EP3695028A1

EP3695028A1 - Nion exchanger fillings through which flow can occur for electrolyte splitting in co2 electrolysis for better spatial distribution of gassing

Info

Publication number: EP3695028A1
Application number: EP18810945.8A
Authority: EP
Inventors: Bernhard Schmid; Günter Schmid; Christian Reller; Dan Taroata
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2017-12-21
Filing date: 2018-11-19
Publication date: 2020-08-19
Also published as: DE102017223521A1; CN111556908A; US20210180196A1; WO2019120812A1

Abstract

The invention relates to an electrolysis cell having a multi-chamber structure, wherein an anion exchanger comprising a first ion exchanger membrane connects to a cathode chamber, wherein a salt bridge chamber connects to said first ion exchanger membrane, said salt bridge chamber comprising a fixed anion exchanger. The invention further relates to an electrolysis system having such an electrolysis cell and to a method for electrolysis of CO₂ using such an electrolysis cell or electrolysis system.

Description

description

Flow-through anion exchanger fillings for electrolyte gaps in CCg electrolysis for better spatial distribution of gas evolution

The present invention relates to an electrolytic cell having a multi-chamber structure, wherein a first ion exchange membrane comprising an anion exchanger adjoins a cathode space, wherein a salt bridge space adjoins this first ion exchange membrane, which comprises a solid Anione exchanger; an electrolysis plant with such an electrolysis cell; and a method for the electrolysis of CO2 using such an electrolytic cell or electro lyseanlage.

The burning of fossil fuels currently covers about 80% of global energy needs. As a result of these incineration processes in 2011, worldwide approx

34,032.7 million tonnes of carbon dioxide (CCg) are emitted into the atmosphere. This release is the easiest way to dispose of even large amounts of CCg (lignite power plants over 50,000 tons per day).

The discussion about the negative effects of the greenhouse gas CO2 on the climate has led to the idea of how to recycle CO2. Considered thermodynamically, CO2 is very low and therefore difficult to reduce to useful products.

In nature, CO2 is converted into carbohydrates by photosynthesis. This temporally and on a molecular level spatially divided into many sub-steps process is very difficult to copy on an industrial scale. The currently more efficient way compared to pure photocatalysis is the electrochemical reduction of CO2. A mixed form is the light-assisted electrolysis or the electrically assisted electrolysis. supported photocatalysis. Both terms are synonymous to use the, depending on the perspective of the beholder.

As with photosynthesis, in this process, with the addition of electrical energy (possibly photo-assisted), which can be obtained from regenerative energy sources such as wind or sun, CO2 is converted into a higher energy product (such as CO, CH ₄ , C ₂ H ₄ , etc.) converted. The amount of energy required for this reduction ideally corresponds to the combustion energy of the fuel and should come from regenerative sources only. However, an overproduction of renewable energies is not continuously available, but currently only at times with strong sunlight and strong wind. However, this will be further strengthened in the near future with the further expansion of renewable energy.

The electrochemical reduction of CO2 on solid-state electrolytes in aqueous electrolyte solutions offers a multitude of product possibilities, for which exemplary Faraday efficiencies on different metal cathodes in Table 1, taken from "Electrochemical CO2 reduction on metal-electodes" by Y. Hori, published in: C. Vayenas, et al. (Eds.) _/ Modern Aspects of Electrochemistry, Springer, New York, 2008, pp. 89-189.

Table 1: Faraday efficiencies in the electrolysis of CO2 on various electrode materials

Currently, the electrification of the chemical industry is discussed. This means that chemical precursors or fuels are preferably to be prepared from C0 ₂ (CO), H ₂ O under supply via schüssiger electrical energy preferably from renewable sources. In the introductory phase of such a technology, the aim is that the economic value of a substance is significantly greater than its calorific value (calorific value).

Electrolysis processes have evolved significantly in recent decades. For example, the PEM water electrolysis could be optimized to high current densities. Large electrolyzers with outputs in the megawatt range are introduced to the market.

In C0 ₂ electrolysis it has been found that coupling the cathode to an anion exchange membrane (AEM) has significant advantages in terms of selectivity, stability and technical feasibility.

Furthermore, it is known that generated by the AEM at the cathode as a byproduct HCO3 can be further transported in the direction of the anode and NEN at one of the cell design dependent location, for example, from anode-side formed Proto, to C0 ₂ can be decomposed. It has been shown that it may be advantageous to use tri-cell cells in which the C0 _{2 is released} separately from the products of the electrodes as this facilitates feedback. Corresponding cell concepts can, for example, the

US 2017037522 A1, DE 102017208610.6, DE

102017211930.6 be removed.

In these cells, the cathode compartment is usually limited by an AEM. As a result, cathodically generated anions such as HCCg, CCg ² , OH can be transported away in the direction of the anode. With respect to the configuration of the anode space and the gap between the anode and cathode space, the sources mentioned vary greatly. Common to them, however, is a region between the AEM, which delimits the cathode space, and the Ano de, which contains a strongly acidic medium or protons he testifies, in which HCO3, CO3 ² are decomposed by protonation to CO2. Furthermore, the charge transport in all these cells can be carried out in sections by different charge carriers. In contrast to other electrochemical structures, the charge carriers are usually not exchanged between the half cells, but destroyed in the additional gap between them.

In US 2017037522 A1 and DE 102017211930.6, the central gap contains only strongly acidic media. The release of the CO2 is therefore usually carried out directly on the surface of the AEM, wherein in US2017037522A1 the medium of the gap is fixed, while it is liquid in DE 102017211930.6. The surface of the AEM can be heavily loaded with gas bubbles, which can lead to a partial isolation of the membrane and thus to higher electrical losses in the cell. A direct contact of strongly acidic solid media with the AEM should also be avoided since the solid media can not escape the CO2 released at this pH limit.

In DE 102017208610.6 the gap contains a neutral to weakly basic electrolyte, which usually contains carbonates. The release of CO2 therefore usually takes place on the upper surface of the second separator membrane, which may also be prob lematic. In addition, it has been shown that the use of fertil salts, in particular with metal cations, in Elek rolytespalten may be associated with disadvantages.

At present, no solutions to the problem described be known. Its extent, as described in DE 102017208610.6 ben, can be reduced by increasing the system pressure. However, an excessive pressure increase is not desirable due to the increased solubility of gases in water.

There is thus a need for an improved electrolyte cell or an improved electrolysis system which can effectively avoid the formation of gas bubbles on a membrane in a multi-chamber system.

The inventors have found that with an additional electrolyzer component in particular the cell voltage, the operational stability and the energy efficiency can be improved. In this case, this component is preferably inte grated so that in the resulting entire cell neither salt encrustations of the electrodes nor CO2 development in the anode space are possible. The present invention represents a significant improvement of previously disclosed cell concepts.

This is achieved in particular by filling a salt bridge space in an electrolysis cell with a solid anion exchanger which comprises at least in the vicinity of the cathode / AEM an, for example bicarbonate, carbonate and / or hydroxide conductive, for example, strongly basic Anionenaus exchanger. The anion exchanger leads to the fact that a gas evolution, for example the CO ₂ evolution in CO ₂ electrolysis, can be distributed in the salt bridge space into the volume and does not take place only at the AEM salt bridge space interface.

In the following, the terms anion exchanger and anion transporter are used interchangeably. The transport function is characterized in that the anion exchange / anion cations that compensate for the charge of the anions. The anion per se is, according to certain embodiments, only so easily bound that a dynamic exchange is made possible, thus providing a transport path for the anion in the electrolyte. At the same time, the cation is immobilized on the polymer back wheel of the anion exchange material, so that it itself can not participate in charge transport processes.

In a first aspect, the present invention relates to an electrolytic cell comprising

a cathode compartment comprising a cathode;

a first ion exchange membrane containing an anion exchanger and adjacent to the cathode compartment, the cathode contacting the first ion exchange membrane;

an anode compartment comprising an anode; and

a first separator adjacent to the anode compartment;

further comprising a salt bridge space, wherein the salt bridge space between the first ion exchange membrane and the first separator is arranged, wherein the salt bridge space comprises a solid anion exchanger which is at least partially in contact with the first ion exchange membrane.

Further disclosed is an electrolysis plant comprising an electrolysis cell according to the invention.

In addition, the present invention is directed to a process for the electrolysis of CCg, wherein an electrolytic cell or an electrolysis plant according to the invention is used, wherein CCg is reduced at the cathode and at the cathode resulting bicarbonate and / or Carbo nat through the first ion exchange membrane to an electric lyten in the salt bridge space, wherein the bicarbonate and / or carbonate also by the solid anion exchanger transported in the salt bridge space away from the first ion exchange membrane.

Yet another aspect of the present invention relates to the use of an electrolysis cell according to the invention or an electrolysis plant according to the invention for the electrolysis of CO2 and / or CO.

Further aspects of the present invention are the dependent claims and the detailed description to entneh men.

Description of the figures

The accompanying drawings are intended to illustrate embodiments of the present invention and to provide further understanding thereof. In the context of the description, they serve to explain concepts and principles of the invention. Other embodiments and many of the genann th advantages will become apparent with regard to the drawings.

The elements of the drawings are not necessarily to measure scale shown to each other. The same, functionally identical and same-acting elements, features and components are provided in the figures of the drawings, unless otherwise stated, each provided with the same reference numerals.

Figures 1 to 9 show schematically possible embodiments of an electrolytic cell according to the invention.

