may be made of any suitable conductive material. In some embodiments, the anode may comprise a conductive glass (such as fluorine-doped tin oxide), or a metal or metal alloy comprising at least one metal (such as nickel, titanium, gold, platinum or stainless steel), or a carbon-based conductive material (graphite or carbon nanotubes), or a semiconductor material (such as titanium dioxide (TiCh), zinc oxide (ZnO), tungsten trioxide (WO3), bismuth vanadate (BiVCU), iron(III) oxide / a-hematite (Fe2O3), or gallium nitride (GaN)), or any mixture thereof. In some embodiments, the electricity source, such as a photovoltaic cell or a photoactive material (i.e., a photocathode), is in fluid contact with the electrolyte solution and acts as the anode.

[00016] The electrolytic cell may further comprise a multimeter capable of monitoring the current and/or the voltage of the electrolytic cell during use. The multimeter may be in series with the electricity source. It may be in electrical contact with the working electrode, the reference electrode and the counter electrode. The working electrode may be the anode. In some embodiments, the counter electrode and the reference electrode may both be the cathode. In other embodiments, the reference electrode is a separate electrode and in fluid contact with the electrolyte solution.

[00017] The electrolytic cell may further comprise a storage device for storing energy. The storage device may be a battery for storing excess electrical charge. The storage device may be a hydrogen fuel cell that uses some of the produced hydrogen to generate an electrical current.

[00018] The electrolytic cell may further comprise a second light source that is not solar light. The second light source may be arranged so as to illuminate the electricity source when the solar light source is unavailable, or not at a sufficient intensity.

[00019] The electrolytic cell may further comprise a stirring system in fluid contact with the electrolyte solution. Any suitable stirring system may be used that is capable of maintaining the homogeneity of the electrolyte solution.

[00020] In one embodiment, the present invention provides an electrolytic cell, comprising an electrolyte solution. The electrolyte solution comprises water, sulphuric acid, and a monomer selected from the group consisting of aniline, pyrrole, thiophene, 3,4-ethylenedioxythiophene and indole. The electricity source of the embodiment is two silicon-based photovoltaic cells in series and is in electrical contact with the anode, which comprises a fluorine-doped tin oxide glass, or a nickel foam, or a titanium sheet, and the cathode, which comprises a platinum sheet, or a molybdenum-nickel alloy. When the photovoltaic cells are illuminated, the device produces a voltage of between about 1 V and 1.5 V, which is enough to produce hydrogen gas at the cathode and a conductive polymer at the anode.

[00021] In another embodiment, the present invention provides an electrolytic cell, comprising an electrolyte solution. The electrolyte solution comprises water, an acid selected from hydrochloric acid (HC1), sulphuric acid (H2SO4) and perchloric acid (HCIO4), and aniline. The electricity source of the embodiment is a photovoltaic cell selected from a perovskite cell or a III-V cell and is in electrical contact with the anode, which is selected from a fluorine-doped tin oxide glass, a nickel foam, and a titanium sheet, and the cathode, which comprises a platinum sheet, or a molybdenum-nickel alloy. When the photovoltaic cell is illuminated by solar light or a second light source, the device produces a voltage of between about 1 V and 1.5 V, which is sufficient to produce hydrogen gas at the cathode and polyaniline at the anode.

[00022] In yet another embodiment, the present invention provides an electrolytic cell, comprising an electrolyte solution. The electrolyte solution comprises water, sulphuric acid (H2SO4) at a concentration of between 0.1 M and 0.5 M, and aniline at a concentration of between 0.1 M and 0.2 M. The electricity source of the embodiment is two silicon-based photovoltaic cells in series and is in electrical contact with the anode, which is a titanium electrode, and the cathode, which is a platinum electrode. When the photovoltaic cell is illuminated by solar light or a second light source such as a halogen light bulb or at least one light emitting diode (LED), the device produces a voltage of between about 1 V and 1.5 V, which is sufficient to produce hydrogen gas at the cathode and polyaniline at the anode.

[00023] In another embodiment, the present invention provides an electrolytic cell, comprising an electrolyte solution. The electrolyte solution comprises water, a mineral acid, and a monomer capable of forming of a conductive polymer. The electricity source of the embodiment is a photovoltaic cell selected from a silicon-based cell, a perovskite cell and a III-V cell. The electricity source is in fluid contact with the electrolyte solution (and therefore acts as the anode), and in electrical contact with the cathode, which comprises a platinum sheet, or a molybdenum-nickel alloy. When the photovoltaic cell is illuminated by solar light , the device produces a voltage of between about 1 V and 1.5 V, which is sufficient to produce hydrogen gas at the cathode and a conductive polymer at the anode.

[00024] In a second aspect of the present invention, there is provided a process for simultaneous production of a conductive polymer and hydrogen gas, comprising: obtaining an electrolytic cell of the first aspect; and exposing the electricity source to a solar light source; wherein the electricity from the device initiates a polymerization reaction at the anode to produce a conductive polymer, and hydrogen gas is produced at the cathode.

Brief Description of Drawings

[00025] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying figures, wherein:

[00026] Figure 1 shows a representative diagram of the structure of an electrolytic cell capable of producing hydrogen, whereby the anode and cathode are not photosensitive and the electricity source (such as the PV cell) is outside of the reactor.

[00027] Figure 2 shows a representative diagram of another structure of an electrolytic cell capable of producing hydrogen, whereby the anode is photosensitive.

[00028] Figure 3 shows a representative diagram of another structure of an electrolytic cell capable of producing hydrogen, whereby the cathode is photosensitive.

[00029] Figure 4 displays data collected when the electrolytic cell is run with sulphuric acid (H2SO4) as the electrolyte and aniline as the monomer. The material produced at the anode was characterised by FTIR (Figure 4 A) and Raman (Figure 4B) spectroscopy; the efficiency of the cell was also investigated over a 120-min runtime, with current and charge measured (Figure 4C) as well as the measured H2 production in mmole- h^-L ¹ at each ten minute interval, and the Faradaic efficiency calculated (Figure 4D). [00030] Figure 5 shows (a) the amperometric curve and (b) UV-vis spectra at different times when the electrolytic cell is run with a simulated wastewater comprising 0.0129 M aniline and 0.5 M H2SO4.

[00031] Figure 6 shows the stability of polyaniline under a negative potential (-0.4 V vs Pt) in a 1 M H2SO4 solution, in terms of (a) cyclic voltammogram (CV) curve of polyaniline before and after 73 h of stability test and (b) the current over time for the 73 hour test.

[00032] Figure 7 shows the stability of polyaniline under a positive potential (+1.8 V vs Pt) in a 1 M H2SO4 solution, in terms of (a) cyclic voltammogram (CV) curve of polyaniline before and after 43 h of stability test and (b) the current over time for the 43 hour test.

[00033] Figure 8 shows the polymerisation of pyrrole to polypyrrole in terms of (a) cyclic voltammogram (CV) curve and (b) amperometric curve.

[00034] Figure 9 shows the polymerisation of pyrrole to polypyrrole using the redox mediator I₃ /T in terms of (a) cyclic voltammogram (CV) curve and (b) amperometric curve.

Definitions

[00035] The following definitions are provided to enable the skilled person to better understand the invention disclosed herein. These are intended to be general and are not intended to limit the scope of the invention to these terms or definitions alone.

[00036] As used herein, the term “comprising” means “including”. Variations of the word “comprising”, such as “comprise” and “comprises”, have correspondingly varied meanings. As used herein, the terms “including” and “comprising” are non-exclusive. As used herein, the terms “including” and “comprising” do not imply that the specified integer(s) represent a major part of the whole.

[00037] The transitional phrase “consisting of’ excludes any element, step, or ingredient not specified. If in the claim, such would close the claim to the inclusion of materials other than those recited except for impurities ordinarily associated therewith. When the phrase “consisting of’ appears in a clause of the body of a claim, rather than immediately following the preamble, it limits only the element set forth in that clause; other elements are not excluded from the claim as a whole.

[00038] The transitional phrase “consisting essentially of’ is used to define a composition, process or method that includes materials, steps, features, components, or elements, in addition to those literally disclosed, provided that these additional materials, steps, features, components, or elements do not materially affect the basic and novel characteristic(s) of the claimed invention. The term “consisting essentially of’ occupies a middle ground between "comprising" and “consisting of’.

[00039] Where applicants have defined an invention or a portion thereof with an open-ended term such as “comprising”, it should be readily understood that (unless otherwise stated) the description should be interpreted to also describe such an invention using the terms “consisting essentially of’ or “consisting of. ” In other words, with respect to the terms “comprising”, “consisting of’, and “consisting essentially of’, where one of these three terms are used herein, the presently disclosed and claimed subject matter may include the use of either of the other two terms. Thus, in some embodiments not otherwise explicitly recited, any instance of “comprising” may be replaced by “consisting of’ or, alternatively, by “consisting essentially of’.

[00040] Further, unless expressly stated to the contrary, “or” refers to an inclusive or and not to an exclusive or. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

[00041] Also, the indefinite articles “a” and “an” preceding an element or component of the invention are intended to be non-restrictive regarding the number of instances (i.e., occurrences) of the element or component. Therefore “a” or “an” should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular.

[00042] The terms “predominantly” and “substantially” as used herein shall mean comprising more than 50% by weight, unless otherwise indicated. [00043] As used herein, with reference to numbers in a range of numerals, the terms “about” or “approximately” are understood to refer to the range of -10% to +10% of the referenced number, preferably -5% to +5% of the referenced number, more preferably -1 % to + 1 % of the referenced number, most preferably -0.1 % to +0.1 % of the referenced number. Moreover, with reference to numerical ranges, these terms should be construed as providing support for a claim directed to any number or subset of numbers in that range. For example, a disclosure of from 1 to 10 should be construed as supporting a range of from 1 to 8, from 3 to 7, from 1 to 9, from 3.6 to 4.6, from 3.5 to 9.9, from 8 to 10, and so forth.

