Water electrolysis device, membrane electrode and preparation method of membrane electrode

Abstract

The invention relates to the technical field of membrane electrodes, in particular to a water electrolysis device, a membrane electrode and a preparation method thereof.The water electrolysis device comprises the membrane electrode, the membrane electrode comprises an ion exchange membrane and a catalytic layer arranged on at least one side of the ion exchange membrane, and the catalytic layer comprises at least two active layers; two adjacent active layers are defined as a first active layer and a second active layer; the first active layer is arranged on the ion exchange membrane, the second active layer is arranged on the side, away from the ion exchange membrane, of the first active layer, and the volume average particle size D50 of the first catalyst in the first active layer is smaller than that of the second catalyst in the second active layer. By designing the distribution of gradient catalyst particles, the discharge efficiency of bubbles is improved, the material transfer resistance of the catalyst layer is reduced, the water electrolysis performance is optimized, and the energy consumption is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of membrane electrode, in particular to an electrolytic water device, a membrane electrode and a preparation method thereof. BACKGROUND

[0002] The membrane electrode is used as a channel for substance transmission and a place for electrochemical reaction in the electrolytic water device, and plays a crucial role in the electrolytic water device. The existing membrane electrode has the problem of poor water and gas transmission capacity, which is not conducive to the improvement of the performance of the membrane electrode. SUMMARY

[0003] The main purpose of the present application is to provide an electrolytic water device, which aims to improve the transmission capacity of substances in the membrane electrode and improve the performance of the electrolytic water device.

[0004] To achieve the above-mentioned purpose, the present application provides an electrolytic water device, which comprises a membrane electrode, the membrane electrode comprises an ion exchange membrane and a catalyst layer arranged on at least one side of the ion exchange membrane, and the catalyst layer comprises at least two active layers.

[0005] The two adjacent active layers are defined as a first active layer and a second active layer.

[0006] The first active layer is arranged on the ion exchange membrane, and the second active layer is arranged on the side of the first active layer away from the ion exchange membrane. The volume average particle size D50 of the first catalyst in the first active layer is smaller than the volume average particle size D50 of the second catalyst in the second active layer.

[0007] In the two adjacent active layers, the first active layer is closer to the ion exchange membrane than the second active layer, and the volume average particle size D50 of the first catalyst in the first active layer is smaller than the volume average particle size D50 of the second catalyst in the second active layer. In this way, the volume average particle size D50 of the catalyst in the catalyst layer on the surface of the ion exchange membrane gradually increases from the side close to the ion exchange membrane to the side away from the ion exchange membrane. It can be understood that the volume average particle size D50 of the first catalyst in the first active layer is smaller than the volume average particle size D50 of the second catalyst in the second active layer, and the smaller particles of the first catalyst in the first active layer mean a larger specific surface area, which can improve the catalytic capacity, and at the same time, the larger specific surface area is also conducive to the contact between the electrolyte and the catalyst particles, and improves the charge transfer efficiency. Then, the second catalyst particles with large particle size in the second active layer construct a catalyst layer with higher porosity and larger pore size, which is easy to remove the generated bubbles during the electrolytic water reaction, which is conducive to reducing the material transmission resistance of the catalyst layer, optimizing the water electrolysis performance and reducing the energy consumption.

[0008] It can be understood that in the process of hydrogen production by water electrolysis of ion exchange membrane, if the generated bubbles adhere to the surface of the active sites of the catalyst and are not discharged in time, the bubbles will occupy the active sites, hinder the reactants from reaching the catalyst sites, cause mass transfer loss, deteriorate the water electrolysis performance, and cause the current to surge to increase energy consumption. The present application solves the above problems by designing the distribution of gradient catalyst particles. Specifically, the distribution of gradient catalyst particles causes the porosity in the catalytic layer to also be distributed in a gradient, that is, the porosity in the catalytic layer gradually increases from the direction of the catalytic layer close to the ion exchange membrane to the direction of the catalytic layer away from the ion exchange membrane. In this way, it is helpful to discharge the generated bubbles in time, release the active sites, improve the mass transfer capacity of the membrane electrode, and further improve the performance of the water electrolysis device.

[0009] Optionally, the difference between the volume average particle size D50 of the first catalyst and the volume average particle size D50 of the second catalyst is in the range of 1 nm to 10 μm.

[0010] It can be understood that, in order to realize the gradually increasing trend of the volume average particle size D50 of the catalyst in the catalytic layer from the direction close to the ion exchange membrane to the direction away from the ion exchange membrane, the difference between the volume average particle size D50 of the catalyst in the first active layer and the volume average particle size D50 of the catalyst in the second active layer in the adjacent two layers in the catalytic layer is in the range of 1 nm to 10 μm, specifically, the difference between the volume average particle size D50 of the first catalyst in the first active layer and the volume average particle size D50 of the second catalyst in the second active layer is in the range of 1 nm to 10 μm. In this way, it is helpful to build the trend of gradually increasing porosity in the catalytic layer from the direction close to the ion exchange membrane to the direction away from the ion exchange membrane, and in this way, it is helpful to discharge the generated bubbles in time, release the active sites, and improve the mass transfer capacity of the membrane electrode.

