FR3079510A1 - METHOD AND DEVICE FOR ELECTROCHEMICALLY COMPRESSING GASEOUS HYDROGEN - Google Patents

Abstract

The invention relates to an improved method for the electrochemical compression of gaseous hydrogen, at low pressure, for example a pressure P ° of 1 to 30 bar, the pressure P1 referred to being between 700 and 900 bar, for example for reloading. a tank of a vehicle operating with an internal combustion engine using hydrogen as fuel or with an electric motor powered by a fuel cell. To do this, the method essentially consists of implementing an electric generator, an enclosure containing an electrolyte and several EH / CE electrode counter-electrode pairs and, if appropriate, at least one separator arranged between EH and CE, in which one ensures that the electrolyte contains at least one intermediate vector A, which is the oxidant of a redox couple (A / B); and it implements: a step of hydrogen injection at P ° so that at the anode EH: H2 → 2H + + 2e-, that at the cathode CE: A + ne- → B with n = 1-10; and a step comprising reverse polarity for EH and CE to induce electrochemical transformation; so that at the anode CE: B → A + ne- with n = 1-10 ,, that at the cathode EH: 2H + + 2e- → H2, this hydrogen accumulating in the enclosure to a pressure P1> P °. The invention also relates to devices for implementing such a production method and a kit comprising one of these devices and electrolyte components.

Description

METHOD AND DEVICE FOR ELECTROCHEMICAL COMPRESSION OF GAS HYDROGEN

Technical area

The field of the invention is that of the electrochemical compression of hydrogen gas. The invention relates in particular to an electrochemical compression method of H ₂ , for example to go from a pressure of a few bars or a few tens of bars to a pressure of several hundred bars.

The invention also relates to a device for implementing this method, as well as a kit comprising the device and all or part of the consumables useful in said method.

State of the art - Technical problem

Hydrogen gas is the cleanest and most efficient fuel for producing energy in both a fuel cell and an internal combustion engine.

The electricity produced by the fuel cell is a source of energy making it possible to generate hydrogen again by electrolysis, according to an ecologically virtuous loop of renewable energy.

These qualities are particularly appreciable for applications of hydrogen as fuel for transport vehicles, in which the hydrogen stored in the vehicle produces kinetic energy by means of an internal combustion engine whose fuel is hydrogen. and / or an electric motor powered by an on-board fuel cell consuming hydrogen.

Furthermore, the storage of energy in the form of hydrogen under pressure is also particularly advantageous.

Hydrogen is an invisible, odorless, non-toxic gas. Its consumption in a fuel cell produces only electrical energy and water, while its combustion does not lead to harmful by-products.

In this context, hydrogen appears to be the most suitable energy vector to support the energy transition, in particular to allow clean mobility as well as energy storage.

To do this, hydrogen must be manufactured from electricity and water: these are the conventional alkaline electrolysis or solid electrolyte processes with a proton exchange membrane (Proton Exchange Membrane), or in development such as high temperature electrolysis.

The use of hydrogen for clean mobility requires the ability to store pressurized hydrogen in tanks on board vehicles, at high pressures ranging from 200 to 700 bar.

The conventional method is to compress the gas with a mechanical compressor; it is a difficult and expensive operation.

Compressors are devices that have been used for a very long time in the implementation and marketing of hydrogen, which is done with standard cylinders of type B50 or B100 at 200 bar inflation pressure. Since hydrogen has been considered as a fuel for motor vehicles, the filling pressures for on-board tanks have been raised to 350, 700 or even 820 bars, which means that future service stations will need to have distribution systems at around 900 bars. These pressures are achievable with multi-stage mechanical compressors but the operating and maintenance requirements of these mechanical compressors and therefore of the associated moving components cannot be met in a certain number of configurations and locations of the stations (for example located in isolated sites).

An alternative to mechanical compressors is the electrochemical compression of hydrogen as described for example in patent applications WO03075379A1, US2004040862A1 and FR3007669A1. The principle is based on the use of an electric current to oxidize, at the anode An, gaseous hydrogen low pressure BP, in the form of protons in an anode compartment, to migrate the protons through a membrane Mb and reduce them , cathode C, in hydrogen gas in a cathode compartment. However, from a practical point of view, when there is a large pressure differential between the cathode compartment and the anode compartment, the membranes are generally gas permeable and / or do not support this pressure difference. The cathode compartment cannot therefore rise in pressure.

FIG. 1 appended illustrates the principle of electrochemical compression of hydrogen by a cell comprising, successively from left to right, a low-pressure anode compartment BP, an anode A and a cathode C between which a membrane Mb is interposed, and high pressure cathodic behavior HP. This cell is a membrane / electrode assembly (AME). The membrane Mb separating two anode and cathode electrodes, respectively, is a “proton exchange membrane”, made up of a proton conducting polymer, for example an ionomer of type PF SA (PerFluoroSulfonic Acid) such as Nafion®. The electrodes generally include platinum or a platinum alloy supported by carbon.

The device according to FR3007669A1 aims to solve the problem of water accumulation at the anodes of the electrochemical cells of said compressor. It has in fact been found that as the hydrogen pressure increases in a compressor, the quantity of water necessary to ensure the electrochemical reactions decreases. However, an accumulation of water interferes with the passage of hydrogen through the membranes of electrochemical cells by blocking access to the electrodes and by exerting pressure on the membranes. The solution proposed by the device according to FR3007669A1 is an electrochemical compressor with several stages, capable of pressurizing hydrogen and comprising: - an inlet and an outlet of hydrogen; - at least two membrane-electrode assemblies (AME), each membrane-electrode assembly forming an electrochemical cell; said MEAs being arranged so as to be traversed by a flow of hydrogen, and being connected in series with each other and electrically isolated from each other; each of the MEAs comprising an active surface capable of ensuring the oxidation-reduction reactions of the hydrogen; MEAs with active surfaces distinct from each other, and decreasing according to the direction of circulation of the hydrogen.