Description of Embodiments

[00044] The following description conveys exemplary embodiments of the present invention in sufficient detail to enable those of ordinary skill in the art to practice the present invention. Features or limitations of the various embodiments described do not necessarily limit other embodiments of the present invention or the present invention as a whole. Hence, the following detailed description does not limit the scope of the present invention, which is defined only by the claims.

[00045] The present invention relates to a process and an apparatus for producing hydrogen gas using a renewable energy source. In order to use a renewable energy source to produce hydrogen, a more energy-efficient process is needed whereby the voltage bias of the electrolytic cell is reduced. The inventors of the present invention have achieved this voltage reduction by replacing the energetically costly OER at the cathode in traditional water-splitting processes with a process with a lower required E° voltage.

[00046] The present invention replaces the OER at the anode with an oxidative polymerisation reaction. By doing so, the overall voltage bias required by an electrolytic cell to produce hydrogen gas can be significantly reduced, resulting in a more efficient process.

Advantageously, oxidative polymerisation reactions can be selected that reduces the voltage gap so as to allow supply of electricity to the electrolytic cell by a solar energy device, such as a photovoltaic cell. Additionally, the polymer that is produced at the anode is a solid, meaning that expensive membranes or complex cell design is not required in order to keep the products separate. A further advantage of this invention is that the polymer produced at the anode will generally have a higher resale value compared to oxygen gas, meaning that an economic advantage is obtained. As will be described in greater detail below and with reference to the examples, an electrolytic cell that produces a conductive polymer at the anode and hydrogen gas at the cathode, powered by renewable energy (such as solar power generating electricity via a photovoltaic cell), provides advantages over the currently known hydrogen production techniques.

Polymer

[00047] It is commonly known that polymers are formed from the polymerisation of monomers, whereby the monomers react and become covalently bound together. There are two basic types of polymerisation reactions, generally referred to as addition (or chain -reaction) and condensation (or step -reaction) polymerisation. Essentially, in addition polymerisation, unsaturated monomers (i.e., organic compounds with at least one double bond or triple bond) react to form a new covalent bond, whereby the electrons forming the new covalent bond are donated by the unsaturated bond of the monomer. In a condensation polymerisation reaction, two monomers react together, resulting in the loss of a water molecule per new bond. Generally, the monomers in an addition polymerisation reaction maintain their identity in the polymer chain (e.g., A + A + A — A-A-A), whereas the monomers in a condensation polymerisation reaction form a polymer with a new repeating unit (e.g., A + B + A + B ^ C-C).

[00048] In order to initiate and propagate an addition polymerisation reaction, it is necessary to oxidise at least some of the monomers so that they are reactive with other monomers. Oxidation can be initiated by any suitable oxidising process, such as a chemical process, or an electrochemical process. One approach is to use free -radical polymerisation, whereby a polymer chain starts with a monomer that has become a free radical, either through a chemical reaction with a stable radical chemical species under mild conditions and the polymerisation propagates with the addition of further monomers, ending when another free radical monomer is added. Free-radical polymerisation is usually initiated by a catalyst, such as a free radical initiator (which may itself be a stable free radical, such as, for example, di-/c/7-butyl peroxide, benzoyl peroxide, 2,2'-azobis(2-methylpropionitrile) and the like), an acid, a carbanion or a metal complex. However, monomers can also be oxidised at the anode in an electrolytic cell, whereby an electron is stripped from the monomer or a terminal unit of a polymer chain to form a reactive free radical site for the addition of further monomers. In other words, in order to electrochemically initiate and propagate an additive polymerisation reaction, the anode must be in electrical contact with a monomer.

[00049] Whilst many different types of polymers are known, one subset of polymers are known as “conductive polymers”. It is understood that a “conductive polymer” (or interchangeably a “conducting polymer”) refers to an organic polymer that conducts electricity. They may also be known as “intrinsically conductive polymers”, to differentiate the polymers that are capable of conducting electricity without the addition of further substituents or dopants, from those polymers that may be capable of conducting electricity only after doping with electron-rich or electron-poor groups that are not present in the parent monomers. Conductive polymers gain their electrical properties from a highly conjugated backbone that includes a continual chain of sp² hybridized carbon centres. It is understood that, with a continuous backbone of sp² hybridised orbitals, one valence electron resides on each carbon centre in a p_z orbital which sits perpendicular to the other three sigma bonds, with the overall effect being a delocalised set of electron orbitals that stretches the length of the polymer. When some of the electrons are removed from the delocalised p-orbitals through oxidation, a one-dimensional electronic band is formed, and the delocalised electrons become mobile along the length of the polymer, thereby allowing the polymer to carry an electrical current.

[00050] Without being bound to theory, an advantage of producing an intrinsically conductive polymer in an electrochemical process is that the anode is not electrically shielded as the reaction progresses. Generally, if an insulating or non-conducting polymer is produced via electrochemical-induced polymerisation and the polymer that is produced is adhered to the surface of the anode, the anode becomes electrically shielded by the insulating polymer, thereby resulting in less oxidised monomers being produced and essentially quenching the polymerisation process until the polymer is removed or anode replaced. However, when a conductive polymer is produced at, and is in electrical contact with, the anode, electrons can still access the anode via the conductive polymer, thereby extending the time that the polymerisation reaction can progress before replacing the anode or harvesting the polymer from the anode.

[00051] Any conductive polymer that can be formed via anodic oxidative polymerisation may be suitable to use in an electrolytic cell of the present invention. For instance, the conductive polymer may be formed by an addition polymerisation reaction and comprise a monomer selected from the group consisting of aniline, pyrrole, thiophene, 3,4-ethylenedioxythiophene and indole and their derivatives. By the term “derivatives”, it is meant that the monomer may include substitution of any hydrogen atom that is not involved in polymerization with any suitable group. By way of example, it is understood that the amine group of one aniline molecule, and the position para to the amine group of another aniline molecule, react to produce polyaniline (see Scheme 1 below). Therefore, substitution of aniline monomers at either, or both, of the ortho or meta positions (relative to the amine group) may be carried out to produce a conductive polymer. Suitable substituents include, for example, any electron withdrawing group or any electron donating group, or any electrically neutral, or non-polar, group. In instance, the monomer may be substituted at any suitable position by at least one of halogen (e.g., F, Cl, Br or I), a cyano group (-CN), a carbonyl group, a nitro group (-NO3), an alkyl group, an alkenyl group, an alkynyl group, an alcohol group, or an amino group. The carbonyl group may be an aldehyde of general formula -RCOH, or it may be a ketone of general formula RCOR’. The alcohol group may be of general formula -ROH. The amino group may be a primary amine of general formula -NH2, or it may be a secondary amine of general formula -NHR, or it may be a tertiary amine of general formula -NRR’. The alkyl group may be a straight chain or a branched chain of single-bonded carbon atoms. The alkenyl group may be a straight chain or a branched chain of carbon atoms that includes at least one carbon-to-carbon double bond. The alkynyl group may be a straight chain or a branched chain of carbon atoms that includes at least one carbon-to-carbon triple bond. Each R or R’ group described above may itself be any suitable substituent, such as a halogen, a carbonyl group, a nitro group, an alkyl group, an alkenyl group, an alkynyl group, an alcohol group, or an amino group. Each carbonyl group, alkyl group, alkenyl group, alkynyl group, alcohol group or amino group may be further optionally substituted with any suitable heteroatom (e.g., N, O or S), or with any suitable substituent group described herein. For example, a carbonyl group may be substituted with an amino group so as to form an amido group, or a carbon atom in an alkyl group may be substituted with an oxygen atom to form an ether group. Each carbonyl group, alkyl group, alcohol group or amino group may comprise at least 1 carbon atom. Each alkenyl group or alkynyl group may comprise at least two carbon atoms. The resulting conductive polymer may therefore be one of the homogenous polymers selected from polyaniline, polypyrrole, polythiophene, poly(3,4- ethylenedioxy thiophene), and polyindole or derivatives thereof, when a solution containing a single monomer species is used. In some embodiments, two or more different monomers may be present in the electrolyte and therefore in electrical contact with the anode, resulting in the production of conductive random block co -polymers. [00052] In one embodiment of the present invention, the conductive polymer produced at the anode is polyaniline. Polyaniline may be particularly suited to use in the electrolytic cell of the present invention, as it is known to be between 10 and 1000 times more expensive than oxygen gas, meaning that a greater economic advantage is achieved. Like all of the conductive polymers that are formed via anodic oxidative polymerisation, it is understood that aniline requires an acidic environment in order to electrochemically form the polymerisation initiating radial cation species, as well as to partially oxidise the formed polyaniline so that the polymer is conductive. As an example of a more general scheme for producing conductive polymers using electrolysis, the reactions involved in the polymerisation of aniline are provided below in Scheme 1.

Scheme 1: Polymerisation of aniline and conductivity of polyaniline

A

Polyaniline Initiation

[00053] Advantageously, the theoretical potential required for the anodic oxidation of organic monomers suitable for forming a conductive polymer, such as aniline, to form the reactive radical cation is less than the theoretical potential required to drive the OER. By reducing the voltage required to drive the anodic reaction, the potential bias required across the entire electrolytic cell to produce hydrogen gas at the cathode and a polymer at the anode is reduced compared to the traditional water- splitting reaction. The potential required to initiate polymerisation may be between about 0.4 and about 1.8 V, for example the voltage required may be between about 0.5 V and 0.7 V, or about 0.6 V and about 0.8V, or about 0.75 V and about 1.25 V, or about 1 V and about 1.8 V, or about 0.4 V, 0.45 V, 0.5 V, 0.55 V, 0.6 V, 0.65 V, 0.7 V, 0.75 V, 0.8 V, 0.85 V, 0.9 V, 0.95 V, 1 V, 1.05 V, 1.1 V, 1.15 V, 1.2 V, 1.25 V, 1.3 V, 1.35 V, 1.4 V, 1.45 V, 1.5 V, 1.55 V, 1.6 V, 1.65 V, 1.7 V, 1.75 V and 1.8 V. In use with an electrolytic cell, the actual voltage bias required may be greater than the theoretical voltage, due to the additional activation energy barrier required to oxidise the monomer and produce a free radical monomer species.