[0011] Optionally, the volume average particle size D50 of the first catalyst is in the range of 0.1 nm to 100 nm; and / or, the volume average particle size D50 of the second catalyst is in the range of 11 nm to 13 μm.

[0012] It can be understood that, in order to realize the gradually increasing trend of the volume average particle size D50 of the catalyst in the catalytic layer from the direction close to the ion exchange membrane to the direction away from the ion exchange membrane, the volume average particle size D50 of the catalyst in the first active layer and the volume average particle size D50 of the catalyst in the second active layer in the adjacent two layers in the catalytic layer specifically satisfy: the volume average particle size D50 of the first catalyst is in the range of 0.1 nm to 100 nm; and / or, the volume average particle size D50 of the second catalyst is in the range of 11 nm to 13 μm.

[0013] Optionally, the at least two active layers are sequentially provided with an A active layer and a B active layer from the direction close to the ion exchange membrane to the direction away from the ion exchange membrane;

[0014] The volume average particle size D50 of the catalyst in the A active layer ranges from 0.1 nm to 10 nm.

[0015] The volume average particle size D50 of the catalyst in the B active layer ranges from 11 nm to 50 nm.

[0016] It can be understood that the concentration of substances (such as hydrogen ions) near the ion exchange membrane is relatively high, in order to improve the active site, the volume average particle size D50 of the catalyst in the catalytic layer closer to the ion exchange membrane is smaller, the specific surface area of the catalyst is increased, and specifically, at least two active layers are arranged in the direction from close to the ion exchange membrane to far from the ion exchange membrane, and the A active layer and the B active layer are sequentially arranged; the volume average particle size D50 of the catalyst in the A active layer ranges from 0.1 nm to 10 nm, that is, the A active layer is directly arranged on the ion exchange membrane, the volume average particle size D50 of the catalyst in the A active layer ranges from 0.1 nm to 10 nm, and the volume average particle size D50 of the catalyst in the B active layer ranges from 11 nm to 50 nm, which can effectively improve the active site and improve the catalytic ability of the membrane electrode.

[0017] Optionally, the second catalyst comprises a carrier and an active substance supported on the carrier, and the volume average particle size D50 of the carrier is greater than the volume average particle size D50 of the active substance.

[0018] It can be understood that the first catalyst and the second catalyst can both be high-content functional catalysts, and considering that a high-content catalyst with a large particle size has a high cost, in order to reduce the cost, the second catalyst comprises a carrier and an active substance supported on the carrier, and the volume average particle size D50 of the carrier is greater than the volume average particle size D50 of the active substance, so that the second catalyst comprises a composite catalyst, the active substance is supported on the carrier, the volume of the catalyst is increased, and the content of the active substance in the second catalyst is reduced, thereby effectively reducing the cost.

[0019] In a long-term water electrolysis process, the structure of the catalytic layer may collapse, which reduces the service life of the electrolytic cell, and the reason may be that the catalyst particles are damaged or fall off from the catalytic layer during the reaction, so that there are not enough catalyst particles in the catalytic layer to support the layered structure, and then the phenomenon of collapse of the catalytic layer occurs. The second catalyst in the application comprises a carrier and an active substance supported on the carrier, the carrier can strengthen the support strength of the catalytic layer, reduce the problem of falling off of the active substance from the catalytic layer, reduce the risk of collapse of the catalytic layer, and improve the service life of the electrolytic cell.

[0020] Optionally, at least one of the following conditions is met: the volume average particle size D50 of the carrier ranges from 11 nm to 13 μm.

[0021] The volume average particle size D50 of the active substance ranges from 0.1 nm to 500 nm;

[0022] The loading content of the active substance in the second catalyst ranges from 0% to 60%;

[0023] The carrier comprises at least one of a first metal, a first metal oxide, porous carbon, and SiO2;

[0024] The first metal comprises at least one of Pt, Ti, Zr, and Al;

[0025] The ion exchange membrane comprises a cation exchange membrane or an anion exchange membrane.

[0026] It can be understood that the volume average particle size D50 of the carrier ranges from 11 nm to 13 μm, which helps to gradually increase the porosity of the catalytic layer from the ion exchange membrane to the direction away from the ion exchange membrane, so as to help the generated bubbles to be discharged in time, release the active sites, and improve the mass transfer capacity of the membrane electrode.

[0027] The volume average particle size D50 of the active substance ranges from 0.1 nm to 500 nm, which meets the above range, and the active substance has a larger specific surface area, which helps to improve the catalytic active sites.

[0028] The loading content of the active substance in the second catalyst ranges from 0% to 60%, which meets the above range, and helps to improve the catalytic performance while reducing the cost.

[0029] The carrier comprises at least one of a first metal, a first metal oxide, porous carbon, and SiO2, and the first metal comprises at least one of Pt, Ti, Zr, and Al. It can be understood that the above carrier has good electrical conductivity and porosity, which helps to improve the conduction of matter and electrons and improve the catalytic performance.

[0030] The ion exchange membrane comprises a cation exchange membrane or an anion exchange membrane, and a person skilled in the art can select the type of ion exchange membrane according to actual needs.