This device according to FR3007669A1 remains perfectible in terms of improving the permeability of the membranes and / or their resistance to pressure.

Furthermore, it is known that conventional alkaline-type electrolysers produce hydrogen saturated with water, that is to say containing, for example, 2.3% of water at 20 ° C., and other types of 'impurities in gaseous form (O2, N2, Ar ...). This pollution of the hydrogen thus produced is a drawback, since it may require additional costly drying and / or purification steps.

Objectives of the invention

In this context, the present invention aims to satisfy at least one of the objectives set out below.

-One of the essential objectives of the present invention is to provide an improved process for electrochemical compression of gaseous hydrogen, at low pressure, for example a pressure P ° of 1 to 30 bars which is typically that of the hydrogen produced by an alkaline or proton-conducting membrane electrolyser, the pressure P ¹ referred to at the electrochemical compression outlet being at least 150 bars, for example between 300 and 1000 bars, even between 700 and 900 bars, for example for recharging '' a tank of a vehicle operating with an internal combustion engine using hydrogen as fuel or with an electric motor powered by a fuel cell.

One of the essential objectives of the present invention is to provide an improved method of electrochemical compression of hydrogen gas, which makes it possible to overcome the problem of the permeability of the membranes and / or their resistance to pressure as well as the problem accumulation of water in electrochemical compressors.

One of the essential objectives of the present invention is to provide an improved process for the electrochemical compression of hydrogen gas, which makes it possible to purify and dry the gas if it contains gaseous impurities.

One of the essential objectives of the present invention is to provide an improved method of electrochemical compression of hydrogen gas, which is simple and static, which makes it possible to operate on isolated sites where it is not possible to ensure the operation and maintenance of mobile mechanical systems, and which is therefore economical in terms of maintenance.

One of the essential objectives of the present invention is to provide an improved process for the electrochemical compression of hydrogen gas, which is safe.

One of the essential objectives of the present invention is to provide an improved process for electrochemical compression of gaseous hydrogen, the implementation of which is possible in a non-industrial environment and not controlled by specialized operators, that is to say say on a hydrogen gas distribution site, completely independently.

One of the essential objectives of the present invention is to provide an improved process for the electrochemical compression of hydrogen gas, which makes it possible to have an instantaneous flow rate sufficient for filling a hydrogen tank and / or, for all unless you have a gas buffer tank with the lowest possible capacity.

One of the essential objectives of the present invention is to provide an improved process for the electrochemical compression of hydrogen gas, which is in line with environmental constraints.

-One of the essential objectives of the present invention is to provide an industrial device, reliable, efficient, economical and robust, for the implementation of the method as referred to in one of the objectives above.

Brief description of the invention

These objectives, among others, are achieved by the present invention which relates, in the first place, to a method of electrochemical compression of gaseous hydrogen essentially consisting in implementing at least one electric generator, at least one enclosure containing at least one electrolyte and at least one electrochemical cell - preferably several - comprising:

a hydrogen electrode E ^H , a counter electrode CE, at least one electrolyte in which E ^H and CE are immersed, and, optionally, at least one separator separating the electrolyte in which E ^h is immersed, the electrolyte in which is CE dive;

in which :

SE ^h and CE are likely to be connected to the generator terminals, • S the electrochemical cell is likely to be supplied with hydrogen at a pressure P ° and to collect hydrogen at a pressure P ¹ > P ° after compression electrochemical;

and in which:

• We make sure that the electrolyte in which CE is immersed contains at least one intermediate vector A, which is the oxidant of a redox couple (A / B);

• We implement:

1) a step of injecting hydrogen at a pressure P ° in and / or in the vicinity of the hydrogen electrode E ^H , during which the hydrogen electrode E ^H is the anode and the counter electrode CE is the cathode, E ^H and CE are polarized so:

that at the anode E ^H : H ₂ -> 2H ⁺ + 2e ', that the ions H ⁺ migrate from E ^H towards CE, that at the cathode CE: A + ne' — ► B with n natural integer, preferably between 1 and 10, and more preferably still between 1 and 3;

2) a step comprising an inversion of polarity in which the polarity of E ^H and CE is inverted so that E ^H plays the role of the cathode and CE the role of the anode; in order to:

than at the CE anode: B -> A + ne 'with n natural integer, preferably between 1 and 10 to, and, more preferably still between 1 and 3;

that the H ⁺ ions migrate from CE to E ^H ;

that at the cathode E ^H : 2H ⁺ + 2e '-> H ₂ , this hydrogen accumulating in the electrochemical cell at a pressure P ¹ > P °.

It is to the credit of the inventors to have imagined to decouple the electrochemical compression reaction in two stages, which makes it possible to have an electrochemical cell under pressure and therefore to be able to generate hydrogen under high pressure. Decoupling in two stages is made possible by the addition of an intermediate vector A, which is the oxidant of a redox couple A / B.

This makes the process according to the invention an electrochemical compression technique which is economical, reliable, efficient, eco-compatible and suitable, inter alia, for the supply, repeatedly, of limited volumes of hydrogen gas under pressure, as could be the case in service stations allowing the supply of gaseous hydrogen under pressure to tanks of vehicles equipped with internal combustion engines using hydrogen as fuel or electric motors powered by a fuel cell.

In this regard, the compression method according to the invention indeed integrates a storage function making it possible to drastically reduce the volume of the gas buffer tank (of a service station for example). Hydrogen is stored in chemical form (H +) in solution at low temperature and at atmospheric pressure.