FIG. 10 schematically shows, by way of example, an electrolysis plant according to the invention.

Detailed description of the invention

definitions

Unless defined otherwise, technical and scientific terms used herein have the same meaning, as commonly understood by one of ordinary skill in the art.

Quantities in the context of the present invention are based on wt. %, unless otherwise stated or obvious from the context. In the gas diffusion electrode according to the invention, the weights complement each other. % Shares to 100 wt. %.

In the context of the present invention, what is meant to be hydrophobic is water-repellent. Hydrophobic pores and / or channels according to the invention are therefore those which repel water. In particular, hydrophobic properties are associated according to the invention with substances or molecules with nonpolar groups.

In contrast, the ability to interact with water and other polar substances is understood to be hydrophilic.

Gas diffusion electrodes (GDE) in general are electrodes in which liquid, solid and gaseous phases are present, and where, in particular, a conductive catalyst catalyzes an electrochemical reaction between the liquid and the gaseous phase ka.

The embodiment can be of different nature, for example, as a porous "solid catalyst" with possibly auxiliary layers for adjusting the hydrophobicity, in which case for example a membrane-GDE composite, eg AEM-GDE composite, can be produced, as a conductive porous support, on which a catalyst can be applied in a thin layer, in which case again a membrane-GDE composite, eg AEM-GDE composite, can be produced, or as a composite porous catalyst, optionally with an additive directly on a membrane, eg AEM, can be applied and then in combination can form a catalyst coated membrane (CCM). The normal pressure is 101325 Pa 1, 01325 bar.

Electro-osmosis:

Electro-osmosis is an electrodynamic phenomenon in which a force towards the cathode acts on particles in solution with a positive zeta potential and a force acts on the anode on all particles with a negative zeta potential. If conversion takes place at the electrodes, i. flows a galvanic current, so it comes also to a stream of particles with positive zeta potential for Ka method, regardless of whether the species is involved in the implementation or not. The same applies to a negative zeta potential and the anode. If the cathode is porous, the medium is also pumped through the electrode. It is also known as an electro-osmotic pump.

The material flows caused by electro-osmosis can also flow in opposite directions to concentration gradients. Diffusion-related currents that balance the concentration gradients can thereby be overcompensated.

a cathode compartment comprising a cathode;

an anode compartment comprising an anode; and

a first separator adjacent to the anode compartment;

further comprising a salt bridge space, wherein the salt bridge space between the first ion exchange membrane and the first separator is arranged, wherein the salt bridge space comprises a solid anion exchanger which is at least partially in contact with the first ion exchange membrane. The salt bridge space is not particularly limited insofar as it corresponds to the first ion exchange membrane at least partially, in particular mechanically and / or ionically, to close, so that the solid anion exchanger in this can be at least partially in contact with the first ion exchange membrane. According to certain embodiments, the solid anion exchanger is in contact with the first ion exchange membrane at least substantially in a region in which the cathode contacts the first ion exchange membrane on an opposite side of this membrane, or in an area that is larger. This allows a good Wei terleitung of anions, which are generated in the cathode and passed through the first ion exchange membrane, si chergestellt. The term "with the first Ionenaustau shear membrane in contact" does not exclude that the contact is not full-surface, but according to certain embodiments such that a flow of fluids, so liquids and / or gases through the solid anion exchanger possible is.

The term salt bridge space is hereby used with regard to its function to act as a "bridge" between anode arrangement and cathode arrangement and in this case to have cations and anions, which in the present case do not have to form salts, since in the present case at least one ion exchanger is present in the salt bridge space. However, since this term is not common, the space is referred to as salt bridge space according to the invention, even if there is no salt in the classical sense.

The dimensions of the salt bridge space are also not particularly limited, and it may for example be formed as a space or gap, for example, between the first ion exchange membrane and the first separator, which are arranged, for example, parallel zueinan of. The salt bridge space does not necessarily have to be in contact with the first separator, which adjoins the anode compartment, ie more than three chambers may be present in an electrolysis cell according to the invention. Thus, the term "interposed between the first ion exchange membrane and the first separator" means that the salt bridge space may be located anywhere between the first ion exchange membrane and the first separator, in so far as it comprises a solid anion exchanger which at least partially communicates with the first In this respect, the salt bridge space adjoins the first ion exchange membrane, which does not exclude, however, that a second separator or further separators and / or further cell spaces are present in addition to the first separator In this respect, the electrolysis cell according to the invention can be constructed, for example, as a multi-chamber cell, eg a three-chamber cell, as described in US 2017037522 A1, DE102017208610.6, and DE102017211930.6, and to which reference is made with respect to such cells is taken. Thus, for example, there may be a three-chamber cell in which there are three chambers (I, II, III). With the salt bridge space can thus be the electrolytic contact between the cathode compartment and anode compartment acts and / or be facilitated.

The cathode compartment, the anode compartment and salt bridge compartment are not particularly limited in the electrolytic cell according to the invention in terms of shape, material, dimensions, etc., in so far as they can accommodate the cathode, the anode and the first Ionenaustau shear membrane and the first separator. The three spaces are formed in the electrolysis cell according to the invention, in which case they can be correspondingly separated, for example, by the first ion exchange membrane and the first separator, for example with the first separator between the salt bridge space and the anode space. Depending on the electrolysis to be carried out, corresponding supply and discharge devices for starting materials and products, for example in the form of liquid, gas, solution, suspension, etc., may be provided for the individual spaces, and these may possibly also be recycled in each case. Again, there is no limitation, and the individual rooms can be flowed through in parallel streams or in countercurrent. For example, in an electrolysis of CO2 - which may still contain CO, so for example, at least 20 vol.% CO2 - this solution to the cathode in solu tion, as gas, etc. are supplied - for example, in countercurrent to an electrolyte flow in the salt bridge space at a three-chamber construction. There is no restriction.

Corresponding feeding possibilities also exist in the anode room and are also explained in more detail below. The respective supply can be provided both continuously and discontinuously, for example pulsed, etc., for which pumps, valves, etc. may be provided in a fiction, contemporary electrolysis - which will also be discussed below, as well as cooling and / or Heating means to catalyze corresponding desired reactions at the anode and / or cathode can.

The materials of the respective rooms or the Elektrolysezel le and / or the other components of the electrolysis system can also be suitably adapted to desired reactions, reactants, products, electrolytes, etc. here. In addition, of course, at least one power source per electrolytic cell is included. Also before further device parts, which are in electrolysis cells or electrolysis plants _V , can be provided in the electrolytic seanlage invention or the electrolytic cell according to the invention. According to certain embodiments, a stack is constructed from these individual cells, which comprises 2 to 1000, preferably 2 to 200 cells, and whose operating voltage is preferably in the range of 3 to 1500 V, particularly preferably 200 to 600 V. According to certain embodiments, a gas formed in the salt bridge, which corresponds for example to the educt gas, for example CO ₂ , which may also, if necessary, traces of H ₂ and / or CO ent hold back to the cathode space, where for in a inventive Electrolysis an ent speaking return device can be provided.

The cathode according to the invention is not particularly limited and may be adapted to a desired half-reaction, for example with respect to the reaction products, insofar as it contacts the first ion exchange membrane directly, that is in direct contact with the first ion exchange membrane at at least one location, preferably wherein the cathode substantially surface is in direct contact with the first Ionenaustauschermemb ran. Thus, at least in one region, the cathode directly adjoins the first ion exchange membrane. A cathode for the reduction of CO ₂ and optionally CO may, for example, a metal such as Cu, Ag, Au, Zn, Pb, Sn,

Bi, Pt, Pd, Ir, Os, Fe, Ni, Co, W, Mo, etc., or mixtures and / or alloys thereof, preferably Cu, Ag, Au, Zn, Pb, Sn, or mixtures and / or alloys thereof, and / or a salt thereof, wherein suitable materials can be adapted to a desired product. The catalyst can be chosen with depending on the desired product. In the case of the reduction of CO ₂ to CO, for example, the catalyst is preferably based on Ag, Au, Zn and / or their compounds such as Ag ₂ 0, AgO, AU ₂ O, AU ₂ O ₃ , ZnO. For the preparation of hydrocarbons Cu or Cu-containing compounds such as CU ₂ O, CuO and / or copper-containing mixed oxides with other metals, etc., are preferred. For a production of formic acid, for example, catalysts based on Pb, Sn and / or Cu, in particular Pb, Sn, are possible. Since the formation of hydrogen at high current densities can be completely suppressed by anion transport according to certain embodiments, catalysts for C0 ₂ reduction can also be used, those who do not have a high overvoltage to hydrogen, eg reduction catalysts such as Pt, Pd, Ir, Os or carbonyl-forming metals such as Fe, Ni, Co, W, Mo. Thus, the mode of operation described in connection with cell design opens up new avenues in CCg reduction chemistry, which do not depend on hydrogen overvoltage.

The cathode is the electrode at which the reductive half-reaction takes place. It may be one or more parts and be ausgebil det, for example, as a gas diffusion electrode, porous electrode or directly with the AEM in the composite, etc.