[0031] Optionally, at least one of the following conditions is met:

[0032] The thickness of the first active layer is different from the thickness of the second active layer;

[0033] The difference between the thickness of the first active layer and the thickness of the second active layer ranges from 1 μm to 24 μm;

[0034] The thickness of the first active layer is less than the thickness of the second active layer;

[0035] The thickness of the first active layer ranges from 0.01 μm to 23.01 μm;

[0036] The thickness of the second active layer ranges from 1.01 μm to 24.01 μm;

[0037] The catalytic layer comprises an anode catalytic layer and / or a cathode catalytic layer;

[0038] The catalytic layer comprises an anode catalytic layer, and the first catalyst and the second catalyst comprise at least one of iridium oxide, iridium black, iridium carbon, ruthenium iridium, platinum ruthenium iridium, a mixture of iridium and iridium oxide, a mixture of iridium oxide and titanium oxide;

[0039] The catalytic layer comprises a cathode catalytic layer, and the first catalyst and the second catalyst comprise at least one of a second metal and an alloy thereof;

[0040] The second metal comprises at least one of Pt, Pd, Fe, Co, and Ni;

[0041] The material of the ion exchange membrane comprises at least one of a perfluorosulfonic acid ion polymer, a perfluorocarboxylic acid ion polymer, a composite membrane of a perfluorosulfonic acid ion polymer and a carbon nanotube, a composite membrane of a perfluorocarboxylic acid ion polymer and a carbon nanotube, a composite membrane of a perfluorosulfonic acid ion polymer and a metal oxide, and a composite membrane of a perfluorocarboxylic acid ion polymer and a metal oxide;

[0042] The mass percentage of the catalytically active substance in the first active layer is different from the mass percentage of the catalytically active substance in the second active layer;

[0043] The mass percentage of the catalytically active substance in the first active layer is greater than the mass percentage of the catalytically active substance in the second active layer;

[0044] The difference between the mass percentage of the catalytically active substance in the first active layer and the mass percentage of the catalytically active substance in the second active layer ranges from 5% to 100%;

[0045] The mass percentage of the catalytically active substance in the first active layer ranges from 5% to 100%;

[0046] The mass percentage of the catalytically active substance in the second active layer ranges from 0% to 70%.

[0047] In the present application, the thickness of the first active layer is different from the thickness of the second active layer. It can be understood that the degree of oxygen evolution reaction is different in the entire catalytic layer, and the oxygen evolution reaction requires the supply of raw materials. The thickness of the adjacent two active layers is different, which can form a fast reaction zone and a raw material supply zone in the entire catalytic layer. It can be understood that in the adjacent two active layers, the gas generated in the layer with smaller thickness can quickly diffuse to the adjacent active layer, the reaction rate of this layer is increased, and the layer with larger thickness can provide uniform current distribution and sufficient reactant supply, which provides raw materials for the adjacent layer with smaller thickness, which helps to improve the overall catalytic reaction rate.

[0048] In the present application, the difference between the thickness of the first active layer and the thickness of the second active layer is in the range of 1 μm to 24 μm. It can be understood that meeting the above range is helpful for the rapid diffusion of gas and the improvement of reaction rate.

[0049] In the present application, the thickness of the first active layer is smaller than the thickness of the second active layer. It can be understood that the adjustment of the thickness can optimize the electrochemical reaction area. By adjusting the thickness of the adjacent two active layers, the optimal reaction conditions can be provided in different areas. For example, in the process of oxygen evolution reaction, the first active layer close to the ion exchange membrane is a key reaction area, which requires a faster reaction rate. By making the thickness of the first active layer smaller than the thickness of the second active layer, the gas generated in the first active layer can quickly diffuse to the adjacent layer, and at the same time, the second active layer can provide uniform current distribution and sufficient reactant supply. In this way, the second active layer can provide raw materials for the first active layer, promoting the rapid reaction of substances in the first active layer.

[0050] In the present application, the thickness of the first active layer is in the range of 0.01 μm to 23.01 μm. It can be understood that meeting the above range is helpful for the rapid diffusion of gas and the provision of abundant active sites, which improves the catalytic performance.

[0051] In the present application, the thickness of the second active layer is in the range of 1.01 μm to 24.01 μm. It can be understood that meeting the above range can provide the second active layer with uniform current distribution and sufficient reactant supply.

[0052] In the present application, the catalytic layer includes an anode catalytic layer and / or a cathode catalytic layer. It can be understood that the structure of the above-mentioned catalytic layer with a catalyst particle size gradient distribution from the direction close to the ion exchange membrane to the direction away from the ion exchange membrane can be an anode catalytic layer, a cathode catalytic layer, or an anode catalytic layer and a cathode catalytic layer.

[0053] In the present application, the catalytic layer includes an anode catalytic layer, and the first catalyst and the second catalyst include at least one of iridium oxide, iridium black, iridium carbon, ruthenium iridium, platinum ruthenium iridium, a mixture of iridium and iridium oxide, and a mixture of iridium oxide and titanium oxide.

[0054] In the present application, the catalytic layer includes a cathode catalytic layer, and the first catalyst and the second catalyst include at least one of a second metal and an alloy thereof, and the second metal includes at least one of Pt, Pd, Fe, Co, and Ni.