[00054] In some embodiments, a redox mediator may also be required for efficient use of the electrolytic cell described herein. As the skilled person would appreciate, a redox mediator is a compound or chemical system with electrochemical activity. Redox mediators may, for example, exchange electrons with other components of a reaction, before being replenished through oxidation. In terms of the present invention, a redox mediator may be used to oxidize the monomer in solution rather than at the surface of the anode, leading to a polymer being formed in solution rather than being adhered to the anode material (which may happen when the anodic oxidation of the monomer occurs at the anode). For example, in some circumstances, the polymer produced at the anode may act to at least partially shield the anode from the electrolytic solution, thereby negatively affecting the efficiency of the cell. Suitable redox mediators may include, for example, organic compounds (such as dichlorophenolindophenol, p-benzoquinone, o-phenylenediamine and 3,4-dihydroxybenzaldehyde), transition metal complexes (such as potassium hexacyanoferrate(II) or other ferrous ion complexes) or inorganic compounds (such as triiodide ions). In one preferred embodiment, the redox mediator is triiodide (I3 ). When used with the electrolytic cell described herein, without being bound to theory it is understood that the triiodide ion oxidizes the monomer in the anodic oxidation step and is reduced to iodide, which in turn is oxidized by the anode back to the triiodide ion. This is shown in Scheme 2 below, which shows a modified first step compared to Scheme 1 above. Scheme 2: Example oxidation of aniline by using a redox mediator (triiodide)

A

[00055] As can be seen from Scheme 2, when a redox mediator is used, the monomer is initially oxidised by a triiodide ion, which initiates the polymerisation reaction. The reduced iodide ions are then oxidized at the anode, allowing for continuous oxidation of the monomer. It is noted that triiodide is used in the above scheme as an example only; any suitable redox mediator capable of oxidizing a monomer described herein and being oxidized from its reduced form by a voltage obtainable by solar methods may be used in the present invention.

Electrolytic Cell

[00056] The present invention relates to the use of an electrolytic cell. As the skilled person would understand, an electrolytic cell is an electrochemical cell that uses electrical energy to drive a non- spontaneous redox reaction. In other words, energy is supplied to an electrolytic cell in order to overcome an energy barrier that would otherwise prevent a chemical reaction from occurring. In this regard, an electrolytic cell is the opposite of a galvanic cell or voltaic cell, which produces an electrical current by harnessing spontaneous redox reactions.

[00057] Generally, an electrolytic cell is comprised of at least an anode, a cathode, an electrolyte that is in fluid contact with both the anode and cathode, and a source of electrical current that is in electrical contact with the anode and cathode. When an electrolytic cell is in use, an oxidation reaction occurs at the anode (which is the negative, or electron-producing, electrode; also referred to as the ‘working electrode’ (WE)) and a reduction reaction occurs at the cathode (which is the positive, or electron-deficient, electrode; also referred to as the ‘counter electrode’ (CE)). The counter electrode may also act as a reference electrode (RE) in a two-electrode electrolytic cell, which is a common arrangement of electrolytic cells.

[00058] One embodiment of an electrolytic cell of the present invention is provided in Figure 1. In this arrangement, a container 100 is provided for holding the electrolyte solution 102. The anode 104 and cathode 106 are in fluid contact with the electrolyte solution 102. In this arrangement, the anode 104 is optionally in electrical contact with a multimeter 110 for measuring the current of the cell during use. When present, the multimeter 110 is in electrical contact with the electricity source 116, which is in turn in electrical contact with the cathode 106. Where the multimeter 110 is absent, the anode 104 is directly in electrical contact with the electricity source 116. As mentioned above, in this two-electrode arrangement, the cathode 106 acts as both the counter electrode and the reference electrode, therefore requiring two connections to the multimeter 110 (i.e., 114 and 112 respectively) when present. In a three- electrode arrangement, a suitable reference electrode would also be in fluid contact with the electrolyte 102 and in electrical contact with the multimeter 110. If the voltage of the electrolytic cell is not measured during operation. A reference electrode 112 is not required.

[00059] Another embodiment of an electrolytic cell of the present invention is provided in Figure 2. In the electrolytic cell of Figure 2, the anode 204 is also the electricity source. In other words, the electricity source 116 of Figure 1 is placed in fluid contact with the electrolyte solution 102 and the negative terminal of the electricity source 116 is in electrical contact with the cathode 106, thereby also acting as the anode 104 of Figure 1. The electricity source 204 is optionally in electrical contact with the multimeter 110, which when present, is also in electrical contact with the cathode 106, which operates as both the reference electrode 112 and the counter electrode 114. Alternatively, a separate reference electrode may be in fluid contact with the electrolyte solution 102 in a three-electrode arrangement. If the multimeter 110 is not present, the electricity source 204 is directly in electrical contact the cathode 106. In this arrangement, the reference electrode 112 would not be required as the voltage is not measured.

[00060] Another embodiment of an electrolytic cell of the present invention is provided in Figure 3. In the electrolytic cell of Figure 3, the cathode 206 is also the electricity source. In other words, the electricity source 116 of Figure 1 is placed in fluid contact with the electrolyte solution 102 and the positive terminal of the electricity source 116 is in electrical contact with the anode 104, thereby also acting as the cathode 106, which operates as both the reference electrode 112 and the counter electrode 114, of Figure 1. The electricity source 206 is optionally in electrical contact with the multimeter 110, which when present, is also in electrical contact with the anode 104. Alternatively, a separate reference electrode may be in fluid contact with the electrolyte solution 102 in a three-electrode arrangement. If the multimeter 110 is not present, the electricity source 206 is directly in electrical contact the anode 104. In this arrangement, the reference electrode 112 would not be required as the voltage is not measured.

[00061] Each of the features of the electrolytic cell of the present invention are described in more detail below.

Electrolyte Solution

[00062] Electrolytes are used commonly in electrolytic cells, galvanic cells and voltaic cells. As the skilled person would understand, an electrolyte is a substance that forms ions when dissolved in water (or certain other solvents that results in dissociation of the ions, which may be referred to as an ionizing solvent) to produce an electrically conducting solution. Substances that may be considered to be electrolytes include acids, bases and salts.

[00063] Accordingly, with reference to Figure 1 for example, the electrolyte solution 102 of the electrolytic cell of the present invention allows for the anode 104 and cathode 106 to be in electrical contact to close the electrical circuit. Specifically, the oxidation reaction at the anode (either an OER or a polymerisation reaction) produces electrons and hydrogen cations, whereby the electrons are drawn to the cathode via the electricity source 116, and the hydrogen cations remain in the electrolyte and migrate to the cathode 106 through the electrolyte 102.

[00064] The electrolyte solution of the present invention may comprise or consist of water, or it may comprise or consist of another solvent capable of dissociating an electrolyte substance (also referred to herein as an ionizing solvent), or it may be a mixture of water and at least one other solvent. In a preferred embodiment, the electrolyte solution is a liquid which allows for the unhindered migration of hydrogen cations to the cathode as well as the release of hydrogen gas for collection from the electrolytic cell.

[00065] As mentioned above, in the electrolyte solution used in the electrolytic cells of the present invention, at least one monomer is also dissolved so as to be in electrical contact with the anode. The at least one monomer may be dissolved in the water or ionizing solvent, or it may be dissolved in another organic solvent that is miscible with water or the ionizing solvent of the electrolyte solution and then mixed with the electrolyte solution. The at least one monomer may be added to the water or the ionizing solvent as a solid and mixed with stirring or agitation until dissolved. Before use in the electrolytic cell of the present invention, the at least one monomer may be dissolved in the electrolyte solution at a concentration of between about 0.005 M and about 1 M, or between about 0.05 M and about 0.5 M, or between about 0.1 M and about 0.4 M, or at a concentration of about 0.005 M, 0.01 M, 0.02 M, 0.03 M, 0.04 M, 0.05 M, 0.06 M, 0.07 M, 0.08 M, 0.09 M, 0.1 M, 0.11 M, 0.12 M, 0.13 M, 0.14 M, 0.15 M, 0.16 M, 0.17 M, 0.18 M, 0.19 M, 0.2 M, 0.21 M, 0.22 M, 0.23 M, 0.24 M, 0.25 M, 0.26 M, 0.27 M, 0.28 M, 0.28 M, 0.29 M, 0.3 M, 0.31 M, 0.32 M, 0.33 M, 0.34 M, 0.35 M, 0.36 M, 0.37 M, 0.38 M, 0.39 M, 0.4 M, 0.41 M, 0.42 M, 0.43 M, 0.44 M, 0.45 M, 0.46 M, 0.47 M, 0.48 M, 0.49 M, 0.5 M, 0.51 M, 0.52 M, 0.53 M, 0.54 M, 0.55 M, 0.56 M, 0.57 M, 0.58 M, 0.59 M, 0.6 M, 0.61 M, 0.62 M, 0.63 M, 0.64 M, 0.65 M, 0.66 M, 0.67 M, 0.68 M, 0.69 M, 0.7 M, 0.71 M, 0.72 M, 0.73 M, 0.74 M, 0.75 M, 0.76 M, 0.77 M, 0.78 M, 0.79 M, 0.8 M, 0.81 M, 0.82 M, 0.83 M, 0.84 M, 0.85 M, 0.86 M, 0.87 M, 0.88 M, 0.89 M, 0.9 M, 0.91 M, 0.92 M, 0.93 M, 0.94 M, 0.95 M, 0.96 M, 0.97 M, 0.98 M, 0.99 M or 1 M.