In this context of relocation of hydrogen distribution units and therefore of compression systems for this gas, it is also essential that this compression of hydrogen at high pressure takes place in the strictest respect of safety rules. In this respect, one of the key points is the explosiveness of the hydrogen / oxygen gas mixture.

By these innovative arrangements, the method according to the invention and more generally the system according to the invention which comprises the method and the device, perfectly integrates this security constraint.

In addition, the process incorporates a purification and drying function. In fact, knowing that the hydrogen to be compressed used in the process according to the invention may contain water vapor (for example, in the case where it is obtained by means of conventional alkaline type electrolysers which produce l hydrogen saturated with water, that is to say containing eg 2.3% water at 20 ° C), and other types of impurities in gaseous form (O2, N2, Ar ..

However, thanks to the high pressure values achieved by the process according to the invention, the dew point of a gas decreases drastically. It therefore follows that the hydrogen at the outlet contains very little water (for example, 49 ppm of H ₂ O at 700 bars at 20 ° C.). In addition, the operating mode in two steps makes it possible to evacuate gases other than hydrogen at the end of the ^st step, and outputting only hydrogen.

According to a preferred arrangement of the invention, during step 2, the difference Dp between the pressure P ° of the hydrogen admitted into the electrochemical cell and the pressure P ¹ of the hydrogen produced (pressure delivered at the outlet of the electrochemical cell) is such that (in bars): 1 <Dp <1000 preferably 5 <Dp <500.

In another of its aspects, the present invention relates to a device in particular for implementing the method according to this same invention.

This device includes:

a) at least one electric generator,

b) at least one enclosure containing at least one electrolyte and at least one electrochemical cell - preferably several - comprising:

a hydrogen electrode E ^H , a counter electrode CE, at least one electrolyte in which E ^H and CE are immersed, and, optionally, at least one separator separating the electrolyte in which E ^H is immersed, of the electrolyte in which is CE dive;

in which :

ν 'E ^h and CE are likely to be connected to the terminals of the generator, ν' the electrochemical cell is likely to be supplied with hydrogen at a pressure P ° and to collect hydrogen at a pressure P ¹ > P ° after electrochemical compression,

c) possibly means for increasing the G / L interface,

d) optionally means for heating the electrolyte (or electrolytes) in the enclosure.

This simple and efficient device, the main function of which is the compression of hydrogen gas, eliminates or minimizes the use of mechanical compressors which are sources of high investment and operating costs. Due to the compression mode specific to the invention, this device does not require a moving part like the piston compressors and therefore is a source of savings in terms of maintenance.

This device allows the storage of hydrogen in chemical form H ⁺ in solution, which offers the possibility of delivering hydrogen under high pressure without resorting to large volumes of gas under pressure.

It is important to note that if a separator (for example an ion exchange membrane) is necessary, it is an equipression separator, without any problem of gas permeability, since only one gas is produced at each stage.

Another object of the invention relates to a kit for implementing the method comprising a device and at least part of the components for the preparation of the electrolyte or electrolytes intended to be contained in the enclosure or enclosures of the device .

Definitions

Throughout this presentation, any singular means either a singular or a plural.

The definitions given below by way of example may be used in the interpretation of this presentation:

• electrolyte: aqueous solution or ionic liquid containing ions Y ^{y +} , Y ^y ', H ⁺ , OET • acid electrolyte: pH <7 (+/- 0.1) • basic electrolyte: pH> 7 (+/- 0,1) • E °: standard potential. The standard E ° potentials referred to in this presentation are all measured under the same conditions (reference, temperature, concentrations).

• Efi ': thermodynamic potential of the electrochemical reaction.

• E: potential out of equilibrium of the electrochemical reaction, equal to the addition of the thermodynamic potential and the overvoltage of the electrochemical reaction.

• decoupled: qualifies the implementation of the process according to 2 separate and independent steps; the first of these steps being a step of producing H ⁺ ions from gaseous hydrogen under low pressure P °; the second of these steps being an electrochemical compression step by reduction of the H + ions produced in step 1);

• approximately or approximately means to within plus or minus 10%, or even plus or minus 5%, relative to the unit of measurement used;

• between ZI and Z2 means that one and / or the other of the terminals Zl, Z2 is included or not in the interval [Zl, Z2],

Detailed description of the invention

PROCESS

Figure 2 attached schematically illustrates the principle of electrochemical compression in 2 stages, according to the invention.

During the first step, the low pressure hydrogen BP is injected into an electrochemical cell comprising a hydrogen electrode E ^H , a counter electrode CE and at least one electrolyte. More precisely, the hydrogen is injected into and / or in the vicinity of the hydrogen electrode E ^H (preferably with gas diffusion) which plays the role of anode An. The counter electrode CE is the cathode during the 'Step 1.

These two electrodes E ^H and CE are in contact with the electrolyte, in which the reduction of the intermediate vector A takes place in B, during this step 1.

In certain operating modes of the process, the electrochemical cell may include at least one interstitial separator which separates the electrolyte in which the hydrogen electrode E ^H is immersed from the electrolyte in which the counter electrode CE is immersed. The separator is not subjected to a pressure differential imposing unacceptable structural constraints. There is indeed the same pressure on both sides of the separator during the 2 stages.

In the second step, the polarity of the electrodes is reversed. The protons are reduced to hydrogen gas on the hydrogen electrode E ^H , which becomes cathode C, and the reducer B is oxidized to A at the counter electrode CE, which becomes An anode. The hydrogen gas accumulates and becomes compresses in the electrochemical cell, so that the pressure changes to a high pressure HP.