The following embodiments are hereby possible, for example:

Gas diffusion electrode or porous bonded Kataly satorstruktur, which according to certain embodiments by means of a suitable ionomer, for example egg nes anionic ionomer, with the first Ionenaustau shear, for example, an anion exchange membrane (AEM), e.g. can be glued ion-conducting and / or mechanically nich;

Gas diffusion electrode or porous bonded cata- sator structure, which may be partially pressed according to certain embodiments in the first ion exchange membrane, for example, an AEM;

porous, conductive, catalytically inactive structure, eg carbon-paper-GDL or carbon-paper-GDL (gas diffusion layer, gas diffusion layer), carbon cloth-GDL or carbon-cloth GDL, and / or poly mergebundener film granular glassy carbon impregnated with the catalyst of the cathode and optionally an ionomer that schermembran the connection to the first Ionenaustau, for example, an AEM, impregnated, wherein the electrode then mechanically to the first ion exchange membrane, such as an AEM, pressed or before can be pressed with the first ion exchange membrane, for example an AEM, to form a composite; Particulate catalyst, which by means of a suitable ionomer on a suitable carrier, for example a porous conductive support, is applied and, according to certain embodiments, can abut the first ion exchange membrane, for example an AEM;

particulate catalyst, in which the first ion exchange membrane, for example, an AEM, is pressed or is coated on this and is correspondingly conductively connected, for example, this structure then, for example, as a so-called CCM (catalyst-Caoted membrane, catalyst-coated membrane ) can then be pressed onto a conductive, porous electrode, wherein a catalytic activity of this electrode is basically not required and, for example, carbon-based GDI / s or lattices, for example made of titanium, can be used, wherein it is not excluded that this electrode ionomers contains and / or contains the active catalyst or be it in large parts be;

unfastened sheet, e.g. a mesh or expanded metal, for example, consisting of or comprising a catalyst or coated with the sem and according to certain embodiments forms on the first ion exchange membrane, for example, an AEM, is applied;

polymer-bound unsupported catalyst structure from parti cular catalyst, which contains an ionomer, the tion to the first ion exchange membrane, example, an AEM, contains, or was subsequently impregnated therewith, wherein the electrode me then mechanically on the first ion exchange membrane, for example a AEM, pressed or previously compressed with the first ion exchange membrane, for example an AEM, to form a composite; porous, conductive carrier impregnated with a suitable catalyst and optionally an ionomer and, according to certain embodiments, at the first Ion exchange membrane, for example an AEM, is present;

non-ionic gas diffusion electrode which has been subsequently impregnated with a suitable ionomer, for example an anionic conductive ionomer, and according to certain embodiments is applied to the first ion exchange membrane, for example an AEM, or is attached thereto, e.g. via an ionomer.

Also, various combinations of the above-described Elektoden structures are possible as a cathode.

The corresponding cathodes may in this case also contain materials customary in cathodes, such as binders, ionomers, for example anionic ionomers, fillers, hydrophilic additives, etc., which are not particularly limited. Thus, according to certain embodiments, besides the catalyst, the cathode may comprise at least one ionomer, for example an anionic or ion transporting ionomer (e.g., anion exchange resin, anion transport resin), e.g. various functional groups for ion exchange, which may be the same or different, for example, tertiary amine groups, alkylammonium groups and / or phosphonium groups), e.g. conductive, support material (e.g., a metal such as titanium), and / or at least one non-metal such as carbon, Si, boron nitride (BN), boron

doped diamond, etc., and / or at least one conductive oxide such as indium tin oxide (ITO), aluminum zinc oxide (AZO) or fluorinated tin oxide (FTO) - for example, as used to prepare photoelectrodes, and / or at least one polymer based on Polyacetylene, polyethoxythiophene, polyaniline or polypyrrole, such as in polymer-based electrodes; non-conductive supports such as polymer networks are possible, for example, with sufficient conductivity of the catalyst layer), binders (eg hydrophilic and / or hydrophobic polymers, eg organic binders, for example selected from PTFE (polytetrafluoroethylene), PVDF (Polyvinyliendifluorid), PFA (perfluoroalkoxy polymers), FEP (fluorinated ethylene-propylene copolymers), PFSA (perfluoro sulfonic acid polymers), and mixtures thereof, in particular PTFE), conductive fillers (eg carbon), non-conductive fillers (eg Glass) and / or hydrophilic additives (eg Al 2 O 3, MgCg, hydrophilic materials such as polysulfones, eg polyphenylsulfones, polyimides, polybenzoxazoles or

Polyether ketones or generally in the electrolyte electrochemically stable polymers, polymerized "ionic liquids th", and / or organic conductors such as PEDOT: PSS or PANI (champhersulfonsäuredortiertes polyaniline) included, which are not particularly limited.

The cathode, in particular in the form of a gas diffusion electrode, e.g. bonded to the first ion exchange membrane, or contained in the form of a CCM, according to certain embodiments, contains ionically conductive components, in particular an anionic conductive component.

Other cathode shapes are also possible, for example cathode constructions as described in US 20160251755 A1 and US 9481939.

Also, the anode according to the invention is not particularly limited and may be adapted to a desired half-reaction, for example, with respect to the reaction products. At the anode, which is electrically verbun with the cathode by means of a power source for the provision of the voltage for the electrolysis, takes place in the anode compartment, the oxidation of a substance. Moreover, the material of the anode is not particularly limited and depends primarily on the desired reaction. Exemplary anode materials include platinum alloys, palladium and glassy carbon, iron, nickel, etc. Other anode materials are also conductive oxides such as doped TiO 2, indium tin oxide (ITO), fluorine doped tin oxide (FTO), aluminum doped Zinc oxide (AZO), iridium oxide, etc. These catalytically active compounds can only be superficially applied in thin film technology, for example, on a titanium and / or carbon support. The anode catalyst is not particularly limited. As cata- capacitor for 0 ₂ - or Cl 2 ~ generation, for example, IrO _x (1.5 <x <2) or RuCg are used. These may also be present as mixed oxide with other metals, eg TiCg, and / or be supported on a conductive material such as C (in the form of carbon black, activated carbon, graphite, etc.). Alternatively, it is also possible to use catalysts based on Fe-Ni or Co-Ni for O ₂ generation. For this purpose, for example, the un described construction with bipolar membrane or bipolar membrane is suitable.

The anode is the electrode at which the oxidative half reaction takes place. It can also be designed as a gas diffusion electrode, porous electrode or solid electrode or solid electrode, etc.

The following embodiments are possible:

Gas diffusion electrode or porous bonded Kataly satorstruktur, which according to certain embodiments by means of a suitable ionomer, for example egg nes cationic ionomer, with the first separator, for example a cation exchange membrane (CEM) or a diaphragm, e.g. can be glued ion-conducting and / or me chanic;

Gas diffusion electrode or porous bonded cata- capacitor structure which may be partially pressed into the first separator, for example a CEM or a diaphragm, according to certain embodiments;

particulate catalyst applied by means of a suitable ionomer to a suitable support, for example a porous conductive support, and according to certain embodiments may abut the first separator, for example a CEM or a slide;

Particulate catalyst, the gate in the first Separa, for example, a CEM or a diaphragm, is pressed and, for example, lei tend connected accordingly;

unfastened sheet, e.g. a mesh or expanded metal, for example, consisting of or comprising a catalyst or coated with the sem and according to certain embodiments forms on the first separator, for example a CEM or a diaphragm, is applied;

solid electrode, in which case there may also be a gap between the first separator, for example a CEM or a diaphragm, and the anode;

porous, conductive carrier which is impregnated with a suitable catalyst and optionally an ionomer and according to certain embodiments on the first Se parator, for example a CEM or a Dia phragma, is applied;

non-ionic gas diffusion electrode which has subsequently been impregnated with a suitable ionomer, for example a cation-conductive ionomer, and, according to certain embodiments, is applied to the first separator, for example a CEM or a diaphragm;

any variants of the discussed embodiments, the electrode e.g. contains an anodically stable anionic conductive material and is located directly on the anionic conductive layer of a bipolar membrane.

Again, various combinations of different anode structures are possible.

The corresponding anodes can also contain materials customary in anodes such as binders, ionomers, for example cation-conducting ionomers, for example containing sulfonic acid and / or phosphonic acid groups, fillers, hydrophilic additives, etc., which are not particularly limited for example, also described above with respect to the cathode.

According to certain embodiments, the cathode and / or the anode is a gas diffusion electrode, a porous bound catalyst structure, as a particulate catalyst on a support, as a coating of a particulate catalyst on the first and / or second ion exchange membrane, as a porous conductive support into which a catalyst is impregnated, and / or forms out as a non-closed sheet. According to certain embodiments, the cathode as a gas diffusion electrode, as a porous bound catalyst structure, as a particulate catalyst on a support, as a coating of a particulate catalyst on the first and / or second ion exchange membrane, as a porous leitfä Higer carrier in which a catalyst is impregnated

and / or formed as a non-closed sheet containing (r / s) an anion exchange material and / or anions transport material. According to certain embodiments, the anode is a gas diffusion electrode, a porous bonded catalyst structure, a particulate catalyst on a support, as a coating of a particulate catalyst on the first and / or second ion exchange membrane, as a porous conductive support into which a catalyst is impregnated. and / or formed as a non-closed sheet, which (r / s) holds a cation exchange material ent and / or coupled to a bipolar membrane and / or ge is bound.

According to certain embodiments, the anode and / or the cathode are contacted with a conductive structure on the side facing away from the salt bridge space. The conductive structure is not particularly limited here. The anode and / or the cathode are therefore contacted in accordance with certain embodiments of the salt bridge opposite side by leitfähi ge structures. These are not particularly limited. These may be, for example, coal flows, Metal foams, metal knits, expanded metals, Grafitstruktu ren or metal structures act.

In an electrolysis cell according to the invention as well as in the method according to the invention, the electrodes mentioned above by way of example can be combined with one another as desired.