[00066] The electrolyte solution of the present invention also comprises an electrolyte substance that is dissolved in the electrolyte solution and may be at least one acid, or it may be at least one base, or it may be at least one salt, or it may be a mixture of any two or three of these. Any acid which dissociates at least partially in water and/or an ionizing solvent to form a hydrogen cation and an anion may be suitable for use in an electrolyte solution. Suitable acids include, for example: mineral acids such as hydrochloric acid (HC1), hydrobromic acid (HBr), nitric acid (HNO3), sulphuric acid (H2SO4), phosphoric acid (H3PO4), boric acid (H3BO3), hydroiodic acid (HI), perchloric acid (HCIO4), chloric acid (HCIO3); and organic acids, such as, for example, acetic acid (HC2H3O2), carbonic acid (H2CO3), formic acid (H2CO2), lactic acid (CH3CH(OH)COOH), citric acid (HOC(CO2H)(CH2CO2H)2), or any mixture thereof. Any base that dissociates at least partially in water and/or an ionizing solvent to form a cation and a hydroxyl anion may be suitable for use in an electrolyte solution. Suitable bases include, for example: inorganic metal hydroxides such as sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH), barium hydroxide (Ba(OH)2) and calcium hydroxide (Ca(OH)2); or organic bases, such as ammonia (NH3), tetramethylammonium hydroxide ((CH3)- 4NOH), tetraethylammonium hydroxide ((C2Hs)4NOH), pyridine (C5H5N), or any mixture thereof. Any salt that dissociates at least partially in water and/or an ionizing solvent to form a cation and an anion may be suitable for use in an electrolyte solution. Suitable salts include, for example: metal halides (for example, sodium chloride (NaCl), potassium bromide (KBr), magnesium chloride (MgCh), copper (II) chloride (CuCh), and the like); metal sulphates (for example, sodium sulphate (Na2SO4), magnesium sulphate (MgSC ), zinc sulphate (ZnSC ), potassium sulphate (KSO4) and the like); metal nitrates (for example, potassium nitrate (KNO3), sodium nitrate (NaNCh), silver nitrate (AgNOs) and the like); and organic salts (for example, sodium acetate (CHsCOONa), sodium bicarbonate (NaHCCh) and the like).

[00067] With reference to Scheme 1 above, one of the requirements for the anodic oxidation polymerisation of a monomer (such as aniline) to produce a conductive polymer (such as polyaniline) is the presence of an acid in the electrolyte solution. In other words, whilst other electrolyte substances may be present in the electrolyte solution, at least one acid must be present, and the electrolyte solution must be at an acid pH, which is generally defined as being less than 7, or it may be less than about 6, or less than about 5, or less than about 4, or less than about 3, or the pH of the electrolyte solution may be between 0 and 7, or between about 1 and about 6, or between about 2 and 5, or the pH may be about 0, 1, 2, 3, 4, 5, 6 or 7. Without being bound to theory, it is understood that the pH of the electrolyte solution should be less than the pKa required to form the protonated monomer, as it is the protonated monomer that is oxidised at the anode to from the cationic radical species required for polymerisation. Preferably, the acid is not capable of interfering in or quenching the polymerisation reaction (i.e., the acid is not capable of being oxidised at the anode to form a reactive radical). The acid may be a mineral acid (e.g., an inorganic acid). The mineral acid may be completely ionised when dissolved in the water and/or ionizing solvent of the electrolyte solution. The mineral acid may be selected from the group consisting of hydrochloric acid (HC1), hydrobromic acid (HBr), nitric acid (HNO3), sulphuric acid (H2SO4), phosphoric acid (H3PO4), boric acid (H3BO3), perchloric acid (HCIO4) or any mixture thereof. The acid may be an organic acid. The organic acid may completely dissociate, or it may partially associate when dissolved in the water and/or ionizing solvent of the electrolyte solution. The organic acid may be selected from acetic acid (HC2H3O2), carbonic acid (H2CO3), formic acid (H2CO2), lactic acid (CH3CH(OH)COOH), citric acid (HOC(CO2H)(CH2CO2H)2), or any mixture thereof. In one embodiment, the organic acid may be acetic acid (HC2H3O2). The acid may comprise a mixture of acids, for example it may comprise two or more mineral acids, or two or more organic acids, or it may comprise a mineral acid and an organic acid, or it may comprise two or more mineral acids and an organic acid, or it may comprise two or more organic acids and a mineral acid. For example, the acid may comprise sulphuric acid (H2SO4) and acetic acid acetic acid (HC2H3O2).

[00068] However, it would also be appreciated by the skilled person that certain electrolyte substances may not be suitable for use in an electrolytic cell. For example, halide salts or acids when dissolved to form an electrolyte solution may produce halogen gas under electrolytic conditions, or organic acids, bases or salts may interfere with other reactions occurring at either the anode or the cathode. Therefore, in one preferred embodiment of the present invention, the electrolyte substance is sulphuric acid (H2SO4), which beneficially can dissociate to liberate one hydrogen cation (i.e., H⁺ + HSO4 ) or two hydrogen cations (i.e., 2H⁺ + SO4²’).

[00069] Electrolyte substances may be dissolved in the electrolyte solution in any amount suitable to achieve the conductance of electricity through it. The amount of electrolyte substances required may vary depending on factors such as: the ionization constant, pKa or pKb of the substance; the operating temperature, pH and/or voltage of the electrolytic cell; and the volume of electrolyte solution required. The total concentration of the electrolyte substances that is dissolved in the electrolyte solution may be between about 0.001 M and about 2 M, for instance it may be between 0.001 M and about 1 M, or between about 0.05 M and about 0.5 M, or between about 0.1 M and about 0.75 M, or between about 0.2 M and about 0.8 M, or between about 0.5 M and about 1.5 M, or between about 1 M and about 1.75 M, or any suitable range therein, or it may be about 0.001M, 0.005M, 0.01 M, 0.02 M, 0.03 M, 0.04 M, 0.05 M, 0.06 M, 0.07 M, 0.08 M, 0.09 M, 0.1 M, 0.11 M, 0.12 M, 0.13 M, 0.14 M, 0.15 M, 0.16 M, 0.17 M, 0.18 M, 0.19 M, 0.2 M, 0.21 M, 0.22 M, 0.23 M, 0.24 M, 0.25 M, 0.26 M, 0.27 M, 0.28 M, 0.28 M, 0.29 M, 0.3 M, 0.31 M, 0.32 M, 0.33 M, 0.34 M, 0.35 M, 0.36 M, 0.37 M, 0.38 M, 0.39 M, 0.4 M, 0.41 M, 0.42 M, 0.43 M, 0.44 M, 0.45 M, 0.46 M, 0.47 M, 0.48 M, 0.49 M, 0.5 M, 0.51 M, 0.52 M, 0.53 M, 0.54 M, 0.55 M, 0.56 M, 0.57 M, 0.58 M, 0.59 M, 0.6 M, 0.61 M, 0.62 M, 0.63 M, 0.64 M, 0.65 M, 0.66 M, 0.67 M, 0.68 M, 0.69 M, 0.7 M, 0.71 M, 0.72 M, 0.73 M, 0.74 M, 0.75 M, 0.76 M, 0.77 M, 0.78 M, 0.79 M, 0.8 M, 0.81 M, 0.82 M, 0.83 M, 0.84 M, 0.85 M, 0.86 M, 0.87 M, 0.88 M, 0.89 M, 0.9 M, 0.91 M, 0.92 M, 0.93 M, 0.94 M, 0.95 M, 0.96 M, 0.97 M, 0.98 M, 0.99 M, 1 M, 1.05 M, 1.1 M, 1.15 M, 1.2 M, 1.25 M, 1.3 M, 1.35 M, 1.4 M, 1.45 M, 1.5 M, 1.55 M, 1.6 M, 1.65 M, 1.7 M, 1.75 M, 1.8 M, 1.85 M, 1.9 M, 1.95 M, or 2M or any amount therein. In one embodiment, the electrolyte substance dissolved in the electrolyte solution is sulphuric acid (H2SO4) and may be at a concentration of the between about 0.25 M and about 2 M. [00070] The volume of the electrolyte solution may be any suitable volume that completely immerses the anode and the cathode, with enough distance between the anode and the electrode to ensure that an arc does not occur. The volume of the electrolyte solution required may be dependent on the overall design of the electrolytic cell, including the size and dimensions of the anode and cathode, the material used for the cathode and anode, the output of hydrogen gas required and the size of the electrolyte solution container. Accordingly, the volume of the electrolyte solution in an electrolytic cell of the present invention may be between about 20 mL and about 1000 L, or it may be between about 50 mL and 1 L, or between about 100 mL and about 500 mL, or between about 200 mL and 2 L, or between about 500 mL and about 5 L, or between about 1 L and about 20 L, or between about 5 L and about 50 L, or between about 10 L and 75 L, or between about 50 L and 100 L, or between about 100 L and 500 L, or between about 250 L and 750 L, or between about 200 L and 1000 L, or any range therein. For example, the volume of the electrolyte solution may be 10 mL, 15 mL, 20 mL, 25 mL, 30 mL, 35 mL, 40 mL, 45 mL, 50 mL, 55 mL, 60 mL, 65 mL, 70 mL, 75 mL, 80 mL, 85 mL, 90 mL, 95 mL, 100 ml, 105 mL, 110 mL, 115 mL, 120 mL, 125 mL, 130 mL, 135 mL, 140 mL, 145 mL, 150 mL, 155 mL, 160 mL, 165 mL, 170 mL, 175 mL, 180 mL, 185 mL, 190 mL, 195 mL, 200 mL, 210 mL, 220 mL, 230 mL, 240 mL, 250 mL, 260 mL, 270 mL, 280 mL, 290 mL, 300 mL, 310 mL, 320 mL, 330 mL, 340 mL, 350 mL, 360 mL, 370 mL, 380 mL, 390 mL, 400 mL, 410 mL, 420 mL, 430 mL, 440 mL, 450 mL, 460 mL, 470 mL, 480 mL, 490 mL, 500 mL, 510 mL, 520 mL, 530 mL, 540 mL, 550 mL, 560 mL, 570 mL, 580 mL, 590 mL, 600 mL, 610 mL, 620 mL, 630 mL, 640 mL, 650 mL, 660 mL, 670 mL, 680 mL, 690 mL, 700 mL, 710 mL, 720 mL, 730 mL, 740 mL, 750 mL, 760 mL, 770 mL, 780 mL, 790 mL, 800 mL, 810 mL, 820 mL, 830 mL, 840 mL, 850 mL, 860 mL, 870 mL, 880 mL, 890 mL, 900 mL, 910 mL, 920 mL, 930 mL, 940 mL, 950 mL, 960 mL, 970 mL, 980 mL, 990 mL, 1 L, 1.1 L, 1.2 L, 1.3 L, 1.4 L, 1.5 L, 1.6 L, 1.7 L,