Different joining modes

F.l - Operation Fl (see Figure Fl attached)

In this operating mode F1, the thermodynamic potential E _t h (A / B) of the redox couple (A / B) is lower than that E _t h (H ⁺ / H2) of the redox couple (H ⁺ / H2) in the middle acid or to that E _t h (H ₂ O / H ₂ ) of the redox couple (H ₂ O / H ₂ ) in basic medium.

The first step then consists of an electrolysis reaction and the second step of a spontaneous electrochemical reaction.

F il Première, variant _de _FJ_j_CA / Bj_e_st_un_c_ouple_R_edox_fM ^m 7M). (see Figure Fl.l attached)

In this first variant:

1) step 1) is an electrolysis of at least one salt of M ^{m +} of at least one metal M present in the electrolyte, in which M ^{m +} is reduced to metal M at the cathode CE and is deposited on that -this, while H ₂ is oxidized to H ⁺ at the anode E ^H ,

2) step 2) comprises an oxidation of the metal M deposited on the anode CE which redissolves into M ^{m +} ions in the electrolyte and a production of hydrogen H ₂ at the cathode E ^H.

In the first step of this operating mode F. 1, the invention uses the property that certain metals or alloys have of kinetically blocking the release of hydrogen: this is the phenomenon called hydrogen overvoltage, leading to a state electrochemical out of balance. The overvoltage of the reaction of evolution of hydrogen on the metal M must be sufficient so that the reaction of reduction of M ^{m +} in M is kinetically favored compared to the reaction of production of hydrogen. This means that the absolute value of the overvoltage of the hydrogen evolution reaction on the metal M is preferably greater than the difference Eth (H ⁺ / H2) - E _t h (M ^{m +} / M) in an acid medium or at difference E _t h (H ₂ O / H ₂ ) - E _t h (M ^{m +} / M) in basic medium.

The second step consists in generating hydrogen gas in the electrochemical cell, by attacking the metal vector which redissolves in solution. It is a question of implementing the solutions making it possible to restore the state of equilibrium, that is to say to dissolve the metal M into salt M ^{m +} and to release the hydrogen gas by releasing the energy accumulated during from step 1).

According to a remarkable arrangement of the invention, the redox couple (A / B) corresponds to: (M ^{m +} / M), M being a metal, preferably selected from the group comprising - ideally consisting of -: Zn; Cd; Sn, Ni, Mn, Fe, Pb, Co, Hg, their alloys and mixtures, Zn being particularly preferred.

F.1.2 2 ^e _variante de_Fl _: _ (A / B) is un_çoupl_e_Redç> x_ (l7_Ç) (confer Figure Fl.2 attached)

In this ^2nd embodiment where A and B are molecules or ions and wherein a separator is introduced into the electrochemical cell and separates the electrolyte in which is immersed the electrode E ^H, the electrolyte in which is immersed the CE electrode;

1) step 1) is an electrolysis of at least one salt of I ¹ present in the electrolyte, in ii '| which I is reduced to I at the cathode CE, while H ₂ is oxidized to H at the anode E ^H , i ¹ i

2) step 2) comprises an oxidation of I into I at the CE anode and in the electrolyte as well as a production of hydrogen H ₂ at the cathode E ^H , by reduction of H ⁺ .

ii ¹

On a remarkable arrangement of the invention, the redox couple (A / B) corresponds to: (1 / I), I being an atom or group of atoms and i & i 'being electronic charges, with I il> I i'I;

ii ¹ (I / I) being preferably selected from the group comprising [ideally consisting of]: Fe; U; Cr; S; V; (V ³⁺ / V ²⁺ ), [Fe (CN) e] ³ 7 [Fe (CN) e] ² 'being particularly preferred.

i i '

In the first step, the electrolysis reaction reduces the I ions to I ions at the CE electrode.

i ¹ i

The presence of the separator is a means of preventing the reoxidation of the ions I into I at the electrode E ^H.

i ¹ i

During the second step, the I ions are oxidized to I ions

F.2 - F2 operation (see Figure F2 attached)

In this operating mode F.2, the thermodynamic potential E _t h (A / B) of the redox couple (A / B) is greater than that E _t h (H ⁺ / H2) of the redox couple (H ⁺ / H2) in an acid medium or to that E _t h (H ₂ O / H ₂ ) of the redox couple (H ₂ O / H ₂ ) in basic medium. In addition, a separator is arranged between the electrolyte in which E ^H (hydrogen compartment) is immersed and the electrolyte in which CE is immersed.

From which it follows that:

1) step 1) comprises a reduction from A to B at the cathode CE and an oxidation at the anode E ^H of the hydrogen gas contained in the hydrogen compartment,

2) step 2) is an electrolysis in which B is oxidized to A at the anode CE, while in the hydrogen compartment, H ⁺ is reduced to H ₂ at the cathode E ^H.

The first step is a spontaneous reaction, and the second step is an electrolysis reaction.

During the first step, the CE electrode is cathodically polarized, and the E ^H electrode is anodically polarized via an electronic charge.

During the second step, a power supply provides the electrical energy necessary to perform electrolysis.

On a remarkable arrangement of the invention, the redox couple (A / B) is chosen from the group consisting of:

• (M ^{m +} / M), M being a metal, preferably selected from the group comprising - ideally consisting of -: Cu, Mn, Ag their alloys and their mixtures, Cu being particularly preferred;

ii ¹ • (1 / I), I being an atom or group of atoms and i & i 'being electronic charges, with I il> I i'I; (Γ / Γ) being preferably selected from the group comprising [ideally consisting of]: Fe, V, Mn; iron and vanadium being particularly preferred.

***

Whatever the operating mode, the compression process includes a storage function allowing the volume of the gas buffer tank (of a petrol station for example) to be drastically reduced. Hydrogen is stored in chemical form in solution at low temperature and at atmospheric pressure.