In addition, electrolytes may also be present in the anode space and / or cathodes, which are also referred to as anolyte or catholyte, but it is not excluded according to the invention that no electrolytes are present in the two spaces and correspondingly, for example, only Ga se for reaction in These are supplied, for example, only CO ₂ , if necessary, as a mixture with, for example, CO and / or H ₂ O, which may also be liquid, for example as an aerosol, but before given to gaseous H ₂ O to the cathode and / or water or HCl to the anode. According to certain embodiments, an anolyte is present which may differ from or correspond to an electrolyte of the salt bridge space, for example with respect to contained solvents, acids, etc.

A catholyte is in this case the electrolyte flow to the cathode or at the cathode and is used according to certain embodiments forms the supply of the cathode with substrate or reactant.

The following embodiments are possible, for example. The catholyte can be used, for example, as a solution of the substrate (CO ₂₎ in a liquid carrier phase (eg water) and / or as a mixture of the substrate with other gases (eg CO + CO _2, water vapor + CO _2, N ₂ and / or also) certain proportions of O ₂ , SO ₂ , SO _3, etc.) are present. Also can be present by a recirculation zurückge led gases such as CO and / or H ₂ . The substrate can also be in the form of a pure phase, for example CO ₂ . If uncharged liquid products are formed during the reaction, they can be washed out by the catholyte and can then optionally be separated off as required. An anolyte is an electrolyte stream around the anode or at the anode and, according to certain embodiments, serves to supply the anode with substrate or starting material and, if appropriate, from the anode products. The following Ausführungsfor men are possible, for example. The anolyte can as a solution of the substrate (eg hydrochloric acid = HCl _aq) in a liquid carrier phase (eg water), optionally with conductive salts, which are not limited - especially when using a bipolar membrane as the first separator membrane, the anolyte here as well may be basic and may also contain cations, as described below, or as a mixture of the substrate with other gases (eg hydrochloric acid = HCl _g + H ₂ O, SO ₂ , etc.) are present. However, as with the catholyte, the substrate can also be present as a pure phase, for example in the form of hydrogen chloride gas = HCl _g .

According to certain embodiments, the anolyte is an aqueous electrolyte, wherein the corresponding anolyte may optionally be added to the anolyte, which are reacted at the anode. The educt addition is not particularly limited here.

Likewise, the educt addition in the supply to the cathode space is not limited. For example, CO ₂ may be added to water outside the cathode compartment, or may also be added through a gas diffusion electrode, or may be supplied only as a gas to the cathode compartment. Corresponding considerations are possible analogously for the anode compartment, depending on the reactant used, for example water, HCl, NaCl, KCl, etc., and the desired product.

The first ion exchange membrane which contains an anion exchanger and / or anion transporter or an anion transport material and which adjoins the cathode compartment is not particularly limited in the present invention. It separates in the electrolytic cell according to the invention as well as in the inventions to the invention process, the cathode of the salt bridge space, so that from the direction of the cathode space in the direction of the electrolyte, the order of cathode / first ion exchange membrane / salt bridge space results. It contains in particular certain embodiments of an anion exchanger or consists of this, which is in the form of an acid-anion salt in the currentless state, preferably according to an acid which is present in the salt bridge space, and which more preferably passes from a minimum current density in the hydrogencarbonate / carbonate form , According to certain embodiments, the first ion exchange membrane is an anion exchange membrane and / or anion transporter membrane. According to certain embodiments, the first ion exchange membrane may have a hydrophobic layer, for example on the cathode side for better gas contacting. Preferably, the anion exchange membrane and / or Anionentrans portermembran also acts as cation (albeit in traces, for example), in particular proton, blocker. Specifically, an anion exchanger and / or anion transporter with tightly bound Ka tions can represent a blockade for mobile cations by Coulombabstoßung what a Salzausschei tion, in particular within the cathode, in addition can counteract entge.

In particular, in a membrane electrode assembly (MEA), the accumulation of electrolyte cations in the area of the interface is usually due to the electroosmosis.

A concentration gradient can not be easily degraded on the electrode side, since a catalyst-based cathode, which is designed as set out above, e.g. ei ne gas diffusion electrode or a CCM, optionally only has a very poor Anionenleitfähigkeit, depending on the anion and a selected electrolyte. By the integration of anion-conducting components, the anion conductivity can be significantly improved here.

To improve the operational stability, ion transport agents, in particular anion transport resins, can be used as binder material or additive in the electrode itself

and / or in an anion exchanger layer, which rests against the cathode in order, for example, to quickly dissipate or partly buffer off OH ions which are formed, so that the action with CO ₂ and the associated formation of hydrogencarbonates and / or carbonates can be reduced or the anion transport resins HCCg or CCg ^2- direct self.

In principle, an anion transport can take place by Anionenaus exchanger. Furthermore, especially an integrated anion exchanger again provides a blockage for cations, e.g. Metallkationpuren, what a Salzaus divorce and contamination of the electrode can additionally counteract entge. In the case of protons, for example, the formation of hydrogen can be suppressed.

The first ion exchange membrane may thus contain, for example, an anion exchanger and / or anion transporter in the form of an anion exchanger and / or transporter layer, in which case further layers such as hydrophobicizing

Layers to improve contact with a gas, e.g.

CO ₂ , may be included. According to certain embodiments, the first ion exchange membrane is an anion exchange membrane and / or anion transporter membrane, ie, for example, an ion-conducting membrane (or also a membrane having an anion exchange layer and / or anion transport layer) with positively charged functionalizations, which is not particularly limited , A preferred charge transport takes place in the Anionenaus exchanger layer and / or Anionentransporterschicht or an anion exchange membrane and / or Anionentransportermembran by anions. In particular, the first ion exchange membrane and / or an anion exchanger layer and / or anion transport layer or an anion exchange membrane and / or anion transport membrane serves to provide an anion transport along fixed fixed positive charges. In particular, the penetration of an electrolyte, for example proton-containing electrolyte, into the cathode promoted by electro-osmotic forces can be reduced or completely avoided. The ion exchanger contained in the membrane may, according to certain embodiments, be in particular in operation in the carbonate / hydrogen carbonate form and thereby suppress the passage of protons through the membrane to the cathode.

A suitable first ion exchange membrane, for example anion exchange membrane and / or anion transporter membrane, exhibits, according to certain embodiments, a good wettability by water and / or acids, in particular aqueous acids, a high ionic conductivity, and / or a tolerance of the functional groups contained therein to high pH values. Values, in particular shows no Hoffmann elimination. An exemplary AEM according to the present invention is the A201-CE membrane marketed by Tokuyama, the "Sustainion" marketed by Dioxide Materials, or an anion exchange membrane sold by Fumatech, such as Fumase FAS-PET or Fumasep FAD-PET.

In addition, the first separator is not particularly limited.

According to certain embodiments, the first separator, for example according to certain embodiments, seen from the anode side adjacent to the salt bridge space, selected from an ion exchange membrane containing a cation exchanger, a bipolar membrane, wherein in the bi-polar membrane preferably the cation conductive layer toward the cathode is oriented and the anions conductive layer towards the anode, and a diaphragm. According to certain embodiments, the first separator is a cation exchange membrane, a bipolar membrane or a diaphragm.

A suitable first separator, for example a cation exchange membrane or a bipolar membrane, contains, for example, a cation exchanger which can be in contact with the salt bridge space. It may, for example, contain a cation exchanger in the form of a cation exchanger layer, in which case further layers, such as hydrophobicizing layers, may be contained. It may also be designed as a bipolar membrane or as a cation exchange membrane (CEM). The cation exchange membrane or cation exchange layer is, for example, an ion-conductive membrane or ion-conductive layer with negatively charged functionalities. Exemplary charge transport into the salt bridge space takes place in such a first separator by means of cations. For example, commercially available Nafion® membranes are suitable as CEM, or even the Fumatech-driven Fumapem-F membranes, the Asahi Kasei-marketed Aciplex, or the Flemion membranes marketed by AGC.

In principle, however, it is also possible to use other polymer membranes modified with strongly acidic groups (groups such as sulfonic acid, phosphonic acid). According to certain embodiments, the first separator prevents the passage of anions, in particular HCO3-, into the anode compartment.

In addition, in the electrolysis cell according to the invention, as well as in the method according to the invention, the first separator may be formed as a diaphragm, whereby the cell less complex and cheaper can be designed. According to certain embodiments, the diaphragm essentially separates the anode space and the salt bridge space, for example more than 70%, 80% or 90%, based on the interface between anode space and salt bridge space, or separates the anode space and the salt bridge space, that is to say 100%, based on the boundary surface between anode space and salt bridge space. The same applies to other first separators. Particularly preferred are embodiments which effect gas separation, e.g. the CO2 in the salt bridge space and the O2 in the anode space.

The diaphragm is not particularly limited in this case and may be based, for example, on a ceramic (e.g., ZrO 2 or Zr 3 (PO 4) 3) and / or a swellable functionalized polymer, e.g. PTFE, be. Also, binders (e.g., hydrophilic and / or hydrophobic polymers, e.g., organic binders, e.g., selected from PTFE (polytetrafluoroethylene), PVDF

(Polyvinylidene difluoride), PFA (perfluoroalkoxy polymers), FEP (fluorinated ethylene-propylene copolymers), PFSA

(Perfluorosulfonic acid polymers), and mixtures thereof, in particular special PTFE), conductive fillers (eg carbon), non-conductive fillers (eg glass) and / or hydrophilic additives (eg AI2O3, MgCg, hydrophilic materials like

Polysulfones, e.g. Polyphenylsulfones (PPSU), polyimides,

Polybenzoxazoles or polyether ketones or in general Elekt rolyten electrochemically stable polymers may be present.