1.8 L, 1.9 L, 2 L, 2.1 L, 2.2 L, 2.3 L, 2.4 L, 2.5 L, 2.6 L, 2.7 L, 2.8 L, 2.9 L, 3 L, 3.1 L, 3.2 L,

3.3 L, 3.4 L, 3.5 L, 3.6 L, 3.7 L, 3.8 L, 3.9 L, 4 L, 4.1 L, 4.2 L, 4.3 L, 4.4 L, 4.5 L, 4.6 L, 4.7 L,

4.8 L, 4.9 L, 5 L, 5.1 L, 5.2 L, 5.3 L, 5.4 L, 5.5 L, 5.6 L, 5.7 L, 5.8 L, 5.9 L, 6 L, 6.1 L, 6.2 L,

6.3 L, 6.4 L, 6.5 L, 6.6 L, 6.7 L, 6.8 L, 6.9 L, 7 L, 7.1 L, 7.2 L, 7.3 L, 7.4 L, 7.5 L, 7.6 L, 7.7 L,

7.8 L, 7.9 L, 8 L, 8.1 L, 8.2 L, 8.3 L, 8.4 L, 8.5 L, 8.6 L, 8.7 L, 8.8 L, 8.9 L, 9 L, 9.1 L, 9.2 L,

9.3 L, 9.4 L, 9.5 L, 9.6 L, 9.7 L, 9.8 L, 9.9 L, 10 L, 10.5 L, 11 L, 11.5 L, 12 L, 12.5 L, 13 L,

13.5 L, 14 L, 14.5 L, 15 L, 15.5 L, 16 L, 16.5 L, 17 L, 17.5 L, 18 L, 18.5 L, 19 L, 19.5 L, 20 L,

20.5 L, 21 L, 21.5 L, 22 L, 22.5 L, 23 L, 23.5 L, 24 L, 24.5 L, 25 L, 25.5 L, 26 L, 26.5 L, 27 L,

27.5 L, 28 L, 28.5 L, 29 L, 29.5 L, 30 L, 31 L, 32 L, 33 L, 34 L, 35 L, 36 L, 37 L, 38 L, 39 L, 40 L, 41 L, 42 L, 43 L, 44 L, 45 L, 46 L, 47 L, 48 L, 49 L, 50 L, 52 L, 54 L, 56 L, 58 L, 60 L, 62 L, 64 L, 66 L, 68 L, 70 L, 72 L, 74 L, 76L, 78 L, 80 L, 82 L, 84 L, 86 L, 88 L, 90 L, 92 L, 94 L, 96 L, 98 L, 100 L, 105 L, 110 L, 115 L, 120 L, 125 L, 130 L, 135 L, 140 L, 145 L, 150 L, 155 L, 160 L, 165 L, 170 L, 175 L, 180 L, 185 L, 190 L, 195 L, 200 L, 205 L, 210 L, 215 L, 220 L, 225 L, 230 L, 235 L, 240 L, 245 L, 250 L, 255 L, 260 L, 265 L, 270 L, 275 L, 280 L, 285 L, 290 L, 300 L, 305 L, 310 L, 315 L, 320 L, 325 L, 330 L, 335 L, 340 L, 345 L, 350 L, 355 L, 360 L, 365 L, 370 L, 375 L, 380 L, 385 L, 390 L, 395 L, 400 L, 405 L, 410 L, 415 L, 420 L, 425 L, 430 L, 435 L, 440 L, 445 L, 450 L, 455 L, 460 L, 465 L, 470 L, 475 L, 480 L, 485 L, 490 L, 495 L, 500 L, 510 L, 520 L, 530 L, 540 L, 550 L, 560 L, 570 L, 580 L, 590 L, 600 L, 610 L, 620 L, 630 L, 640 L, 650 L, 660 L, 670 L, 680 L, 690 L, 700 L, 710 L, 720 L, 730 L, 740 L, 750 L, 760 L, 770 L, 780 L, 790 L, 800 L, 810 L, 820 L, 830 L, 840 L, 850 L, 860 L, 870 L, 880 L, 890 L, 900 L, 910 L, 920 L, 930 L, 940 L, 950 L, 960 L, 970 L, 980 L, 990 L or 1000 L, or any range therein.

[00071] In one embodiment, the electrolyte solution may be produced by adding or dissolving the monomers in an aqueous solution comprising at least one electrolyte substance. For example, when the electrolyte substance is at least one acid, the electrolyte solution may be produced by obtaining an acid solution comprising between about 0.01 M and about 1 M of a mineral acid, and dissolving a sufficient amount of the monomer in the acid solution to produce a solution that has a concentration of monomer of between about 0.01 M and 0.5 M. In some embodiments, the presence of an acid or a base in the electrolyte solution may assist with the dissolution of the monomer in the water or ionizing solvent. In other words, the monomer may be more soluble in an acidic or basic electrolyte solution. Without being bound to theory, some organic compounds that are not readily soluble in water in neutral form may be more soluble in an aqueous solution that is either acidic or basic solution than in pure water, particularly if the pH of the solution is less than the pKa, or greater than the pKb, of at least one ionizable substituent group on the organic compound, resulting in ionization of the compound. This effect may be more pronounced in organic molecules that have the ionizable substituent bound to an aromatic ring, whereby the ionized form of the organic compound is understood to be stabilized by the delocalised 7t-electrons on the aromatic ring. One example of an organic compound that is more soluble in cationic form (i.e., when dissolved in an acidic aqueous solution) is aniline.

[00072] The volume of the electrolyte solution may be relatively constant (i.e., only varying by up to about 10%, or about 5%, or about 2%, or about 1% of the starting volume) during use of the electrolytic cell, or it may increase over time as electrolyte solution is added to the electrolytic cell during use as components of the electrolyte solution are depleted and spent electrolyte solution is not removed. In other words, the electrolytic cell of the present invention may be operated in a batch mode or a continuous mode. Under a batch mode operation, it is understood that the electrolytic cell is operated for a period of time on a scale of minutes to hours before the electrolyte solution, and any other components such as the cathode or the anode, are replaced, and/or the product made at the cathode is harvested, before recommencing operation of the electrolytic cell. The period of time that the electrolytic cell may operate may be limited by the amount of monomer present in the electrolyte solution. The period of time that an electrolytic cell is operated under batch mode may be between about 1 minute and about 24 hours, or between about 5 minutes and 60 minutes, or between about 30 minutes and about 2 hours, or between 45 minutes and about 6 hours, or between about 4 hours and about 12 hours, or between 12 hours and about 18 hours, or for a period of time of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59 or 60 minutes or about 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 or 24 hours or any range therein. The period of operation during batch mode may be constant between operation cycles or it may be variable and dependent on factors such as electricity input, hydrogen gas production, temperature, or condition of the cathode and/or the anode material. Under a continuous mode operation, it is understood that the electrolytic cell is operated for a period of time on a scale of days, weeks or months and the electrolyte may be continuously or regularly added to the electrolyte cell during operation, and any solid product produced is regularly harvested during operation. The period of time that an electrolytic cell is operated under continuous mode may be between about 1 day and about 90 days, or between about 2 days and 60 days, or between about 7 days and 30 days, or between about 14 days and about 75 days, or for a period of time of about 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50 , 51, 52, 53, 54, 55, 56, 57, 58,

59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83,

84, 85, 86, 87, 88, 89, or 90 days. However, the skilled person would be aware that even under a continuous mode of operation, the electrolytic cell may need to be stopped occasionally for maintenance. Likewise, if the electrolytic cell is to be operated in a continuous mode and an electricity source is used that has a variable output over time, such as a solar cell which would have a zero-voltage output when not illuminated, the electrolytic cell would need to have access to an alternative electricity source, such as a battery for storing excess solar energy, or an alternative means of electricity generation, such as a wind turbine, wave power generator, mains power, a gas turbine, a nuclear reactor or the like. Preferably, all of the electricity provided to the electrolytic cell would be from a renewable source, such as from solar energy, wind energy, wave energy or similar technologies. Further, it will be evident to the skilled person that if a redox mediator is used, operation in batch mode may be most suitable so that the polymer has sufficient time in solution to polymerise. Replacement of the electrolyte solution in continuous mode would also likely remove the polymer product formed in solution if a redox mediator is used.

[00073] In some embodiments, the electrolyte solution may be collected, rather than produced. In other words, rather than being produced by dissolving monomers in a solvent and adding other components, such as acid(s), bases(s), salt(s) and the like, the electrolyte solution may be collected from a source that comprises or contains at least a monomer capable of forming a conductive polymer. By way of a non-limiting example, an electrolyte solution containing or comprising aniline may be collected from the wastewater stream of an industrial facility, such as a manufacturer of dyed fabrics, or a leather tannery, or the like. As the skilled person would appreciate, such a wastewater sample may need to be treated before contact with the electrolytic cell described herein. Such treatment may include, for example: filtration, flocculation, or settling in order to remove suspended solids or bacteria; the addition of acid(s) to reduce the pH to at least less than 7; and chelator treatment to remove dissolved metal species. In some embodiments, the wastewater stream may be contacted with the electrolytic cell of the present invention in a batch mode, whereby the wastewater is collected, treated and then contacted with the electrolytic cell described herein. In other embodiments, the wastewater stream may be contacted with the electrolytic cell of the present invention in a continuous mode, whereby the wastewater is treated and continually passes through the electrolytic cell described herein, which may be particularly useful as a “polishing” step (that is, where the wastewater stream has been treated to remove or reduce other components). It is expected that the skilled person would be able to optimise the process for either mode of operation.