[0055] In the present application, the material of the ion exchange membrane includes at least one of a perfluorosulfonic acid ion polymer, a perfluorocarboxylic acid ion polymer, a composite membrane of a perfluorosulfonic acid ion polymer and a carbon nanotube, a composite membrane of a perfluorocarboxylic acid ion polymer and a carbon nanotube, a composite membrane of a perfluorosulfonic acid ion polymer and a metal oxide, and a composite membrane of a perfluorocarboxylic acid ion polymer and a metal oxide.

[0056] In the present application, the mass percentage of the catalytically active substance in the first active layer is different from the mass percentage of the catalytically active substance in the second active layer. Considering that the reaction rates of the two adjacent active layers are different, by setting different contents of catalytically active substances in different reaction rate regions, the utilization rate of the catalytically active substance can be improved, and the reaction efficiency can be improved. For example, a high content of catalytically active substance is set in a region with high reaction rate, and a low content of catalytically active substance is set in a region with low reaction rate.

[0057] In the present application, the mass percentage of the catalytically active substance in the first active layer is greater than the mass of the catalytically active substance in the second active layer, and the first active layer is closer to the ion exchange membrane than the second active layer. The first active layer is a key reaction region, and setting the mass percentage of the catalytically active substance in the first active layer to be greater than the mass of the catalytically active substance in the second active layer helps to improve the reaction rate.

[0058] In the present application, the difference between the mass percentage of the catalytically active substance in the first active layer and the mass percentage of the catalytically active substance in the second active layer is in the range of 5% to 100%. It can be understood that meeting the above range can improve the reaction rate.

[0059] In the present application, the mass percentage of the catalytically active substance in the first active layer is in the range of 5% to 100%. It can be understood that meeting the above range helps to provide abundant active sites and improve catalytic performance.

[0060] In the present application, the mass percentage of the catalytically active substance in the second active layer is in the range of 0% to 70%. It can be understood that meeting the above range can provide uniform current distribution and sufficient reactant supply in the second active layer.

[0061] Optionally, the application also provides a membrane electrode, comprising an ion exchange membrane and a catalytic layer arranged on at least one side of the ion exchange membrane, wherein the catalytic layer comprises at least two active layers;

[0062] The two adjacent active layers are defined as a first active layer and a second active layer;

[0063] The first active layer is arranged on the ion exchange membrane, and the second active layer is arranged on the side of the first active layer away from the ion exchange membrane, wherein the volume average particle size D50 of the first catalyst in the first active layer is smaller than the volume average particle size D50 of the second catalyst in the second active layer.

[0064] Optionally, the difference between the volume average particle size D50 of the first catalyst and the volume average particle size D50 of the second catalyst ranges from 1 nm to 10 μm.

[0065] Optionally, the volume average particle size D50 of the first catalyst ranges from 0.1 nm to 100 nm.

[0066] And / or, the volume average particle size D50 of the second catalyst ranges from 11 nm to 13 μm.

[0067] Optionally, the at least two active layers are arranged in the order of an A active layer and a B active layer from the side close to the ion exchange membrane to the side away from the ion exchange membrane.

[0068] The volume average particle size D50 of the catalyst in the A active layer ranges from 0.1 nm to 10 nm.

[0069] The volume average particle size D50 of the catalyst in the B active layer ranges from 11 nm to 50 nm.

[0070] Optionally, the second catalyst comprises a carrier and an active substance supported on the carrier, wherein the volume average particle size D50 of the carrier is greater than the volume average particle size D50 of the active substance.

[0071] Optionally, the membrane electrode satisfies at least one of the following conditions:

[0072] The volume average particle size D50 of the carrier ranges from 11 nm to 13 μm.

[0073] The volume average particle size D50 of the active substance ranges from 0.1 nm to 500 nm.

[0074] The loading content of the active substance in the second catalyst ranges from 0% to 60%.

[0075] The carrier comprises at least one of a first metal, a first metal oxide, porous carbon, SiO2;

[0076] The first metal comprises at least one of Pt, Ti, Zr, Al;

[0077] The ion exchange film comprises a cation exchange film or an anion exchange film.

[0078] Optionally, the membrane electrode satisfies at least one of the following conditions:

[0079] The thickness of the first active layer is different from the thickness of the second active layer;

[0080] The difference between the thickness of the first active layer and the thickness of the second active layer ranges from 1 μm to 24 μm;

[0081] The thickness of the first active layer is less than the thickness of the second active layer;

[0082] The thickness of the first active layer ranges from 0.01 μm to 23.01 μm;

[0083] The thickness of the second active layer ranges from 1.01 μm to 24.01 μm;

[0084] The catalytic layer comprises an anode catalytic layer and / or a cathode catalytic layer;

[0085] The catalytic layer comprises an anode catalytic layer, and the first catalyst and the second catalyst comprise at least one of iridium oxide, iridium black, iridium carbon, ruthenium iridium, platinum ruthenium iridium, a mixture of iridium and iridium oxide, a mixture of iridium oxide and titanium oxide;

[0086] The catalytic layer comprises a cathode catalytic layer, and the first catalyst and the second catalyst comprise at least one of a second metal and an alloy thereof; the second metal comprises at least one of Pt, Pd, Fe, Co, Ni;