Separator (case Jpnçtipnnement, of the 2 ^nd variant of FlU F2)

Advantageously, the separator is an ion exchange membrane.

It may, for example, be a proton membrane of the NAFION® type, or an anionic membrane of the IONAC® MA3475 type.

Electrolyte

According to the invention, the electrolyte can be an acidic or basic aqueous solution, or an ionic liquid, in which the gases under pressure are less soluble than in an aqueous medium.

The electrolyte is preferably an aqueous saline solution comprising the ions of the metal M or of the component A of the Redox couple (A / B) and at least one acid or a Bronsted base.

Advantageously, the ions of the metal M or of the component A of the Redox couple (A / B) are brought into the electrolyte by at least one precursor, preferably chosen from the group ideally comprising: - the salts, in particular the sulfates , oxides, nitrates, chlorides, citrates, phosphates, carbonates, fluorides, bromides, oxides, aqueous solutions of hydroxide of alkali metals or alkaline earth metals or their mixtures.

Long-term intermediate chemical storage of hydrogen.

According to a 1 ^st remarkable implementation mode of the invention, the process is interrupted between step 1) and step 2), to make room for a hydrogen storage in chemical form H ⁺ in solution in electrolyte in the electrochemical cell, this storage being preferably accompanied by the disconnection of the electrodes CE and E ^H.

According to a ^2nd mode remarkable implementation of the invention, the process is interrupted between step 1) and step 2), to make room for a hydrogen storage in chemical form H ⁺ in solution in 'electrolyte, out of the enclosure by transfer of the electrolyte charged with H ⁺ in an external tank.

Settings. of process

Preferably, step 1) is carried out at a temperature between 10 and 90 ° C, preferably between 20 and 80 ° C and, more preferably still, between 25 and 60 ° C.

In the context of the invention, an implementation mode is preferred in which, during step 1) for operation F1 or step 2) for operation F2, the generator delivers a density to the electrodes E ^H and CE of current i, expressed in A per m ² of electrode area, of between 100 and 5000, preferably between 200 and 3000 and, more preferably still, between 300 and 2500.

Possibility of downstream storage

According to an advantageous embodiment of the invention, the gaseous hydrogen thus produced is collected at the pressure Pl> P ° and stored outside the enclosure.

This storage can take place in any suitable high pressure container, in particular in terms of capacity.

Process variant for increasing the diffusion of dissolved hydrogen

According to an advantageous possibility of the invention, the interface between the undissolved gas phase G and the liquid phase L - hereinafter called the G / L interface - is increased at least during step 2), so as to accelerate the diffusion of the liquid phase towards the gas phase, dissolved hydrogen saturating, even supersaturing, the electrolyte.

This arrangement has the effect of remedying what limits the production of hydrogen gas, namely, on the one hand, the solubilization of hydrogen in the electrolyte, in particular in the electrolyte formed by an aqueous solution containing ions. as well as H ⁺ or OH 'ions and, on the other hand, the possible supersaturation of the electrolyte into dissolved hydrogen.

Advantageously, the interface is increased by implementing at least one of the following operations:

(i) the forced circulation which preferably consists in generating a flow of electrolyte in the enclosure, more preferably, using at least one pump so as to evacuate and renew the gas bubbles present on the 'electrode or electrodes and on any roughness of the enclosure;

(ii) (ii) at least partial substitution of the dissolved hydrogen by at least one neutral gas, by injection of the latter into the enclosure to generate bubbles of neutral gas intended to evacuate and renew the gas bubbles present on the 'electrode or electrodes, and / or on any roughness of the enclosure;

(iii) partial decompression which consists in isolating the storage tank from the enclosure to increase the pressure of hydrogen gas in the latter; then when this pressure is higher than that in the storage tank, the enclosure is decompressed, which creates or increases the supersaturation of H ₂ in the electrolyte and therefore promotes the germination of bubbles;

(iv) spraying the electrolyte into fine droplets in the gaseous sky of the enclosure, (v) at least one heating, preferably at least one localized heating, of the electrolyte, which advantageously consists in locally reducing the solubility dissolved hydrogen gas, to thus promote the nucleation of bubbles, (vi) the diffusion of ultrasound in the electrolyte to generate bubbles, (vii) at least one depolarization, preferably at least one localized depolarization of the electrolyte, to locally increase the supersaturation and to promote the formation of bubbles, (viii) the use of nanoparticles and / or at least one porous nucleating material in the electrolyte, to promote the nucleation of bubbles and increase the number of bubble germination sites, (ix) mechanical agitation of the electrolyte which promotes nucleation of the bubbles by supplying the energy necessary to counter the surface tension.

Etapecomplémentairefacultative

Possibility of downstream storage:

According to an advantageous embodiment of the invention, the gaseous hydrogen thus produced is collected at the pressure Pl> P °, then stored outside the enclosure.

This storage can take place in any suitable high pressure container, in particular in terms of capacity.

Device

In another of its aspects, the present invention relates to a device in particular for implementing the method according to the invention. This device includes:

a) at least one electric generator,

b) at least one enclosure containing at least one electrolyte and at least one electrochemical cell - preferably several - comprising:

a hydrogen electrode E ^H , a counter electrode CE, at least one electrolyte in which E ^H and CE are immersed, and, optionally, at least one separator separating the electrolyte in which de E ^H is immersed, of the electrolyte in which CE is immersed;

SE ^h and CE being capable of being connected to the terminals of the generator,

Ά the electrochemical cell being capable of being supplied with hydrogen at a pressure P ° and of collecting hydrogen at a pressure P ¹ > P ° after electrochemical compression,

c) possibly means for increasing the G / L interface;

d) possibly means for heating and / or cooling the electrolyte (or electrolytes) in the enclosure.