According to certain embodiments, the diaphragm is porous and / or hydrophilic. Since it is not ion-conductive itself, it should preferably be able to swell in an electrolyte, such as an acid. Furthermore, it is a physical barrier to gases and can not be penetrated by gas bubbles. For example, it is a porous polymer structure wherein the base polymer is hydrophilic (eg PPSU). In contrast to the CEM or bipolar membrane, the polymer does not contain charged functionalities. Furthermore, the diaphragm may further preferably comprise hydrophilic structuring components such as metal oxides (eg, ZrO ₂ and / or other materials such as particles over the top of which flies) or ceramics as set forth above.

A suitable first separator, for example, a cation exchange membrane, a bipolar membrane and / or a diaphragma, exhibits, according to certain embodiments, good wettability by water and / or acids, high ionic conductivity, stability to reactive species generated at the anode can be (for example ge give perfluorinated polymers), and / or stability in the required pH regimes, for example, to an acid in the salt bridge space.

According to certain embodiments, the first ion exchange membrane and / or the first separator are hydrophobic, in particular so that they form a CCM with the electrodes, at least on the side facing the electrodes, so that the starting materials of the electrodes are present in gaseous form. According to certain embodiments, the anode and / or cathode are at least partially hydrophilic. According to certain embodiments, the first ion exchange membrane and / or the first separator are wettable with water. In order to ensure a good ionic conductivity of ionomers, it is preferable to swell with water. The experiment has shown that poorly wettable membranes or separators can lead to a significant deterioration of the ionic bonding of the electrodes.

The presence of water is also advantageous for some of the electrochemical reactions on the catalyst electrodes. + C0 ₃ ^2-

Therefore, according to certain embodiments, the anode and / or cathode also have sufficient hydrophilicity. Possibly. This can be adjusted by hydrophilic additives such as Ti0 ₂ , A1 ₂ 0 ₃ , or other electrochemically inert metal oxides, etc.

In particular, according to certain embodiments, at least one of the following first separators is used:

A diaphragm is preferably used when the salt bridge (the electrolyte in the salt bridge space) and the anolyte ne identical, preferably inert, acid or consist of this, in which case the diaphragm serves to keep gases separated so that carbon dioxide is not in the anode space crossing, and / or if at the anode 0 _{2 is} produ ed, in particular to save costs.

A cation exchange membrane or a membrane with a cation exchange layer are used in particular when an electrolyte in the salt bridge space - also referred to in the context of the invention as "salt bridge", and the anolyte are not identical, and / or in particular when the anolyte HCl, HBr and / or HI contains, and / or if a Chlorproduk tion at the anode takes place.As the cation exchange membrane, the passage of anions from the anolyte into the salt bridge prevented and in contrast to the diaphragm has no open Po rosity, the anode can be designed freely. In principle, in such an embodiment, it is preferable for the anode reaction to release no mobile cations except protons that can pass into the salt bridge through the CEM.

A bipolar membrane or bipolar membrane, wherein preferably an anion exchanger layer and / or Anionentransporterschicht the bipolar membrane to the anode space is directed towards ge and a cation exchange layer and / or Kat ionentransporterschicht the bipolar membrane directed to the salt bridge back space is used in particular if the salt bridge, so the electrolyte in the salt bridge space, and the anolyte are not identical, and / or the anolyte contains particular special bases and or salts, and / or when using aqueous electrolytes. Particularly in the case of the use of bipolar membranes as the first separator, the anode compartment can be designed independently of the salt bridge and the cathode compartment, which allows a multiplicity of anode reactions with desired products, and in particular when using bases, cheaper anodes or anode catalysts, for example nickel, can also be used or iron based anode catalysts for oxygen evolution.

A bipolar membrane may, for example, be designed as a sandwich of a CEM and an AEM. In this case, but usually not two superimposed membranes before present, but it is a membrane with at least two layers. These membranes are almost impassable for both anions and cations. The conductivity of a bipolar membrane is therefore not based on the ability to transport ions. Instead, ion transport usually occurs by acid-base dissociation of water in the middle of the membrane. As a result, two opposite gela dene charge carriers are generated, which are ported by the E-field abtrans. Since the conductivity of the bipolar membrane is based on the separation of charges in the membrane, however, is usually expected with a higher voltage drop.

The advantage of such a structure lies in the decoupling of the electrolyte circuits, since, as already mentioned, the Bipo lar membrane for all ions is almost impermeable.

As a result, it is also possible for a basic anode reaction to be realized on a construction which does not require constant tracking and removal of salts or anode products. This is otherwise only possible when using anolyte based on acids with electrochemically inactive anions such as H ₂ SO ₄ . When using a bipolar membrane and Hydro xid electrolytes such as KOH or NaOH can be used as the anolyte who the. High pH values thermodynamically promote water oxidation and allow the use of much cheaper anode catalysts, for example based on iron-nickel, which would not be stable in acidic or neutral form.

Thus, for the purposes of the invention, when using a bipolar membrane as the first separator membrane, the use of bases, e.g. a hydroxide base, as anolyte when an acid is used in the salt bridge.

It is not excluded according to the invention that further membranes and / or diaphragms are provided in addition to the first ion exchange membrane and the first separator.

According to certain embodiments, the anode contacts the first separator, as already described above by way of example. As a result, a good connection to the salt bridge space is possible, please include. In addition, no charge transport through the anolyte is necessary in this case and the charge transport path is shortened. Also electrical shading effects by supporting structures between the anode and the first separator can be bypassed so. The solid anion exchanger, which is at least partially in contact with the first ion exchange membrane and is included in the salt bridge space, according to the invention is not limited FITS, if it is present as a solid - so not in solution, can exchange anions, and at least partially with the first ion exchange membrane in Contact is. Preferably, the solid anion exchanger is hydrophilic.

As already explained above, it is preferred that the solid anion exchanger, at least in the region of the cathode on the opposite side of the first ion exchange membrane, is substantially in contact therewith, that is to say more than 50% of the area of the first ion exchange membrane, preferably more than 60 %, more preferably more than 70%, in particular more than 80%, are in contact with the solid anion exchanger - that is, touching it, based on the area of the first ion exchange membrane which is in contact with the cathode.

According to certain embodiments, the solid anion exchanger is not in full contact with the first ion exchange membrane, especially not in the region where the cathode on the opposite side of the first ion exchange membrane contacts it to provide a fluid transfer between the first anion exchange membrane and the solid ion exchange membrane To ensure anion exchangers. It is thus also preferred according to certain embodiments that the solid anion exchanger at least in the region of the cathode on the opposite side of the first ion exchange membrane with this with 99% or less of the area of the first ion exchange membrane, preferably 97% or less, more preferably 95% or less, in particular 92% or less, is in contact with the solid anion exchanger, based on the area of the first ion exchange membrane which is in contact with the cathode.

The further mechanical design of the solid Anionenaus exchanger, which can also be understood as a filling medium, is not particularly limited, and it may be formed, for example, as a bed of solid anion exchange particles, which are not particularly limited, as a porous structure, for example, spongy, and / or as, for example, regular, porous self-supporting structure. If the solid anion exchanger is present as a bed of solid anion exchanger particles, the particles preferably have a particle size between 5 μm and 2 mm, more preferably between 100 μm and 1 mm, it being possible to determine the particle size for example with sieve analysis. According to certain embodiments, the particles are adapted to the size of the cell and / or to the corresponding flow regime. According to certain embodiments, the solid anion exchanger is present as a bed and / or a porous structure. According to certain embodiments, the solid Anionenaus exchanger, optionally with other solid constituents, such as neutral particles or cation exchangers, in Salzbrücken space forms a filling.

Examples of the mechanical design of the solid anion exchanger are e.g.

a compressed bed of e.g. pelleted,

Anionenaustauscherpartikein

a spongy porous structure

a regularly porous self-supporting structure, as it can be, for example, by casting around polymer beads with a solution of the anion exchange material of the solid Anionenaus exchanger and subsequent dissolution of the template balls he can be. However, the structure should be at least partially open or open in order to ensure an electrolyte and gas flow can.

In addition, porous carrier beats (latex beads) can also be impregnated with an anion exchange ionomer and thus function as anion exchange particles.

The bonding of a particle bed of any, for example neutral and / or uncharged, for example polymeric, particles with an anion exchange ionomer is in accordance with certain Embodiments preferred. The advantage of this method is a higher number of exchanger groups available for the transport of anions.

The solid anion exchanger serves as an open extension of the first ion exchange membrane, for example an AEM, into the volume of the salt bridge space (eg referred to as the gap volume if the salt bridge space is formed as a gap). As a result, the surface of anion-conducting constituents of the electrolysis cell, for example of bicarbonate and / or carbonate-conducting constituents of the electrolytic cell in a C0 ₂ -electrolyte, can be greatly increased. A gas, such as the CO2 released by the anode, for example, therefore covers a smaller portion of the surface of the first ion exchange membrane and therefore does not lead to ionic isolation. Far further, the solid anion exchanger has an intrinsic ionic conductivity, which can produce an additional conduction path through the salt bridge space by only solid electrolytes. In the region of the first separator, for example, not only HCCg and / or CO3 ² but also or only one anion of the electrolyte used in the salt bridge space, for example a used acid, can serve as a mobile charge carrier in the solid ion exchanger. If dilute H2SO4 is used as electrolyte at play, in the salt bridge space, the solid anion exchanger should preferably be selected such that it also has a good SCY ^2- conductance in addition to good HCCG and / or C0 _3. ² Accordingly, the material of the solid anion exchanger can be adapted not only to an anion such as HCCy and / or CCy ² , which is cathodically generated, but also to further anions, for example in the salt bridge space.