[0087] The material of the ion exchange film comprises at least one of a perfluorosulfonic acid ion polymer, a perfluorocarboxylic acid ion polymer, a composite film of a perfluorosulfonic acid ion polymer and a carbon nanotube, a composite film of a perfluorocarboxylic acid ion polymer and a carbon nanotube, a composite film of a perfluorosulfonic acid ion polymer and a metal oxide, and a composite film of a perfluorocarboxylic acid ion polymer and a metal oxide;

[0088] The mass percentage of the catalytically active substance in the first active layer is different from the mass percentage of the catalytically active substance in the second active layer;

[0089] The mass percentage of the catalytically active substance in the first active layer is greater than the mass percentage of the catalytically active substance in the second active layer;

[0090] a difference between the mass percentage of the catalytically active substance in the first active layer and the mass percentage of the catalytically active substance in the second active layer ranges from 5% to 100%;

[0091] the mass percentage of the catalytically active substance in the first active layer ranges from 5% to 100%;

[0092] the mass percentage of the catalytically active substance in the second active layer ranges from 0% to 70%.

[0093] Optionally, the application also provides a preparation method of a membrane electrode, comprising:

[0094] coating at least two layers of active layer slurry on the ion exchange membrane, the volume average particle size D50 of the catalyst in the active layer arranged on the ion exchange membrane is less than the volume average particle size D50 of the catalyst in the active layer on the side away from the ion exchange membrane;

[0095] drying and cold pressing to obtain a membrane electrode.

[0096] In the process of preparing the membrane electrode, the volume average particle size D50 of the catalyst in the active layer arranged on the ion exchange membrane is less than the volume average particle size D50 of the catalyst in the active layer on the side away from the ion exchange membrane by adjusting the volume average particle size D50 of the catalyst in the active layer slurry; in this way, the distribution of the gradient catalyst particles is designed, and the distribution of the gradient catalyst particles makes the porosity in the catalytic layer also present a gradient distribution, that is, the porosity in the catalytic layer gradually increases from the surface of the ion exchange membrane close to the ion exchange membrane to the surface of the ion exchange membrane away from the ion exchange membrane, which helps to timely discharge the generated bubbles, release the active sites, and improve the mass transfer capacity of the membrane electrode.

[0097] Optionally, the step of coating at least two layers of active layer slurry on the ion exchange membrane comprises:

[0098] mixing a first catalyst, a first ion polymer and a solvent to obtain a first active layer slurry;

[0099] mixing a second catalyst, a second ion polymer and a solvent to obtain a second active layer slurry;

[0100] coating the first active layer slurry on the surface of the ion exchange membrane to form a first active layer, and coating the second active layer slurry on the first active layer to form a second active layer.

[0101] In the step of coating at least two layers of active layer slurry on the ion exchange membrane, the first catalyst, the first ionomer and the solvent are mixed to obtain a first active layer slurry; the second catalyst, the second ionomer and the solvent are mixed to obtain a second active layer slurry; the first active layer slurry is coated on the surface of the ion exchange membrane to form a first active layer, and the second active layer slurry is coated on the first active layer to form a second active layer.

[0102] Optionally, in the step of coating the first active layer slurry on the surface of the ion exchange membrane to form a first active layer, the coating method of the first active layer slurry includes any one of the following: blade coating, spraying, blade coating transfer, and slot coating.

[0103] And / or, in the step of coating the second active layer slurry on the first active layer to form a second active layer, the coating method of the second active layer slurry includes any one of the following: blade coating, spraying, blade coating transfer, and slot coating.

[0104] Blade coating is a coating method that manually coats or automatically coats by using a doctor blade to make a thick coating film.

[0105] Spraying is a coating method that disperses a coating liquid into uniform and fine mist droplets by means of pressure or centrifugal force through a spray gun or an ultrasonic spraying device, and applies the coating liquid to the surface of a coated object. The effect of spraying is better than that of blade coating, and the stability of the catalyst, the uniformity of catalyst dispersion, and the uniformity of the thickness of the catalyst layer are all better.

[0106] Blade coating transfer is a method that first coats a catalyst slurry on a transfer substrate by blade coating, then combines the transfer substrate with an ion exchange membrane through a hot pressing process, and removes the transfer substrate to realize the transfer of the catalyst from the transfer substrate to the ion exchange membrane. Generally, the ion exchange membrane forms a relatively firm combination on the surface of the ion exchange membrane through the blade coating transfer process, the stability of the catalyst layer is the best, the porosity is the smallest, and the density is the largest, but the process is relatively complex.

[0107] Slot coating is a coating technology that presses a coating liquid out along the gap of a mold and transfers it to a moving substrate under a certain pressure.

[0108] In the process of preparing the membrane electrode of the present application, any one of blade coating, spraying, blade coating transfer, and slot coating can be used in the coating process, and a suitable coating method can be selected as needed.

[0109] Optionally, the preparation method of the membrane electrode satisfies at least one of the following conditions:

[0110] The difference between the volume average particle size D50 of the first catalyst and the volume average particle size D50 of the second catalyst is in the range of 1 nm to 10 μm.