In one of its preferred embodiments, the device according to the invention is characterized in that:

the enclosure is a pressure-resistant reactor in which are arranged a plurality of electrochemical cells each comprising a pair of electrodes E ^h and CE, and in that it comprises:

a) optionally, a source of hydrogen, preferably at least one reservoir containing hydrogen, to supply the cells;

b) at least one electrolyte container;

c) means for circulating the electrolyte (or electrolytes) in the cells of the reactor, these means preferably including the electrolyte container, so that circulation takes place between the reactor and this container;

d) optionally at least one degassing flask connected to the reactor, by at least one pipe fitted with at least one valve, for collecting high pressure hydrogen produced in the cells; this degassing flask containing a volume of electrolyte;

e) optionally at least one conduit connecting the degassing flask to the electrolyte container, this conduit comprising at least one valve for regulating the volume of electrolyte in the degassing flask;

f) optionally at least one high pressure hydrogen storage tank thus obtained.

This embodiment is particularly suitable for the compression of large volumes of hydrogen with the particularly advantageous possibility of intermediate storage in the form of protons in solution.

This robust, reliable, economical, safe and efficient device integrates perfectly into industrial or off-site equipment for the production of hydrogen under high pressure, especially for applications in the fields of clean mobility and energy storage. For example, this device could be associated with a hydrogen production system on an industrial site or in a localized manner in a gas station to recharge hydrogen vehicles.

In accordance with a remarkable arrangement of the invention:

o the hydrogen electrodes E ^H are produced from a material advantageously chosen from transition metals, lanthanides and / or alkaline earths and, more preferably still, from the group comprising - and ideally composed of -: platinum and platinoids in the form of metal or oxide, tungsten, titanium, zirconium or molybdenum in the form of oxide, carbide, sulfide or borides, silver, nickel, iron, cobalt and alloys based on at least one or these elements, the composites formed by one of these elements or an alloy with an oxide, carbon-based materials (fine carbon particles, organometallic material, graphene) and combinations of these materials.

o Preferably, the electrodes E ^H are doped with metallic elements, for example in the form of thin layers and / or nanoparticles, the metallic elements being selected from: platinum, platinoids, nickel, molybdenum, tantalum, tungsten, for example under metallic form, in the form of carbides or sulfides; the CE counter electrodes are made from a material advantageously chosen from the group of metals and / or metal alloys, comprising -and ideally composed of-: Al, Pb and alloys of Pb, titanium, carbon-based materials, nickel, and / or iron, stainless steels, and combinations of these materials;

KIT

The present invention also relates to a kit for implementing the method. This kit is characterized in that it includes:

o the device according to the invention;

o and the components for the preparation of the electrolyte intended to be contained in the enclosure of the device.

This kit, which forms a packaging unit for sale, may also include an explanatory notice for the implementation of the process using the device and the components contained in this kit.

Examples

Example 1: Illustration of the first variant F. 1.1 of the operation F1 according to the invention: (A / B) is a Redox couple ÎM ^! / M): (Zn ²⁺ / Zn) E ° (Zn ²⁺ / Zn) = -0.76 V <E ° (ΙΓ / Η2) = 0 V

In the example which follows, hydrogen was compressed from P ° = 1 bar to P ^{1 =} 200 bars in an electrochemical reactor composed of two electrodes immersed in an acidic aqueous solution (electrolyte). See attached Figure F 1.1.

The two 1 m ² surface electrodes are as follows:

• A CE electrode or counter electrode, made of aluminum, on which the metal is deposited during the first step;

• A hydrogen electrode E ^H on which the gaseous hydrogen is oxidized, during the first step, and on which the hydrogen is released during compression during the second step. E ^H consists of a porous metallic material of stainless steel type 304, the surface of which is doped with a thin deposit of molybdenum sulfide, which plays the role of catalyst in the electrochemical conversion of hydrogen to protons in the liquid phase, and vice versa.

The electrolyte is composed of zinc ions (concentration 100 g / L) and sulfuric acid (250 g / L). The temperature is set at 30 ° C.

In the first step, a power supply is connected between the cathode and the anode. It provides a current density of 595 A / m ² for 5 h, which makes it possible to deposit 3267 g of zinc on the cathode (with a yield of 90%) and to oxidize 100 g of H ₂ gas at 1 bar .

During the second step, the cathode is electrically connected to the H ₂ electrode. The rate of evolution of hydrogen is 21.5 g / h / m ² , and it takes 4.40 hours to produce 100 g of hydrogen at 200 bars.

Example 2: Illustration of the operation F2 according to the invention: (A = Cu ⁺⁺ / B = Cu) _E ° (Cu ⁺⁺ / Cu)> E ° (lfi / H2) = 0V

This operation can be implemented with the Cu ²⁺ / Cu couple in sulfuric acid medium. A volume of 1 Nm ³ of hydrogen at atmospheric pressure was compressed from P ° = 1 bar to P ¹ = 350 bar in an electrochemical reactor composed of two electrodes immersed in an acidic aqueous solution (see attached Figure F2).

The two 1 m ² surface electrodes are as follows:

• A CE electrode or counter electrode, made of 316L stainless steel, on which the metal is deposited during the first step, • A hydrogen electrode E ^H on which the hydrogen gas oxidizes during the first step, and on which the hydrogen is released during compression during the second step. E ^H consists of a porous carbon felt material, the surface of which is doped with platinum nanoparticles, which act as a catalyst in the electrochemical conversion of hydrogen to protons in the liquid phase, and vice versa.

An anionic membrane of the lonac MA3475 type is placed between the two electrodes.