The material of the solid anion exchanger is not limited insofar as it is adapted to the first ion exchange membrane and / or an electrolyte in the salt bridge space except that it is capable of anion exchange and / or anion transport. Beispiels- The solid anion exchanger may comprise an anion exchanger resin in which cations, preferably alkali and / or alkaline earth metal cations, eg by complex formation, and / or ammonium ions and / or derivatized ammonium ions such as quaternary ammonium ions, more preferably alkali metal cations and / or ammonium ions and / or derivatized ammonium ions such as quaternary ammonium ions are immobilized. Furthermore, for example, phosphonium,

Pyridinium, piperidinium, guanidinium, imidazolium, pyrrazolium and / or sulfonium ions to be bound to a support of the solid anion exchanger.

According to certain embodiments, the solid anion exchanger in the salt bridge space comprises cations immobilized in a polymeric backbone, which cations can exchange for example hydrogen carbonate ions and / or carbonate ions, these hydrogen carbonate ions and / or carbonate ions preferably being transportable through the solid anion exchanger to provide suitable conductivity in the salt bridge space.

Anion exchangers are usually in acidic (eg in the HSO ₄ -form, where they can also be present as solid acids), neutral (eg as TFO or Cl salt) or basic form (eg HC0 ₃ form weakly basic, OH form strongly basic) in solid form. In the present invention, depending on the mode of operation, various such anion exchangers may be present side by side in a cell according to the invention, where basic anion exchangers are preferably used in the vicinity and / or on the first ion exchange membrane.

According to certain embodiments, the solid anion exchanger is basic, preferably strongly basic. According to certain embodiments, the immobilized cations of the anion exchange exchanger are such that an ion pair formed by them is always completely dissociated, which can be controlled, for example, by the pH. According to bestimm th embodiments, the solid anion exchanger Hydrogencarbonate, carbonate and / or OH ions and / or Anio NEN of the electrolyte used in the salt bridge space electrolyte, such as an acid, as counterions. This can improve the transport of bicarbonate and / or carbonate from the first ion exchange membrane by means of ion hopping (as opposed to "tunneling" as in the Grotthus mechanism).

In theory, it would also be possible in general to carry out a corresponding continuation of the action of the first ion exchange membrane with a solid, for example acidic ion exchanger and a liquid electrolyte in salt bridge space. In the special case of C0 ₂ electrolysis, however, this is not possible since basic solutions by the present CO2 are converted into neutral carbonate solutions. For the purposes of this invention, basic media are regarded as anion conductors, acidic media as proton conductors. Since in neutral (eg, alkali) carbonates the cation transport predominates, a corresponding carbonate solution that is produced does not correspond to an extension of the first Ionenaustauschermemb ran in the salt bridge space.

In certain embodiments, the solid anion exchanger is hydrophilic. As a result, it is easier to wet with an aqueous medium, so that an aqueous medium, such as an aqueous acid, can be used in the salt bridge space. In addition, the water can also serve as an additional starting material in the reduction of carbon dioxide, as stated above, and allow a good conductivity.

In addition, the first anion exchanger and / or a Fül treatment comprising the solid anion exchanger, optionally with wide ren solid components, such as neutral particles or Kat ion exchangers, in the salt bridge space also for supporting separators and / or membranes, for example, the first Ionenaustau shear membrane and the first separator, against each other. Since the filling has its own ion conductivity, the shape of the support does not lead to the isolation of electrode rich. When assembling a cell stack or cell stack, the bed can also be used for power transmission (adhesion) through the entire stack or total stack.

As already discussed, the filling contains at least in the area of the cathode / AEM a solid, e.g. strongly basic, anion exchangers. The filling may also be made entirely of a solid, e.g. strong basic, anion exchangers best hen.

It is advantageous in this case if the chemical nature of the fes th anion exchanger of the first Ionenaustauschermemb ran, for. AEM, as similar as possible. Both components can also be constructed, for example, on the same polymer base, although, for example, the chain length and / or the degree of crosslinking may differ.

Exemplary embodiments in which the salt bridge space comprises only one solid anion exchanger are shown schematically in FIGS. 1 to 3. In the figures, the first separator is shown to be in contact with the anode. However, this is not mandatory according to the invention, and the separator may also be present separately from the anode, so that an anode space can also form, for example, between the separator and the anode and, if appropriate, the anode also on an opposite side of such an anode space Space for the supply of substrate, eg of a gas.

In Fig. 1, the solid anion exchanger 4, for example, a strongly basic anion exchanger, arranged in the salt bridge space II, which is located between an anion exchange membrane AEM as the first ion exchange membrane based on egg nes, eg strong base, anion exchange material 1 and a cation exchange membrane CEM as the first separator Base of a, for example, strongly acidic cation exchange material 3 is located. The AEM is followed by the cathode K and the cathode compartment I, and the CEM is followed by the anode A and the anode compartment III. As shown in the figure, the fixed Anione 4 are penetrated by fluids such as gases and / or electrolytes. For each of the three rooms I, II, III, a supply and an exhaustion are provided.

An alternative embodiment can be found in Fig. 2, wherein the electrolytic cell largely corresponds to that of Fig. 1, except that the CEM was replaced by a diaphragm D, for example in the form of a hydrophilic gas separator 5. A further alternative embodiment can be found in Fig. 3, which also largely corresponds to the embodiment of Fig. 1, wherein the CEM was replaced by a Bipolarmembran BPM set in which a cation exchange layer based on, for. strongly acidic, cation exchange material 3 is directed towards the salt bridge space II, while an anion exchange layer based on a, e.g. strongly basic, Anionenaustauschermaterials 1 is directed towards the anode.

In addition to the solid anion exchanger but also other ingredients in the filling in the salt bridge space are possible, which can support the release of the taken in the solid anion exchanger and / or transported in bicarbonate.

Thus, the filling may e.g. next to one, e.g. strongly basic and / or weakly basic, anion exchangers, non-ionic ion exchangers, e.g. Poly-alcohols, and / or cation exchangers, e.g., weak and / or strong, include acidic cation exchangers, which are not particularly limited. Experimentally, e.g. in the examples in DE

102017211930.6 found that less than one equivalent of CO2 passes through the first ion exchange membrane, eg an AEM, into a central salt bridge space per flowed electron. This indicates not only HCO ₃ but also transport of CO ₃ ² and / or OH. Acid additions in the solid anion exchangers, such as cation exchangers, can serve for example for the conversion of CO ₃ ² into HCO ₃ . A valent ion is usually more mobile in ion exchange media, while in solution multivalent ions are more mobile. Through a such appropriate addition, an op tive highly conductive conduction path is created for each type of ion.

Fig. 4 shows schematically an exemplary embodiment in which such a filling in the salt bridge space II with a mixed ion exchange material 2 containing e.g. strongly basic, anion exchange material, which may be homogeneously mixed in example, is provided. The further embodiment of the cell in FIG. 4 corresponds to that of FIG. 1.

A comparison of these two cell concepts with, e.g. strongly basic, anion exchange material 4 (Figure 5) and mixed ion exchange material 2 containing e.g. strongly basic, anion-exchange material (FIG. 6) is also shown in FIGS. 5 and 6 with a generic separator S made of a generic material 6, which may be constructed in one or more layers. The further construction corresponds to that in FIG. 1

According to certain embodiments, the solid salt bridge space further comprises non-ionic and / or unfunctionalized particles, nonionic ion exchangers and / or cation exchangers, preferably the non-ionic and / or unfunctionalized particles, nonionic ion exchangers and / or cation exchangers, Furthermore, the non-ion-conducting and / or unfunctionalized particles and / or non-ionic ion exchangers prefer to be in an area adjacent to the first ion exchange membrane in an amount of up to 20% by volume, preferably up to 17% by volume, more preferably up to 14% by volume, still more preferably up to 10% by volume or up to 5% by volume, based on the total amount of solid anion exchanger and uncharged particles, nonionic ion exchanger and / or cation exchanger. The mixture of the solid Anionenaus exchanger with the uncharged particles, the nonionic ion exchanger and / or the cation exchanger is not particularly limited, and may be homogeneous or heterogeneous, eg in the form of layers, etc., be. The uncharged particles, nonionic ion exchangers and / or cation exchangers are not particularly limited. If the filling is constructed in the form of layers, these layers are preferably parallel to the first ion exchange membrane and / or the first separator, wherein the layer adjacent to the first ion exchange membrane contains the uncharged particles, nonionic ion exchangers and / or cation exchangers in an amount of up to 20% by volume, preferably up to 17% by volume, more preferably up to 14% by volume, even more preferably up to 10% by volume or up to 5% by volume, based on the layer, of or only comprises or contains the solid anion exchanger.

A layer adjacent to the first separator may, for example, contain the solid anion exchanger in an amount of up to 20% by volume, preferably up to 17% by volume, more preferably up to 14% by volume, even more preferably up to 10% by volume. % or up to 5% by volume, based on the layer, and according to certain embodiments, the balance may be a solid cation exchanger. A layer adjoining the first separator may also comprise or only contain only the solid cation exchange. According to certain embodiments, the salt bridge space further comprises a solid cation exchanger which is at least partially in contact with the first separator.