Electricity Source

[00074] The electrolytic cell of the present invention requires a source of electricity in order to function. As mentioned above, an electrolytic cell is not spontaneous like a galvanic cell or voltaic cell and requires an input of an electrical current to drive the energetically unfavourable reaction at the anode. [00075] Any suitable source of electricity may be used in the electrolytic cell of the present invention. The electricity source must be capable of producing a voltage that is at least equivalent to, or preferably more than, the potential required to drive the oxidation reaction at the anode. In some embodiments, the electricity source must be capable of producing a voltage of least about 0.4 V, or between about 0.5 V and about 1.8 V, or between about 0.8 V and about 1 V, or about 0.4 V, 0.45 V, 0.5 V, 0.55 V, 0.6 V, 0.65 V, 0.7 V, 0.75 V, 0.8 V, 0.85 V, 0.9 V, 0.95 V, 1 V, 1.05 V, 1.1 V, 1.15 V, 1.2 V, 1.25 V, 1.3 V, 1.35 V, 1.4 V, 1.45 V, 1.5 V, 1.55 V, 1.6 V, 1.65 V, 1.7 V, 1.75 V, or 1.8 V.

[00076] In some preferred embodiments, the electricity source derives electricity from a renewable energy source. By “renewable”, it is meant that the energy source is sustainable and not depleted when used. Examples of a renewable energy source include, for example, solar power, wind power, tidal power, hydropower and geothermal heat. Accordingly, the electricity source of these embodiments must be capable of converting at least one source of renewable energy into an electrical current. In one embodiment, the electricity source may convert solar power into electricity. The electricity source may use photovoltaic (PV) technology to convert photons of light directly into electricity (i.e., it may be a photovoltaic device), or it may be a thermal process which utilises heat energy from the sun to drive a turbine and generate electricity. In one preferred embodiment, the electricity source may comprise at least one photovoltaic cell, or it may comprise two or more photovoltaic cells arranged in series. The photovoltaic cell or device may be a silicon-based cell, or it may be a thin-film solar cell (for example, a copper indium gallium selenide (CIGS) cell or a copper zinc tin sulfide (CZTS) cell), or it may be a perovskite cell, or it may be a multi-j unction cell (for example, a combined tandem solar cell), or it may be III-V cell, or it may be a dye- sensitized cell, or it may comprise colloidal quantum dots, or it may comprise organic polymers or other organic molecules, or it may comprise or consist of a semiconductor-based material, for example, titanium dioxide (TiO- 2), zinc oxide (ZnO), tungsten trioxide (WO3), bismuth vanadate (BiVCU), iron(III) oxide / a- hematite (Fe2O3), gallium nitride (GaN) or any other suitable superconductor-based photoactive material, or it may be based on any other suitable photovoltaic technology capable of providing the required voltage when illuminated.

[00077] In some embodiments, such as that represented by Figure 1, the electricity source 116 may be arranged so as to be in electrical contact with the anode 104 and cathode 106, and optionally a multimeter 110 for measuring the voltage and current of the electrolytic cell. In such embodiments where the electricity source is a photovoltaic cell or device, the electrolytic cell must be arranged so as to illuminate the at least the photovoltaic device with sunlight.

[00078] In other embodiments, such as that represented by Figure 2, the electricity source may also act as the anode 204. In particular, in such embodiments, the electricity source, such as a photovoltaic device or cell, or a photoactive material such as a semiconductor material, is in electrical contact with the cathode 106 and optionally with a multimeter 110, and is in fluid contact with the electrolyte solution 102, yet must still be arranged so as to be able to be illuminated by a light source, such as sunlight. In other embodiments, such as the represented bu Figure 3, the electricity source may also act as the cathode 206. In particular, in such embodiments, the electricity source, such as a photovoltaic device or cell, or a photoactive material such as a semiconductor material, is in electrical contact with anode 104 and optionally with a multimeter 110, and is in fluid contact with the electrolyte solution 102, yet must still be arranged so as to be able to be illuminated by a light source, such as sunlight. When the electrolytic cell is used in these arrangements (i.e., when the anode is a photoanode or when the cathode is a photocathode, and is illuminated with a light source, such as sunlight), the electricity source also acts as either the working electrode and is therefore the site that the oxidative polymerisation reaction occurs (when a photoanode of Figure 2) or the electricity source is a photoanode and acts as the counter electrode, and optionally the reference electrode. As the skilled person may appreciate, such arrangements may provide efficiencies in manufacturing. For instance, when a photoanode is used, it may allow for the coating of a photovoltaic cell or device directly with a polymer, such as a conducting polymer or a conductive polymer, without the need to first produce the polymer, and then apply it to a photovoltaic cell or device in a separate step. The polymer produced may be formed directly on the photovoltaic cell or device, such as on the photoactive surface, on a non-photoactive surface or on both types of surfaces. The polymer may be formed on any conductive surface of the photovoltaic cell or device. The polymer may be formed so as to completely, or substantially, or partially, coat the entire photoactive surface of the photovoltaic cell or device. When the polymer is formed on at least a portion of the photoactive surface and the produced polymer is not optically transparent (i.e., whereby the polymer absorbs and/or reflects light so as to give a coloured appearance), the process may be optimised by the skilled person to avoid excessive darkening or coating of the photoactive portion of the photovoltaic cell or device by the produced polymer, which may reduce the efficiency of the photovoltaic cell or device over time. Anode

[00079] The anode of the electrolytic cell of the present invention is the negative electrode, which is the site whereby the oxidative polymerisation reaction is initiated and the conductive polymer is formed, or whereby a component of the redox mediator is oxidized, allowing for further oxidation of the monomer. The anode may be formed from a range of materials, depending on the arrangement of the electrolytic cell and the product that is to be produced.

[00080] In one arrangement, and with reference to Figure 1 or Figure 3, the anode 104 may comprise or consist of any conductive material suitable for use as a working electrode. Preferably, the anode is not rapidly consumed or degraded during use of the electrolytic cell. The anode material may comprise or consist of a conductive glass (for example, a fluorine- doped tin oxide glass), or the anode material may comprise or consist of a metal or an alloy of metals (for example, nickel, titanium, platinum, gold, stainless steel) in the form of a sheet or a foam, or the anode material may comprise or consist of a graphite film, a graphite sheet, or a carbon nanotube, or the anode material may be another suitable material. The anode material may be a mixture of materials, for example it may be a metal sheet or a conductive glass coated with a graphite sheet, or it may be an alloy of different metals. In the representative arrangement of Figure 1, the anode is in electrical contact with the electricity source 116 and optionally a multimeter 110, and is in fluid contact with the electrolyte solution 102. The size, shape and dimensions of the anode may be optimised by the skilled person to suit the overall design of the electrolytic cell. In this arrangement, the desired product of the electrolytic cell may be the conductive polymer produced (which is removed from the anode, processed and used to make other products) or it may be the combination of the anode and the conductive polymer (which are processed together to form a conductive material for use in other products). For instance, it is invisioned by the inventors that the electrolytic cell described herein could be used to produce a conductive polymer-coated graphite or metal anode that could be processed together to form a composite material with excellent conductive properties. Such conductive composite materials may have utility in a number of products, including for example as an anode in a battery, such as in a flow-cell battery, fuel cells, organic -based electronics (such as organic photovoltaic cells or flexible thin film circuits) or the like.

[00081] In another arrangement, and with reference to Figure 2, the anode 204 may comprise or consist of the electricity source, as herein defined. In another embodiment, the anode 204 may comprise or consist of a semiconductor-based photoanode material, for example, titanium dioxide (TiCh), zinc oxide (ZnO), tungsten trioxide (WO3), bismuth vanadate (BiVC ), iron(III) oxide / a-hematite (Fe2O3), gallium nitride (GaN) or any other suitable n-type superconductorbased photoactive material. In other words, in this arrangement, the anode 204 acts as both the working electrode and the electricity source. By the term “photoanode”, it is meant that the anode material is capable of converting light energy into electrical energy. By the term “photoactive”, it is meant that the material responds to light energy and, in this instance, produces electrical energy.

[00082] Irrespective of the arrangement or material of the anode, the oxidative polymerisation reaction occurs on, or in the vicinity of, or in electrical contact with, the anode. The polymer, or conductive polymer or conducting polymer, may form on the surface of the anode as a film (i.e., parallel with the surface of the anode) or it may form as needles or protrusions (i.e., perpendicular to the surface of the anode), or it may form in a mixture of orientations attached to the anode. The polymer produced may be crystalline, or it may be semi-crystalline, or it may be amorphous. The polymer produced at the anode may be harvested from the surface of the anode, or it may detach from the anode and be collected from the electrolyte solution, or the coating of the anode material with the polymer or conducting polymer or conductive polymer may form a finished article. In other words, the product produced at the anode of the electrolytic cell of the present invention may be the polymer produced, or it may be an article that is fully, or substantially, or partially, coated with a polymer, such as a conductive polymer.

Cathode

[00083] The cathode of the electrolytic cell of the present invention is the positive electrode. It is also the site whereby the HER occurs and hence the evolution of hydrogen gas.

[00084] In one arrangement, and with reference to Figure 1 and Figure 2, the anode may be formed from any suitable material that facilitates the electrochemical production of hydrogen, preferably without significantly contributing to an overpotential. Preferably, the cathode is not rapidly consumed or degraded during use of the electrolytic cell. The cathode may be formed from any suitable conductive material. The cathode may comprise, or consist of, a metal, or the cathode may comprise, or consist of, a carbon-based conductor material (for example, graphite) or it may comprise, or consist of, a mixture of a metal and a carbon-based conductor material. The cathode may comprise or consist of a pure metal, or a metal alloy, or a metal phosphide or a metal dichalcogenide, or a graphite, or a carbon nanotube, or a mixture of any two or more of these. The cathode material may comprise or consist of, for example, a metal or metal alloy comprising or consisting of, for example, platinum, palladium, cobalt, nickel, manganese, molybdenum, rhodium, nickel-molybdenum alloy (NisMo); a metal phosphide such as cobalt phosphide (CoP), nickel phosphide (N12P), molybdenum phosphide (MoP); a metal oxide such as ruthenium (IV) oxide; a metal dichalcogenide such as cobalt diselenide (CoSe2) or molybdenum sulfide (M0S2); a carbon-based conductor material such as a graphite sheet, a graphite film, a carbon nanotube, or an mixture of any two or more of these materials.