The temperature is fixed at 50 ° C.

The electrolyte in the stainless steel electrode compartment (CE counter electrode) is made up of copper ions (concentration 100 g / L) and sulfuric acid (190 g / L). It is prepared by mixing 19.25 kg of sulfuric acid (37.5%, Brenntag) in 15.42 L of deionized water, then adding to this mixture 15.09 kg of copper sulphate CuSO4, 5H2O) (99% , Sigma Aldrich).

The electrolyte in the hydrogen compartment of E ^H is composed of sulfuric acid (190 g / L). It is prepared by mixing 19.25 kg of sulfuric acid (37.5%, Brenntag) in 22.96 L of deionized water.

In the first step, a power supply is connected between the cathode and the anode. Hydrogen is supplied to the gas electrode at a rate of 0.25 g / min. During this first step, the following reactions take place:

At the gas electrode (anode): H ₂ = 2H ⁺ + 2e 'E ° = 0V (1)

At the copper electrode (cathode): Cu ²⁺ + 2e '= Cu (s) E ° = 0.34V (2)

Note that this spontaneous reaction is subject to additional electrochemical activation to accelerate the kinetics. The power supply provides a current density of 400 A / m ² for 5h56, which makes it possible to deposit 2651 g of copper on the cathode (with a yield of 94%) and to oxidize 83 g of H ₂ gas to 1 bar. The membrane prevents the deposition of copper at the anode.

In the second step, the polarity of the electrodes is reversed, and the deposited copper is redissolved while producing hydrogen at the gas electrode. The membrane is necessary to avoid the deposition of copper at the cathode.

At the copper electrode (anode): Cu (s) = Cu ²⁺ + 2e 'E ° = 0.34V (3)

At the gas electrode (cathode): 2H ⁺ + 2e '= H2 E ° = 0V (4) [In reactions (2) & (3) above, the symbol s of Cu (s) means solid, that is, it corresponds to a metallic deposit.]

During this second step, a power supply is connected between the cathode and the anode. It provides a current density of 400 A / m ² for 5h35, which dissolves all of the copper on the stainless steel electrode (anode) and reduces 83 g (41.71 mol) of H ₂ gas to 350 bars at a hydrogen evolution rate of 0.0021 mol.s '^ m' ² During this 2nd stage, the released hydrogen then rises under pressure as the reaction progresses, to reach a pressure P ¹ 350 bars. The hydrogen can then be collected in a tank or used directly.

Claims (15)