As already stated above for the solid anion exchanger, it is preferred in this case for the solid cation exchanger to be in contact at least in the region of the anode on the opposite side of the first separator, ie for example more than 50% of the area of the first separator more than 60%, more preferably more than 70%, in particular more than 80%, that touch this, based on the area of the first separator, which is in contact with the anode. According to certain embodiments, the solid cation exchanger is not in full contact with the first separator, especially not in the region where the anode on the opposite side of the first separator contacts it, to provide fluid transport between the first separator and the solid cation exchanger to be able to guarantee. It is thus also preferred according to certain embodiments that the solid cation exchanger at least in the region of the anode on the opposite side of the first separator with this with 99% or less of the area of the first separator, preferably 97% or less, more preferably 95% or less, in particular 92% or less, is in contact with the solid cation exchanger, based on the area of the first separator which is in contact with the anode.

It is also true for the multilayered embodiments of the salt bridge space that solid ion exchangers which do not contain any, e.g.

contain strongly basic, anion exchange materials and / or are not solid anion exchangers, preferably not in contact with the first ion exchange membrane, e.g. an AEM, are to avoid gas release at the point of contact.

According to certain embodiments, the composition of the filling must in particular be e.g. not homogeneous along the cathode-anode junction. Thus, the filling may also be layered, for example with a, e.g. strong base, solid anion exchanger or a mixture comprising the solid anion exchanger in the region of the cathode and the first ion exchange membrane, e.g. an AEM, and egg nem, e.g. strong-acid, solid cation exchanger or a mixture comprising the solid cation exchanger in the region of the anode and the first separator.

It is not fixed how many different layers can be used, nor their sequence, as long as they meet the requirement that the first ion exchange shear membrane, such as an AEM, adjacent material contains one, for example, strongly basic, anion exchanger.

For example, two or more layers may be present in such a multilayer construction of the filling, as shown by way of example in FIGS. 7 to 9 for two layers.

The cell structure with cathode K, anode A, AEM and separator S and the cathode compartment I and anode compartment III here corresponds to that of FIG. 5, and only the structure of the filling in the salt bridge space II differs. In Fig. 7, adjacent to the AEM is a layer having a, e.g. strongly basic, anion exchange material 4, while to the separator S a layer comprising a mixed ion exchange material 2 containing e.g. strongly basic, anion exchange material borders on. In Fig. 8, this mixed ion exchange material 2 containing e.g. strongly basic, anion exchange material of Fig. 7 by a, e.g. acidic or strongly acidic, cation exchange material 3 replaced. In Fig. 9, in turn, as compared to Fig. 8, the material attached to the AEM is contained by a mixed ion exchange material 2 containing e.g. strongly basic, anion exchange material has been replaced.

According to certain embodiments, the filling, even if it consists only of the solid anion exchanger, not ge closed, so that they can be traversed by an electrolyte and / or a liquid-gas bubbles mixture, so, for example. Pores or structured open spaces.

Another aspect of the present invention relates to an electrolysis system comprising an electrolyte cell according to the invention. The corresponding embodiments of the electrolytic cell as well as other exemplary components of an inventive electrolysis system he have been discussed above and thus are also applicable to the inventive electrolyte seanlage. According to certain embodiments, summarizes an electrolysis plant according to the invention a plurality of electrolysis cells according to the invention, which is not excluded concluded that next to other electrolysis cells are present.

According to certain embodiments, the electrolytic system according to the invention further comprises a recycling device, which is connected to a discharge of the salt bridge space and a supply of the cathode space, which is adapted to füh a starting material of the cathode reaction, which can be formed in the salt bridge space, again in the cathode space ren.

An electrolysis cell according to the invention is shown by way of example in Fig. 10, in which case the electrolytic cell with the Ka thodenraum I, the salt bridge space II and the anode space III, the anode A, the separator S, the cathode K and the first ion exchange membrane as AEM, for example, according to the structure can be constructed in Fig. 5 or Fig. 6. CO2 is supplied to the cathode space and CO2 removed from the cathode space, product P and possibly water are removed, the water being separated off. CO2 generated in salt bridge space and possibly CO2 transferred into the salt bridge space can be recycled via a return to the cathode space after the electrolyte j is separated from the salt bridge space, which can also be recycled. On Ano denseite an anolyte A is supplied to the anode compartment III, where anodic conversion of H2O and / or HCl to O2 and / or CI2 is shown here by way of example, wherein the Halbzel lenreaktion does not limit the invention. The other symbols in Fig. 10 are calibrated _Z conventional fluidic circuit.

According to certain embodiments, the electrolytic system according to the invention further comprises an external device for electrolyte treatment, in particular a device for removing dissolved gases from an acid, with which in particular the anolyte and / or the electrolyte are treated in the salt bridge space, for example gases such as CO2 or O2 too remove, and so allow a return of anolyte and / or the electrolyte in the salt bridge space. This is in particular special advantage if both are pumped from a common Reser voir, so there is only a common anolyte / Elektro lyt for salt bridge space reservoir, so the anolyte and the electrolyte in the salt bridge space are identical.

According to certain embodiments, the electrolytic system according to the invention comprises two separate circuits for anolyte and electrolyte in the salt bridge space, which may optionally have separate devices for electrolyte treatment, in particular devices for removing dissolved gases from an acid, or only the circuit for the Elekt rolyt in the salt bridge space a corresponding device has.

In a still further aspect, the present inven tion relates to the use of an electrolysis cell according to the invention or an electrolysis plant according to the invention, which can also include a plurality of electrolysis cells according to the invention, for the electrolysis of CO ₂ and / or CO.

In addition, disclosed is a method for the electrolysis of CO ₂ , wherein an electrolysis cell according to the invention or an inven tion proper electrolysis plant is used, wherein CO _{2 is} reduced at the cathode and at the cathode resulting bicarbonate and / or carbonate through the first Ionenaus exchange membrane to an electrolyte in Salt bridge space wan changed, wherein the hydrogen carbonate and / or carbonate is also transported by the solid anion exchanger in the salt bridge space away from the first ion exchange membrane.

In addition to hydrogen carbonate and / or carbonate in this case is not excluded that also formate and / or acetate and / or other resulting anions migrate membrane through the first ion exchange membrane in the electrolyte of the salt bridge space. The process according to the invention is carried out with the electrolysis cell according to the invention or the electrolysis plant according to the invention. Consequently, all discussed with regard to the inven tion proper electrolysis cell and the Elekt rolyseanlage invention features are also applicable to the inventive Shen method. In particular, the cathode compartment, the cathode, the first ion exchange membrane, the anode compartment, the anode, the separator, the salt bridge compartment and the solid anion exchanger, as well as other components, have already been discussed with regard to the electrolysis cell according to the invention and the electrolysis plant according to the invention. The corresponding features can thus be carried out according to the inventions to the invention process. Conversely, if the process according to the invention is carried out with the electrolysis cell or the electrolysis plant according to the invention, embodiments and aspects of the process according to the invention for the electrolysis of CCg in this application can also be found, for example with regard to an electrolyte in the salt bridge space and the concomitant developments the components of the electrolysis cell, such as the first separator.

CCg is electrolyzed with the process according to the invention, although it is not excluded that on the cathode side in addition to CCg another reactant such as CO is present, wel Ches can also be electrolyzed, ie a mixture is present, which includes CO2, and CO, for example. For example, contains a reactant on the cathode side at least 20 vol.% CO2, eg at least 50 or at least 70 vol.% CO2 _, and in particular the educt on the cathode side to 100 vol.% CO2 · In principle, the electrolysis cell according to the invention can also implement pure CO, wherein then, however, no CO2 is released in the salt bridge area.

In the process of the invention, the filling comprising the solid anion exchanger or consisting of the solid An ion exchanger of an electrolyte, that is, a liquid medium, flows through. The electrolyte is not particularly However, according to certain embodiments, it is still aqueous. Thus, according to certain embodiments, the salt bridge space comprises an aqueous electrolyte. It may be the anolyte and / or catholyte, if present, ent speak or different from these.

According to certain embodiments, the electrolyte of the salt bridge space comprises an acid, preferably a water-soluble or water-miscible acid. According to certain embodiments, the electrolyte contains at least 10 ^-6 mol / l H ⁺ and / or its hydrated variants, preferably at least 10 ^-4 mol / l, more preferably at least 10 ^-3 mol / l, even more preferably at least 10 ^-2 mol /1. According to certain embodiments, the electrolyte of the salt bridge space comprises substantially no mobile cations other than H ⁺ and / or its hydrated variants. Preferably, according to certain embodiments, the electrolyte does not comprise any mobile cation except protons, apart from mobile cations in a quantity of common impurities. The electrolyte serves to discharge the C02 and to keep the filling moist.

The at least one acid in the electrolyte in the salt bridge space is not particularly limited, but is preferably a water-soluble and / or water-miscible acid, such as HCl, HBr, HI, H2SO4, H3PO4, HTfO (trifluoromethanesulfonic acid), etc. By the Use of at least egg ner acid in the electrolyte, the C02 release from Hydro gencarbonat and / or carbonate in the solid anion exchanger, such as a basic or strongly basic ion exchanger, favors. The release of the CO2 preferably takes place in the volume of the salt bridge space and not at the contact surface between the filling comprising the solid anion exchanger or the solid anion exchanger and the separator, since this would also be associated with high voltage losses.