[00085] In another arrangement, and with reference to Figure 3, the cathode 206 may comprise or consist of the electricity source, as herein defined. In another embodiment, the cathode 206 may comprise or consist of a semiconductor-based photocathode material, for example, copper (I) oxide (CU2O), p-type silicon, indium phosphide (InP) or any other suitable p-type superconductor-based photoactive material. In other words, in this arrangement, the cathode 206 acts as the reference electrode, the counter electrode and the electricity source. By the term “photocathode”, it is meant that the cathode material is capable of converting light energy into electrical energy. By the term “photoactive”, it is meant that the material responds to light energy and, in this instance, produces electrical energy.

Electrical Contacts

[00086] As discussed above, the electrolytic cell of the present invention requires at least the cathode, the anode and the electricity source to be in electrical contact, which means that an electrical current can pass from one feature to another. This allows for the movement of electrons, and hence an electrical current, through the electrolytic cell from the anode to the cathode. The electrical contact may be formed and maintained through any suitable conducting material, such as for example, wires comprising or consisting of copper, aluminium, iron, platinum, silver, gold, or a mixture of two or more of these materials.

Optional Components

[00087] As discussed above, the electrolytic cells of the present invention must include an electricity source 116 (which may also be the anode 204), a cathode 106, an anode 104 (which may also be the electricity source 204), an electrolyte solution 102, and suitable materials to maintain electrical contact between the anode and the cathode. However, the electrolytic cells of the present invention may also include additional components to assist in the operation of the cells for improved efficiency or lengthening the continual operation time.

Multimeter

[00088] The electrolytic cells of the present invention may include a multimeter 110 that is capable of monitoring the voltage and/or the current of the cell during use. The multimeter is arranged so as to be in series with the electricity source. The multimeter is in electrical contact with the anode (as the working electrode) and the cathode (as both the reference electrode and the counter electrode in the two-electrode systems of Figure 1 and Figure 2). In a three-electrode arrangement, the reference electrode is separate and in fluid contact with the electrolyte solution but is still in electrical contact with the multimeter. Any suitable multimeter may be used in the electrolytic cell of the present invention.

Storage Device

[00089] The electrolytic cell of the present invention may optionally include an electrical storage device. As the skilled person may appreciate, in certain embodiments of the present invention, the electricity source converts a renewable energy source into electricity. However, some renewable energy sources, such as solar power or wind power, cannot be utilised consistently as the energy available from these source cycle over time. For example, solar cells can only convert sunlight into electricity when illuminated during the day. Accordingly, a storage device for storing excess energy may be included in some embodiments of the present invention. Any suitable storage device may be used. For example, the storage device may be a battery that stores excess current during use of the electrolytic cell for release when the current drops below a set value. The battery may be controlled by a controller that measures the current of the electrolytic cell and releases additional electrical current as required by the electrolytic cell. In another example, the storage device may be a fuel cell that converts some of the produced hydrogen gas into electricity that is then used by the electrolytic cell. Whilst it may be expected that the use of a storage device may reduce the overall efficiency of the electrolytic cell (e.g., by increasing the electrical resistance of the system or using some of the produced hydrogen gas), this may be offset by an extension in the operation time of the electrolytic cell. It would be expected that the skilled person could suitable optimise a system incorporating a storage device.

Gas-tight Enclosure

[00090] To ensure safe collection of the hydrogen gas produced, the electrolytic cell may be located within an air-tight enclosure. This allows for the collection of hydrogen gas and, if the air-tight enclosure is purged with an inert gas before use, limits the chance that the hydrogen gas will spontaneously react with other reactive species, such as oxygen. The electricity source may be located within the air-tight enclosure or it may be located outside the air-tight enclosure. If the electricity source converts light energy into electricity (i.e., is a photovoltaic cell) and is located within the air-tight container, the air-tight container must be suitably transparent to allow the passage of light through it to the photoactive surface of the photovoltaic cell.

Light Source

[00091] As described herein, in some embodiments of the present invention the electrolytic cell may comprise a photoactive device that converts light to energy. The photoactive device may be an electricity source 116, or it may be a photoanode 204, or it may be a photocathode 206. In such embodiments, it is understood that the electrolysis cell is driven by electricity when the electricity source 116, or photoanode 204, or photocathode 206 is exposed to light. Preferably, the light source is solar light. However, when insufficient light is available from a solar source, an additional light source may be used. The additional light source may be located in the vicinity of, or near, the photoactive device. The additional light source may be any suitable source of electromagnetic radiation, such as visible or near-visible light, that is usable by the photoactive device. For example, the additional light source may be an artificial light source, such as an incandescent bulb, a fluorescent light bulb, a halogen light bulb, or at least one light emitting diode (LED), or any other suitable light source.

Stirring System

[00092] To ensure that the reaction occurring at either the cathode or the anode are not limited by the diffusion of reactants through the electrolyte solution, the electrolytic cell of the present invention may also include a stirring system. The stirring system may be any suitable system that elicits movement of the components of the electrolyte solution. The stirring system may comprise a moving portion and a non-moving portion. In such embodiments, the moving portion of the stirring system is located in fluid contact with the electrolyte solution so that, in use, the electrolyte solution, comprising at least one monomer and at least one electrolyte, is mixed and reactants are provided to the cathode and anode.

[00093] The stirring system may be in electrical contact with the photoactive device (such as the electricity source 116, or the photoanode 204, or the photocathode 206) so that the stirring system is activated when the electrolytic cell is active, although the skilled person would be aware that such an arrangement may increase the current required by the electrolytic cell. Alternatively, the stirring system may be in electrical contact with an electricity source that is separate to the electrolytic cell. For instance, the stirring system may be powered by a separate photoactive device, such as a solar cell as defined herein, or it may be powered by any other suitable electricity source, such as mains power, a battery, or another renewable energy source, such as wind power.

[00094] The stirring system may be any suitable system. For example, the stirring system may comprise a moving portion that comprises at least one blade that rotates about an axis, such as a fan. The fan may have one blade, or it may have more than one blade. The fan may be attached to an axel that is driven by an electrical motor which is not in fluid contact with the electrolyte solution. In another example, the stirring system may comprise a magnetic portion that is in fluid contact with the electrolyte and in magnetic contact with a moving portion that is located outside the electrolyte, so that in use, the moving portion rotates and drives the rotation of the magnetic portion in fluid contact with the electrolyte solution. This stirring system may be known to the skilled person as a magnetic stirrer. In another example, the stirring system may comprise a moving portion that is a pump which is in fluid contact with the electrolyte solution. The pump may be a recirculation pump. The pump may comprise and inlet and an outlet, whereby in use, the inlet draws a portion of liquid from the electrolyte solution, which is passed through the pump and is returned to the electrolyte solution in a location that is separate to the inlet, thereby creating mixing of the electrolyte solution.

Examples

Example 1 [00095] In one example, an electrolyte solution was prepared by dissolving, with stirring, an appropriate amount of a 0.1 M or 0.2 M aniline solution in 50 mL of a 0.1 M or 0.5 M solution of sulfuric acid. An electrolytic cell in two-electron configuration in accordance with Figure 1 is prepared as a proof-of concept. A multimeter was included in series so that the voltage and current could be monitored. The electricity source is two silicon-based photovoltaic cell in series, which provide a voltage bias of 1.1 V. The electrolytic cell is located within an air-tight container that is purged with helium gas for 1 hour before use.

[00096] Stable operation of the electrolytic cell was achieved for 24 hours, with illumination of the photovoltaic cell with light of 1000 Wm² (i.e., “1-Sun”) using a solar simulator. During operation, a green film is observed to be deposited on the anode over time and bubbles of hydrogen gas are observed forming on the cathode.

[00097] After operation of the electrolytic cell, the green film was collected from the anode and dried before characterisation using Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy (as shown in Figures 4A and 4B) and electron microscopy.

[00098] Figure 4A shows a number of peaks were identified in the Fourier Transform Infrared (FTIR) spectrum of the green material collected from the anode. Assignments for the main peaks are provided in Table 1.

Table 1: Main peaks from the Fourier Transform Infrared (FTIR) spectrum:

[00099] Figure 4B shows the Raman spectrum for the same green material. Assignments for the main peaks for this material as provided in Table 2. Table 2: Main peaks from the Raman spectrum:

[000100] As can be seen from Figure 4A and Figure 4B, as well as Tables 1 and 2, the green film produced at the anode shows all of the characteristic peaks expected for the base form of polyaniline, as expected from operation of the electrolytic cell whereby aniline was added to the electrolyte solution.

[000101] Another important aspect of electrolysis processes, especially those driven by renewable energy, is the efficiency of the cell. To investigate this aspect, regular measurements were taken during operation of the electrolytic cell described above during the production of polyaniline. The current (mA) was continually measured over the two-hour runtime by a multimeter connected to a datalogger, which allowed for the calculation of the Coulombic charge (C), as shown in Figure 4C. Hydrogen gas production was also sampled every ten minutes and was quantified by gas chromatography to provide millimoles of H2 gas produced per hour per litre. Comparison of the moles of hydrogen gas can be compared with the Coulombic charge (i.e., the current measured) to calculate the Faradic efficiency of the production of hydrogen. The equation for calculating the Faradic efficiency of the HER at the cathode is Faradaic efficiency

wherein n is the moles of H2 gas produced, F is the Faraday constant, 2 relates to the number of moles of electrons required per mole of H2 gas produced, and Q is the total quantity of consumed electricity. This equation was used at each H2 gas sample point to calculate the Faradic efficiency over time. As can be seen from Figures 4C and 4D, a Faradic efficiency of about 93% was obtained once a current of about 10 mA was reached for this initial proof-of- concept design. With optimisation, it is expected that a Faradic efficiency of close to 100% is achievable, as there are no significant competing side reactions.