[0111] The first catalyst has a volume average particle size D50 in the range of 0.1 nm to 100 nm;

[0112] The second catalyst has a volume average particle size D50 in the range of 11 nm to 13 pm;

[0113] The mass ratio of the first catalyst to the first ionic polymer is in the range of 10:(2 to 80);

[0114] The mass ratio of the second catalyst to the second ionic polymer is in the range of 10:(2 to 80);

[0115] The solvent includes at least one of isopropyl alcohol, methanol, ethanol, water, acetone, tetrahydrofuran;

[0116] The solid content of the first active layer slurry and the second active layer slurry is in the range of 0.2% to 60%;

[0117] The first active layer slurry and / or the second active layer slurry includes an additive, which includes at least one of polytetrafluoroethylene, carboxymethyl cellulose, polyperfluoroalkyl alkenes.

[0118] It can be understood that, in general, the higher the solid content of the catalyst slurry, the more densely the catalyst particles are distributed in the catalyst layer, and the smaller the voids. This is because the increase in solid content leads to more contact between catalyst particles, reducing the gap between particles. Therefore, a catalyst slurry with high solid content can form a more dense catalyst layer during spraying or coating. The voids of the catalyst layer also have an impact on catalyst performance. Smaller voids can provide more active surface area, increasing the opportunity for contact between the catalyst and the reactants, thereby promoting reaction efficiency. In addition, smaller voids can also provide better proton transport channels. The solid content of the first active layer slurry and the second active layer slurry is in the range of 0.2% to 60%, which can improve the catalytic performance.

[0119] In the present application, the water electrolysis device comprises a membrane electrode, the membrane electrode comprises an ion exchange membrane and a catalytic layer arranged on at least one side of the ion exchange membrane, the catalytic layer comprises at least two active layers; the two adjacent active layers are defined as a first active layer and a second active layer; the first active layer is arranged on the ion exchange membrane, and the second active layer is arranged on the side of the first active layer away from the ion exchange membrane; the volume average particle size D50 of the first catalyst in the first active layer is smaller than the volume average particle size D50 of the second catalyst in the second active layer. That is, in the two adjacent active layers, the first active layer is closer to the ion exchange membrane than the second active layer, and the volume average particle size D50 of the first catalyst in the first active layer is smaller than the volume average particle size D50 of the second catalyst in the second active layer, so that the volume average particle size D50 of the catalyst in the catalytic layer on the surface of the ion exchange membrane gradually increases from the direction close to the ion exchange membrane to the direction away from the ion exchange membrane. It can be understood that the volume average particle size D50 of the first catalyst in the first active layer is smaller than the volume average particle size D50 of the second catalyst in the second active layer, and the smaller particles of the first catalyst in the first active layer mean a larger specific surface area, which can improve the catalytic ability, and at the same time, the larger specific surface area is also beneficial to the contact between the electrolyte and the catalyst particles, improving the charge transfer efficiency; then, the second active layer is constructed by the second catalyst particles with large particle size, and the porosity of the catalytic layer constructed by the second catalyst particles with large particle size is higher and the pore size is larger, which is easy to remove the generated bubbles during water electrolysis reaction, is beneficial to reduce the material transfer resistance of the catalytic layer, optimize the water electrolysis performance and reduce the energy consumption, and improve the performance of the water electrolysis device. BRIEF DESCRIPTION OF DRAWINGS

[0120] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained according to the structures shown in the drawings without creative labor for those skilled in the art.

[0121] Figure 1 is a structural schematic diagram of a membrane electrode of an embodiment of the present application;

[0122] Figure 2 is a structural schematic diagram of a membrane electrode of another embodiment of the present application;

[0123] Figure 3 is a structural schematic diagram of a membrane electrode of still another embodiment of the present application;

[0124] Figure 4 is a structural schematic diagram of a membrane electrode of yet another embodiment of the present application;

[0125] Figure 5is a schematic diagram of a microstructure of a membrane electrode according to an embodiment of the present application;

[0126] Figure 6 is a schematic diagram of a flow of a method of manufacturing a membrane electrode.

[0127] BRIEF DESCRIPTION OF DRAWINGS

[0128]

[0129]

[0130] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments in conjunction with the accompanying drawings. DETAILED DESCRIPTION

[0131] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0132] Hereinafter, the preparation method of lithium sulfide, the battery and the lithium sulfide according to the present application will be specifically disclosed with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known well and repeated description of substantially the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided in order for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0133] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0134] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0135] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0136] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0137] In the field of proton exchange membrane electrolysis (PEMWE) water materials, much research has focused on developing novel catalysts, which is undoubtedly crucial for the advancement of PEMWE. In fact, the oxygen evolution and hydrogen evolution reactions occur within the catalyst layer, which is composed of catalyst particles and ionomers, exhibiting a porous network structure. The microstructure of the catalyst layer provides channels for water / gas and proton / electron transport, determining the catalytic performance and durability of the membrane electrode.

[0138] Traditional catalyst layer structures suffer from insufficient transport pores, resulting in poor water and gas conductivity.

[0139] To address the aforementioned problems, this invention proposes a water electrolysis device. The device includes a membrane electrode, which comprises an ion exchange membrane and a catalyst layer disposed on at least one side of the ion exchange membrane. The catalyst layer comprises at least two active layers. Two adjacent active layers are defined as a first active layer and a second active layer. The first active layer is disposed on the ion exchange membrane, and the second active layer is disposed on the side of the first active layer facing away from the ion exchange membrane. The volume average particle size D50 of the first catalyst in the first active layer is smaller than the volume average particle size D50 of the second catalyst in the second active layer.