According to certain embodiments, improved gas release in the salt bridge space can be achieved by using more layered fillings, as described above, can be achieved. It is also possible, of course, in the salt bridge room

To build electrolyte gradient in order to achieve a preferred Freiset tion in salt bridge space and not on separators as ers th ion exchange membrane, the first separator and possibly other separators contained and / or ion exchange membranes, for example, with multiple electro lytzuführungen to the salt bridge space or layers of Füllun conditions , where, if necessary, laminar flows for creating sol cher electrolyte gradients are possible.

According to certain embodiments, the filling comprising the solid anion exchanger or consisting of the solid anion exchanger is preferably ion-conductive in order to improve the charge transport through the electrolyte.

It is not excluded in the process according to the invention, the only verwen water as electrolyte in the salt bridge space. For this purpose, however, the first separator is preferably designed as an ion exchanger membrane comprising a cation exchanger, for example as a cation exchange membrane (CEM), or as a bipolar membrane (BPM). Preferably, the solid filling in addition to the solid anion exchanger then also contains acidic components, e.g. Cation exchanger. However, because of the conductivity, it is preferable to use an acid solution.

If the first separator is designed as a diaphragm, the electrolyte in the salt bridge space comprises at least one acid, since the diaphragm is not intrinsically ion-conducting. The Elekt electrolyte of the salt bridge space may in this case for example correspond to the anolyte, but also be different.

A particularly preferred embodiment of the method according to the invention results from the use of the solid anion exchanger, if appropriate in a mixture with further constituents in the filling of the salt bridge space, in combination with an acidic electrolyte. This can be compared to Prior art, the contact area between the Anione exchanger of the first ion exchange membrane and acidic media are greatly increased. In solutions according to the prior art, for example in US 2017037522 Al and DE

102017208610.6, the surface of the first Ionenaustau shear membrane is always the transition to the acidic medium. The water transition is moved according to the invention in the volume of Salzbrue ckenraums and thereby the surface massively magnification ßert. As a result, the insulating effect of emerging gas bubbles in C0 ₂ electrolysis has a less negative effect on the cell voltage. The effect of the anion exchanger / transporter contained in the first ion exchange membrane as a transporter for anions can be continued by filling in the salt bridge space.

According to certain embodiments, the anode compartment comprises an anolyte which comprises a liquid and / or dissolved acid, preferably wherein the anolyte and / or the acid in the salt bridge space or the electrolyte in the salt bridge space no mo bile cations except protons and / or deuterons, in particular no metal cations. According to certain embodiments, an acid in the salt bridge space does not comprise mobi len cations except protons and / or deuterons, in particular no metal cations. According to certain embodiments, the anolyte does not encompass mobile cations except protons and / or deuterons, especially no metal cations. Mo bile cations here are cations which are not bound by a chemical bond to a support, and / or in particular an ion mobility of more than

1 -1CT ⁸ m ² / (s -V), in particular more than 1 -1CT ¹⁰ m ² / (s -V). According to certain embodiments, in the anodic half reaction, no mobile cations except "D ⁺ ,

H ⁺ ", especially metal cations, released or he witnesses. In such a case, therefore, for example, for the special case of 0 ₂ evolution at the anode water (in particular in the case CCM anode) or acids with non-oxidised cash anions Anolyte or reagent may be suitable for halogen generation at the anode. especially for this case, the halogen-hydrogen acids HCl, HBr and / or HI suitable, for example halide salts are not suitable when using a diaphragm as the first separator membrane, but used when using a bi-polar membrane as the first separator membrane can be. The use of SCg in the anolyte for the production of sulfuric acid, or H ₂ O for the production of H ₂ O ₂ , etc., is possible.

An exemplary method according to the invention will subsequently be explained with reference to a specific embodiment of the electrolytic cell of FIG. 5, which will be further elaborated below. The statements here relate to a specific embodiment of the electrolytic cell of Figure 5, so that the following explanations are not limited to the embodiment shown in Fig. 5, which is described above, ken. In such an exemplary method, the cathode space I is separated from the salt bridge space II by a composite of a CO ₂ reducing cathode K and an AEM.

The cathode compartment I is flowed through by, for example moistened, CO ₂ , which is thereby reduced, for example, to CO, C ₂ H ₄ . The moistened C0 ₂ stream represents the substrate supply of the cathode. In the sense of a classic three-chamber cell, it represents the catholyte.

The salt bridge space II is separated from the anode space III by the first separator S (eg diaphragm, bipolar membrane, cation-conducting membrane) in combination with the anode A, wherein - as stated above, it is also possible for the anodization space III to be direct connects to the first separator. The salt bridge space II is packed with a permeable solid filling which contains a, e.g. contains strongly basic, Anionenaus exchanger, and is flowed through by an electrolyte flow, which may include an acid in addition to water.

The first separator can be made freely from, for example, a cation exchange membrane (CEM), a non-intrinsically ion-conducting hydrophilic gas separator (diaphragm) or a bipolar Membrane (BPM), in which preferably the anion-conducting layer is oriented towards the anode, to be selected. When using a diaphragm, the electrolyte in the anode compartment III and the liquid electrolyte in the salt bridge compartment II are preferably identical and conductive.

The anode compartment III is flowed through by the anolyte, eg aqueous HCl, aqueous H ₂ SO ₄ , H ₂ O, etc., which can supply the anode A with substrate. If the electrolyte of the salt bridge space and the anolyte have been selected to be identical, they can also be obtained from a common reservoir, but in particular suitable devices are provided to prevent carryover of dissolved gases (degassing), for example when the electrolyte is returned.

As indicated above, notwithstanding Fig. 5, the Ano denraum III also be located between the anode A and the first Separa tor S. In such a case, however, the anolyte must be conductive.

The cathode space I and the anode space III may also include, for example, electrically conductive, eg not closed, structures that serve to contact the electrodes. If the anode is not at the first separator, the requirement of conductivity can be omitted here. Preferably, the anolyte contains only salts and thus mobile "non H ⁺ " cations, when the first separator is a bipolar membrane.

The electrochemical conversion at the anode is not further limited, wherein it preferably leads to the transfer of H ⁺ from (Bi polar membrane) or through (diaphragm or CEM) the first separator in the electrolyte of the salt bridge space.

The above embodiments, embodiments and Weitererbil applications can, if appropriate, combine with each other. Further possible refinements, developments and implementations of the invention also include combinations of previously or below which are not explicitly mentioned with respect to the embodiments described features of the invention. In particular, the person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the present invention.

Claims

claims

1. electrolysis cell, comprising

a cathode compartment comprising a cathode;

an anode compartment comprising an anode; and

a first separator adjacent to the anode compartment;

2. electrolytic cell according to claim 1, wherein the solid Anio exchanger in the salt bridge space comprises cations which are immobilized in a polymeric skeleton, wherein the cations in particular bicarbonate and / or carbonate ions can exchange.

3. electrolysis cell according to claim 1 or 2, wherein the solid anion exchanger is present as a bed and / or porous structure.

4. An electrolytic cell according to any one of the preceding claims, wherein the solid salt bridge space further comprises uncharged particles, nonionic ion exchangers and / or cation exchangers, preferably the uncharged particles, not ionic ion exchanger and / or cation exchanger, more preferably the uncharged particles and / or not ionic ion exchangers in an area adjacent to the first ion exchange membrane in an amount of up to 20% by volume, based on the total amount of solid anionic ion exchangers and uncharged particles, non ionic ion exchangers and / or cation exchangers.

5. electrolytic cell according to one of the preceding claims, wherein the first separator is a cation exchange membrane, a bipolar membrane or a diaphragm.

6. electrolytic cell according to any one of the preceding claims, wherein the solid anion exchanger is basic, preferably strong ba, is.

7. An electrolytic cell according to any one of the preceding claims, wherein the solid anion exchanger is hydrophilic.

8. electrolytic cell according to one of the preceding claims, wherein the salt bridge space further comprises a solid cation exchange shear, which is at least partially in contact with the first Se parator.

9. electrolysis plant, comprising an electrolytic cell according to one of claims 1 to 8.

10. electrolysis plant according to claim 9, further comprising a recirculation device, which is connected to a discharge of the salt bridge space and a supply of the cathode space, which is adapted to lead a reactant of the cathode reaction, which can be formed in the salt bridge space, back into the cathode space ,

11. A method for the electrolysis of CCy, wherein an electrolytic cell according to any one of claims 1 to 8 or a sys- tem according to claim 9 or 10 is used, wherein CCg is reduced at the cathode and formed at the cathode of bicarbonate and / or carbonate by the first Ionenaus exchange membrane to an electrolyte in the salt bridge space wan changed, wherein the bicarbonate and / or carbonate is also transported by the solid anion exchanger in the salt bridge space away from the first ion exchange membrane.

12. The method of claim 11, wherein the salt bridge space comprises an aqueous electrolyte.

13. The method of claim 11 or 12, wherein the electrolyte of the salt bridge space comprises an acid, preferably a water-soluble or water-miscible acid.

14. The method according to any one of claims 11 to 13, wherein the electrolyte of the salt bridge space substantially no mobile

Cations except H ⁺ and / or its hydrated variants to summarizes.

15. Use of an electrolytic cell according to any one of claims 1 to 8 or an electrolysis system according to claim 9 or

10 for the electrolysis of CCg and / or CO.