Example 2

[000102] In some industrial settings, such as fabric dyeing and leather manufacturing, aniline is present in aqueous waste streams as a toxicant. To investigate if the solar-driven cell and processes of the present invention would be suitable for treating a wastewater stream (to both remove aniline or other suitable monomers of conductive polymers while recovering valuable polymers and hydrogen gas), an experiment was conducted using an aqueous solution containing 1.2 mg/mL of aniline (i.e., a 0.0129M solution of aniline) and 0.5 M H2SO4. The concentration of aniline was selected to mimic a typical water stream comprising aniline. The same electrolysis cell and conditions as described in Example 1 and Figure 1 was used in this experiment, including the same voltage (1.1 V) and running time (24 hours).

[000103] As shown in Figure 5a, the current density quickly increases in the first 4 h, and then gradually decrease after it reaches to the maximum current density of 9.6 mAcm'²

[000104] UV-vis absorption of the solution was used to indirectly monitor the concentration of polyaniline with time as the absorption peaks between 200 and 300 nm align with those of polyaniline at lower molecular weights (e.g., polyaniline dimers or trimers) and more deposited polyaniline on the Ti sheet electrode surface is observed in time. Figure 5b shows the gradual increase over time of polyaniline dimers and trimers in solution, indicating that polyaniline was being produced by the electrolysis cell, when powered by solar cells.

Example 3

[000105] As the skilled person would appreciate, one potential use for polyaniline, particularly as part of a composite material with a conductive carbon, silicon or metal substrate, is as an anode or cathode material for batteries. To investigate this as a potential use for the polyaniline produced by the cell of the present invention, the inventors have investigated the stability of the produced polyaniline under negative and positive potential in an acid environment to determine suitability for use in a vanadium-based flow battery. [000106] In this example, the stability of polyaniline produced by the cell of the present invention was investigated under negative (-0.4 V vs. Pt) and positive (1.8 V vs. Pt) potential in IM H2SO4 with a two-electrode configuration, simulating a vanadium-based flow battery.

[000107] After 73 hours of continuous running under negative potential at -0.4 V vs. Pt, there is only small change in the cyclic voltammogram curve (Figure 6a) and a generally constant current of between about -0.2 and about -0.27 (Figure 6b) suggesting the produced polyaniline has very good stability under negative potential (that is, when used as an anode material).

[000108] However, under positive potential conditions, after 43 hours of continuous running at 1.8 V vs. Pt the cyclic voltammogram curve was significantly degraded (Figure 7a) and the current of polyaniline reduced considerably (Figure 7b) suggesting polyaniline has poor stability under positive potential conditions.

[000109] Therefore, polyaniline produced from the cell of the present invention, either alone or produced as a composite material incorporating the polyaniline and the anode material of the cell, may be suitable for use as the anode material for a flow-cell battery, such as a vanadium- based flow battery in 1 M H2SO4. However, the polyaniline appears to be unsuitable for use as a cathode material.

Example 4

[000110] The inventors have also investigated the use of an alternative monomer system for producing a conductive polymer using the electrolytic cell of the present invention. In this example, a 21.6 mM pyrrole (PY) solution in 0.5 M HC1 was prepared and added to the same electrolytic cell arrangement as described above for aniline.

[000111] As shown in Figure 8a, whilst there was some oxidation above 0.8 V initially, after 24 hours this had dropped significantly, indicating that the polypyrrole production reaction had slowed, possibly due to shielding of the anode material. This is also shown in Figure 8b, which showed a significant decrease in current after 10 hours of continuous running at 1 V. Notably, the addition of fresh pyrrole could not recover this current density.

[000112] To improve the polymerisation of pyrrole to polypyrrole, the experiment was repeated using a redox mediator. As the skilled person would appreciate, a redox mediator is a compound or chemical system with electrochemical activity which acts to assist in the exchange of electrons in a redox reaction. Accordingly, the inventors repeated this experiment by preparing a 21.6 mM pyrrole (PY) solution in 0.4 M H2SO4, with the addition of 0.1 M HI as a redox mediator. In this system, the pyrrole monomers are polymerised to polypyrrole by the 13“ ions in solution, which reduces the 13“ ions to T ions. The anode of the electrolytic cell described herein then oxidizes the T ions back to 13“ ions, allowing for the polypyrrole to be produced in solution, rather than at the surface of the anode. This approach was applied successfully, as can be seen in Figure 9a, whereby the cyclic voltammogram curve showed little difference between running the system without pyrrole (that is, with only 0.1 M HI and 0.4 M H2SO4) and with pyrrole, suggesting that the addition of the pyrrole did not degrade the activity of the cell as seen above (contrary to Figure 8a). This conclusion is supported by Figure 9b, which shows little difference between the first and second addition of pyrrole monomer solution, compared to Figure 8b.

[000113] Therefore, the inventors have demonstrated that the electrolytic cell described herein can be adapted to produce a range of conductive polymers. Further, use of the cell can be adapted to include a redox mediator, such as iodide, in circumstances where production of the conductive polymer on the anode material may reduce the efficiency of the cell.

[000114] Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms in particular features of any one of the various described examples may be provided in any combination in any of the other described examples. Various modifications and alterations to this invention will become apparent to those skilled in the art without departing from the scope and spirit of this invention. It should be understood that this invention is not intended to be unduly limited by the illustrative embodiments and examples set forth herein and that such examples and embodiments are presented by way of example only with the scope of the invention intended to be limited only by the claims set forth herein as follows.

Claims

39 CLAIMS

1. An electrolytic cell, comprising: an electrolyte solution, comprising water, an acid and a monomer for producing a conductive polymer; an anode and a cathode in fluid contact with the electrolyte; and an electricity source, which is in electrical contact with the anode and the cathode, wherein the electricity source converts light from a light source into electricity, wherein, in use, the electricity source provides a voltage to the electrolytic cell that is sufficient to oxidize the monomer and produce hydrogen gas at the cathode.

2. The electrolytic cell of claim 1, wherein the monomer is selected from the group consisting of aniline, pyrrole, thiophene, 3,4-ethylenedioxythiophene and indole, and derivatives thereof, and mixtures thereof.

3. The electrolytic cell of claim 2, wherein the monomer is oxidized at the anode to form a conductive polymer selected from the group consisting of polyaniline, polypyrrole, polythiophene, poly(3,4-ethylenedioxythiophene), and polyindole, and derivatives thereof, and co-polymers thereof.

4. The electrolytic cell of any one of the preceding claims, wherein the acid is a mineral acid or an organic acid, or any mixture thereof.

5. The electrolytic cell of claim 4, wherein the mineral acid is selected from the group consisting of hydrochloric acid (HC1), hydrobromic acid (HBr), nitric acid (HNO3), sulphuric acid (H2SO4), phosphoric acid (H3PO4), boric acid (H3BO3), perchloric acid (HCIO4) and any mixture thereof, or wherein the organic acid is selected from the group consisting of acetic acid (HC2H3O2), carbonic acid (H2CO3), formic acid (H2CO2), lactic acid (CH3CH(OH)COOH), citric acid (HOC(CO2H)(CH2CO2H)2), and any mixture thereof.

6. The electrolytic cell of any one of the preceding claims, wherein the electrolyte solution has a pH of less than 7, or less than about 6, or less than about 5, or less than about 4. 40

7. The electrolytic cell of any one of the preceding claims, wherein the electrolyte solution further comprises a redox mediator capable of oxidizing the monomer.

8. The electrolytic cell of claim 6, wherein the redox mediator is triiodide (I3 ).

9. The electrolytic cell of any one of the preceding claims, wherein the electricity source comprises a photovoltaic cell.

10. The electrolytic cell of claim 9, wherein the photovoltaic cell is a silicon-based cell, a thin- film cell, a multi-junction cell, a perovskite cell, a III-V cell, a dye-sensitized cell, or comprises colloidal quantum dots or organic polymers.

11. The electrolytic cell of claim 9 or claim 10, wherein the electricity source comprises or consists of a series of two or more photovoltaic cells.

12. The electrolytic cell of any one of the preceding claims, wherein the electricity source provides a voltage between about 1 and about 1.8 V.

13. The electrolytic cell of any one of the preceding claims, wherein the cathode comprises a metal, metal oxide, metal alloy, metal phosphide or metal dichalcogenide, each of which comprises at least one of platinum, palladium, rhodium, cobalt, molybdenum, nickel, and manganese; graphite; a carbon nanotube; or a semiconductor material selected from copper (I) oxide (CU2O), p-type silicon and indium phosphide (InP); or any mixture thereof.

14. The electrolytic cell of any one of the preceding claims, wherein the anode comprises fluorine-doped tin oxide; a metal or metal alloy selected from nickel, titanium, platinum, gold and stainless steel; a semiconductor material selected from titanium dioxide (TiCh), zinc oxide (ZnO), tungsten trioxide (WO3), bismuth vanadate (BiVCU), iron(III) oxide / a-hematite (Fe2O3), or gallium nitride (GaN); graphite or a carbon nanotube, or any mixture thereof.

15. The electrolytic cell of any one of claims 1 to 14, wherein the electricity source is the anode and is in fluid contact with the electrolyte.

16. The electrolytic cell of any one of claims 1 to 14, wherein the electricity source is the cathode and is in fluid contact with the electrolyte. 41

17. The electrolytic cell of any one of the preceding claims, wherein the light source is solar light.

18. The electrolytic cell of any one of the preceding claims, further comprising a multimeter capable of monitoring the current and/or the voltage of the electrolytic cell during use.

19. The electrolytic cell of any one of the preceding claims, further comprising a storage device selected from the group consisting of a battery and a hydrogen fuel cell.

20. The electrolytic cell of any one of the preceding claims, further comprising a second light source that is not solar light.

21. The electrolytic cell of any one of the preceding claims, further comprising a stirring system in fluid contact with the electrolyte solution.

22. A process for simultaneous production of a conductive polymer and hydrogen gas, comprising: obtaining an electrolytic cell of any one of the preceding claims; and exposing the electricity source to a light source; wherein the electricity from the device initiates a polymerization reaction at the anode to produce a conductive polymer, and hydrogen gas is produced at the cathode.