[0140] Ion exchange membranes, such as proton exchange membranes, are a special type of ion exchange membrane that allows protons (such as hydrogen ions) to pass through, but does not allow electrons and other ions to pass through.

[0141] A catalyst layer is a layered structure that has catalytic function.

[0142] The catalyst layer includes at least two active layers, and the catalyst layer can be two active layers (e.g., Figure 1 (as shown), three active layers, four active layers (as shown) Figure 2 (as shown), five active layers (such as) Figure 3 As shown in the figure, the active layer refers to a layer structure containing catalytically active substances.

[0143] The two adjacent active layers are the first active layer and the second active layer. This means that the two adjacent active layers are the first active layer and the second active layer, respectively. It can be understood that the first active layer and the second active layer can be two active layers in contact.

[0144] The first active layer is disposed on the ion exchange membrane, and the second active layer is disposed on the side of the first active layer away from the ion exchange membrane. This means that the first active layer is closer to the ion exchange membrane than the second active layer. It can be understood that the first active layer can be directly disposed on the surface of the ion exchange membrane or indirectly disposed on the surface of the ion exchange membrane. For ease of understanding, as... Figure 1 As shown, layer 20 can be the first active layer, and layer 30 can be the second active layer. It can also be understood that other active layers are placed between the first active layer and the ion exchange membrane. For ease of understanding, as shown... Figure 2 As shown, layer 30 can be the first active layer, and layer 40 can be the second active layer. That is, as... Figure 1 As shown, in one embodiment, the first active layer is directly disposed on the surface of the ion exchange membrane 10, and the second active layer is disposed on the side of the first active layer opposite to the ion exchange membrane 10; as Figure 2As shown, in another embodiment, the first active layer is indirectly arranged on the surface of the ion exchange membrane 10, and a layer structure is arranged between the first active layer and the ion exchange membrane 10, which can be an active layer, and the second active layer is arranged on the side of the first active layer away from the ion exchange membrane.

[0145] The volume average particle size D50 is the particle size corresponding to the cumulative particle size distribution percentage of 50% of a sample. Its physical meaning is that the particles with a particle size greater than it account for 50%, and the particles with a particle size less than it also account for 50%. D50 is also called the median diameter or median particle size.

[0146] In the two adjacent active layers, the first active layer is closer to the ion exchange membrane than the second active layer, and the volume average particle size D50 of the first catalyst in the first active layer is smaller than the volume average particle size D50 of the second catalyst in the second active layer, so that, as shown, Figure 5 the volume average particle size D50 of the catalyst in the catalytic layer on the surface of the ion exchange membrane gradually increases from the direction close to the ion exchange membrane to the direction away from the ion exchange membrane. It can be understood that the volume average particle size D50 of the first catalyst in the first active layer is smaller than the volume average particle size D50 of the second catalyst in the second active layer. The smaller particles of the first catalyst in the first active layer mean a larger specific surface area, which can improve the catalytic ability, and at the same time, the larger specific surface area is also beneficial to the contact between the electrolyte and the catalyst particles, improving the charge transfer efficiency. Then, the larger particle size of the second catalyst particles in the second active layer constructs a catalytic layer with higher porosity and larger pore size, which is easy to remove the generated bubbles during water electrolysis reaction, which is beneficial to reduce the mass transfer resistance of the catalytic layer, optimize the water electrolysis performance and reduce the energy consumption.

[0147] It can be understood that in the process of water electrolysis of the proton exchange membrane to produce hydrogen, if the generated bubbles adhere to the surface of the active sites of the catalyst and are not timely removed, the bubbles will occupy the active sites, hinder the reactants from reaching the catalyst sites, cause mass transfer loss, deteriorate the water electrolysis performance, and cause the current to surge to increase the energy consumption. The present application solves the above problems by designing a gradient distribution of catalyst particles. Specifically, the gradient distribution of catalyst particles causes the porosity of the catalytic layer to also have a gradient distribution, that is, the porosity of the catalytic layer gradually increases from the direction close to the ion exchange membrane 10 to the direction away from the ion exchange membrane 10 on the surface of the ion exchange membrane 10. Therefore, it is helpful to timely remove the generated bubbles and release the active sites, improve the mass transfer capacity of the membrane electrode, and improve the performance of the water electrolysis device.

[0148] In an embodiment, the difference between the volume average particle size D50 of the first catalyst and the volume average particle size D50 of the second catalyst is in the range of 1 nm to 10 μm.

[0149] Understandably, to achieve a gradual increase in the volume average particle size (D50) of the catalyst in the catalyst layer from near to far from the ion exchange membrane, the difference in volume average particle size (D50) between the catalysts in the first and second active layers of the catalyst layer ranges from 1 nm to 10 μm. Specifically, the difference in volume average particle size (D50) between the first catalyst in the first active layer and the second catalyst in the second active layer ranges from 1 nm to 10 μm. This helps to create a catalyst layer with a gradually increasing porosity from near to far from the ion exchange membrane, which facilitates the timely removal of generated bubbles, releases active sites, and improves the mass transfer capacity of the membrane electrode.

[0150] The values ​​in the range of 1nm to 10μm include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 50nm, 100nm, 500nm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, etc., as well as the range values ​​between any two of the above point values.