1. A method of electrochemical compression of gaseous hydrogen consisting essentially in using at least one electric generator, at least one enclosure containing at least one electrolyte and at least one electrochemical cell-preferably several comprising: a hydrogen electrode E ^H , a counter electrode CE, at least one electrolyte in which E ^H and CE are immersed, and, optionally, at least one separator separating the electrolyte in which E ^h is immersed, the electrolyte in which is CE dive; in which : JE ^h and CE are likely to be connected to the terminals of the generator, J the electrochemical cell is capable of being supplied with hydrogen at a pressure P ° and of collecting hydrogen at a pressure P ¹ > P ° after electrochemical compression; and in which: • We make sure that the electrolyte in which CE is immersed contains at least one intermediate vector A, which is the oxidant of a redox couple (A / B); • We implement: 1) a step of injecting hydrogen at a pressure P ° in and / or in the vicinity of the hydrogen electrode E ^H , during which the hydrogen electrode E ^H is the anode and the counter electrode CE is the cathode, E ^H and CE are polarized, so - that at the anode E ^H : H ₂ 2H ⁺ + 2e ', that the ions H * migrate from E ^H towards CE, that at the cathode CE: A + ne'-> B with n natural integer, from preferably between 1 and 10, and more preferably still between 1 and 3; 2) a step comprising -> an inversion of polarity in which the polarity of E ^H and CE is inverted by ensuring that E ^H plays the role of the cathode and CE the role of the anode; in order to: than at the CE anode: B -> A + ne ’with n natural integer, preferably between 1 and 10, and more preferably still between 1 and 30; - that the H + ions migrate from CE to E ^H , that at the cathode E ^H : 2H ⁺ + 2e '- »H2, this hydrogen accumulating in the electrochemical cell at a pressure P ¹ > P °. 2. Method according to claim 1 characterized in that during step 2, the difference Dp between the pressure P ° of the hydrogen admitted into the electrochemical cell and the pressure P ¹ of the hydrogen produced (pressure delivered at the outlet of the electrochemical cell) is such that (in bars): 1 <Dp <1000 preferably 5 <Dp <500. 3. Method according to claim 1 or 2 characterized in that the thermodynamic potential Eth (A / B) of the redox couple (A / B) is less than that Eth (H ⁺ / H2) of the redox couple (H ⁺ / H2) in an acid medium or to that Eth (H ₂ O / H2) of the redox couple (H ₂ O / H ₂ ) in basic medium. 4. Method according to claim 3 characterized in that the redox couple (A / B) is chosen from the group consisting of: • (M ^{m +} / M), M being a metal, preferably selected from the group comprising - ideally consisting of -: Zn; Cd; Sn, Ni, Mn, Fe, Pb, Co, Hg, their alloys and mixtures, Zn being particularly preferred; • (17 I ¹ ), I being an atom or group of atoms and i & i 'being electronic charges, with I il> I i'I; (17 Γ) preferably being selected from the group comprising [ideally consisting of]: Fe; U; Cr; S; V; (V ³⁺ / V ²⁺ ), [Fe (CN) 6] ³ '/ [Fe (CN) ₆ ] ² ' being particularly preferred. 5. Method according to claim 3 and claim 4, characterized in that (A / B) is a Redox couple (M ^{m +} / M) and in that: 1) step 1) is an electrolysis of at least one salt of M ^{m +} of at least one metal M present in the electrolyte, in which M ^{m +} is reduced to metal M at the cathode CE and is deposited on that -ci, while H2 is oxidized to H ⁺ at the anode E ^H , 2) step 2) comprises a redissolution of the metal M deposited on the anode CE into ions M ^{m +} in the electrolyte and a production of hydrogen H2 at the cathode E ^H. 6. Method according to claim 3 and claim 4, characterized in that (A / B) is a Redox couple (17 I ¹ ), in that a separator is introduced into the electrochemical cell and separates an electrolyte EL1 in which is immersed the electrode E ^H , of an electrolyte EL2 in which the electrode CE is immersed, and in that: 1) step 1) is an electrolysis of at least one salt of Γ present in the electrolyte EL2 in which the CE electrode is immersed, in which Γ is reduced to T at the CE cathode, while H2 is oxidized to H ⁺ at the anode E ^H , 2) step 2) comprises an oxidation of I ¹ to I ¹ at the CE anode and in the electrolyte EL2 in which the CE electrode is bathed, as well as a production of hydrogen H2 at the cathode E ^H , in the electrolyte EL1 in which the hydrogen electrode E ^{H is} bathed, by reduction of the H ⁺ . 7. Method according to claims 1 or 2 characterized in that the thermodynamic potential Ε * (Α / Β) of the redox couple (A / B) is greater than that E _t j ₁ (H ⁺ / H2) of the redox couple (H ⁺ / H2) in an acid medium or in that of EthiFbOÆE) of the redox couple (H2O / H2) in basic medium, in that a separator is placed between the electrolyte in which E ^H - hydrogen compartment- and CE is immersed; and in that : 1) step 1) comprises a reduction from A to B at the cathode CE and an oxidation at the anode E ^H of the hydrogen gas contained in the hydrogen compartment, 2) step 2) is an electrolysis in which B is oxidized to A at the CE anode, while in the hydrogen compartment, H ⁺ is oxidized to H2 at the cathode E ^H. 8. Method according to claim 7 characterized in that the redox couple (A / B) is chosen from the group consisting of: • (M ^{m +} / M), M being a metal, preferably selected from the group comprising - ideally consisting of -: Cu, Mn, Ag their alloys and their mixtures, Cu being particularly preferred; • (I ¹ / I ¹ ), I being an atom or group of atoms and i & i 'being electronic charges, with I il> I i'|; (I ^{1/1 1} ) being preferably selected from the group comprising [ideally constituted by]: Fe, V, Mn; iron and vanadium being particularly preferred. 9. Method according to claim 1, 6 or 7 characterized in that the separator is an equipression membrane, preferably an ionic membrane, and, more preferably still, an anionic membrane. 10. Method according to at least one of the preceding claims, characterized in that the electrolyte is an aqueous medium or an ionic liquid. 11. Method according to claim 5 characterized in that: -> the electrolyte is an aqueous saline solution further comprising at least one acid or a Bronsted base; -> the ions of the metal M are brought into the electrolyte by at least one precursor, preferably chosen from the group comprising - ideally consisting of -: the salts, in particular the sulfates, the oxides, the nitrates, the chlorides, the citrates, phosphates, carbonates, fluorides, bromides, oxides, aqueous solutions of alkali metal hydroxides or alkaline earth metals or their mixtures 12. Method according to claim 1 characterized in that the ions of component A of the redox couple (A / B) are brought into the electrolyte by at least one precursor, preferably chosen from the group comprising - ideally consisting of: salts, in particular sulfates, oxides, nitrates, chlorides, citrates, phosphates, carbonates, fluorides, bromides, oxides, aqueous solutions of hydroxide of alkali metals or alkaline earth metals or of their mixtures, 13. Device in particular for implementing the method according to at least one of the preceding claims, characterized in that it comprises: at. at least electric generator, b. at least one enclosure containing at least one electrolyte and at least one electrochemical cell - preferably several - comprising: a hydrogen electrode E ^H , a counter electrode CE, at least one electrolyte in which E ^H and CE are immersed, and, optionally, at least one separator separating the electrolyte in which E ^H is immersed, of the electrolyte in which is CE dive; in which : JE ^h and CE are likely to be connected to the terminals of the generator, S the electrochemical cell is capable of being supplied with hydrogen at a pressure P ° and of collecting hydrogen at a pressure P ¹ > P ° after electrochemical compression vs. possibly means for increasing the G / L interface; d. possibly means for heating the electrolyte (or electrolytes) in the enclosure. 14. Device according to claim 13 characterized in that the enclosure is a pressure-resistant reactor in which are arranged a plurality of electrochemical cells each comprising a pair of electrodes E ^h and CE, and in that it comprises: a) optionally, a source of hydrogen, preferably at least one reservoir containing hydrogen, to supply the cells; b) at least one electrolyte container; c) means for circulating the electrolyte (or electrolytes) in the cells of the reactor, these means preferably including the electrolyte container, so that circulation takes place between the reactor and this container; d) optionally at least one degassing flask connected to the reactor, by at least one pipe fitted with at least one valve, for collecting high pressure hydrogen produced in the cells; this degassing flask containing a volume of electrolyte; e) optionally at least one conduit connecting the degassing flask to the electrolyte container, this conduit comprising at least one valve for regulating the volume of electrolyte in the degassing flask; f) optionally at least one high pressure hydrogen storage tank thus obtained. 15. Kit for implementing the method according to at least one of claims 1 to 12, characterized in that it comprises: o the device according to claim 13 or 14; o and the components for the preparation of the electrolyte intended to be contained in the enclosure of the device.