[0151] For example, in one embodiment, such as Figure 3 As shown, in the membrane electrode 100, the catalyst layer includes five active layers, namely, active layer A 20, active layer B 30, active layer C 40, active layer D 50, and active layer E 60, which are sequentially disposed on the ion exchange membrane 10. For example, the difference in volume average particle size D50 between adjacent active layers A 20 and B 30 is 1 nm, the difference in volume average particle size D50 between adjacent active layers B 30 and C 40 is 50 nm, the difference in volume average particle size D50 between adjacent active layers C 40 and D 50 is 500 nm, and the difference in volume average particle size D50 between adjacent active layers D 50 and E 60 is 1 μm. Of course, in another embodiment, the difference in volume average particle size D50 of the catalyst between adjacent active layers D 50 and active layers E 60 can be 10 μm, or other active layers, such as active layer F, can be further provided on the surface of active layer E 60, wherein the difference in volume average particle size D50 of the catalyst between adjacent active layers E 60 and active layers F can be 10 μm. This application does not limit the specific difference in volume average particle size D50 of the catalyst between two adjacent active layers. When implementing this scheme, those skilled in the art can set it according to the specific circumstances.

[0152] In one embodiment, the volume average particle size D50 of the first catalyst ranges from 0.1 nm to 100 nm; and / or, the volume average particle size D50 of the second catalyst ranges from 11 nm to 13 μm.

[0153] It is understandable that, in order to achieve a gradual increase in the volume average particle size D50 of the catalyst in the catalyst layer from the direction closest to the ion exchange membrane to the direction furthest from the ion exchange membrane, the volume average particle size D50 of the catalyst in the two adjacent active layers of the catalyst layer specifically satisfies the following: the volume average particle size D50 of the first catalyst ranges from 0.1 nm to 100 nm; and / or, the volume average particle size D50 of the second catalyst ranges from 11 nm to 13 μm.

[0154] The values ​​in the range of 0.1nm to 100nm include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 0.1nm, 0.2nm, 0.3nm, 0.4nm, 0.5nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1nm, 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, etc., as well as the range values ​​between any two of the above point values.

[0155] The values ​​in the range of 11nm to 13μm include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 11nm, 15nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, etc., as well as the range values ​​between any two of the above point values.

[0156] For example, in one embodiment, such as Figure 3 As shown, the volume average particle size D50 of the catalyst in active layer A 20 is 0.1 nm, the volume average particle size D50 of the catalyst in active layer B 30 is 1.1 nm, the volume average particle size D50 of the catalyst in active layer C 40 is 100 nm, the volume average particle size D50 of the catalyst in active layer D 50 is 3 μm, and the volume average particle size D50 of the catalyst in active layer E 60 is 13 μm.

[0157] In an embodiment, the at least two active layers are sequentially arranged from the direction close to the ion exchange membrane to the direction away from the ion exchange membrane as an A active layer and a B active layer; the volume average particle size D50 of the catalyst in the A active layer ranges from 0.1 nm to 10 nm; and the volume average particle size D50 of the catalyst in the B active layer ranges from 11 nm to 50 nm.

[0158] It can be understood that the concentration of the substance near the ion exchange membrane is relatively high, and in order to improve the active site, the volume average particle size D50 of the catalyst in the catalytic layer closer to the ion exchange membrane is smaller, and the specific surface area of the catalyst is increased. Specifically, the at least two active layers are sequentially arranged from the direction close to the ion exchange membrane to the direction away from the ion exchange membrane as an A active layer and a B active layer; the volume average particle size D50 of the catalyst in the A active layer ranges from 0.1 nm to 10 nm, that is, the A active layer is directly arranged on the ion exchange membrane, the volume average particle size D50 of the catalyst in the A active layer ranges from 0.1 nm to 10 nm, and the volume average particle size D50 of the catalyst in the B active layer ranges from 11 nm to 50 nm, which can effectively improve the active site and improve the catalytic ability of the membrane electrode.

[0159] In the above 0.1 nm to 10 nm, the values include the minimum value and the maximum value of the range, and every value between the minimum value and the maximum value, and specific examples include but are not limited to the point values in the embodiments and 0.1 nm, 0.2 nm, 0.3 nm, 0.4 nm, 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, etc., and the range value between any two point values.

[0160] In the above 11 nm to 50 nm, the values include the minimum value and the maximum value of the range, and every value between the minimum value and the maximum value, and specific examples include but are not limited to the point values in the embodiments and 11 nm, 12 nm, 13 nm, 14 nm, 1 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 22 nm, 23 nm, 25 nm, 27 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, etc., and the range value between any two point values.

[0161] In an embodiment, the second catalyst includes a carrier and an active substance supported on the carrier, and the volume average particle size D50 of the carrier is greater than the volume average particle size D50 of the active substance.

[0162] It can be understood that the first catalyst and the second catalyst can both be high-content functional catalysts (for example, iridium oxide catalysts), and considering that the high-content catalysts with large particle sizes are high in cost, in order to reduce the cost, the second catalyst includes a carrier and an active substance supported on the carrier, the volume average particle size D50 of the carrier is greater than the volume average particle size D50 of the active substance, so that the second catalyst includes a composite catalyst, the active substance is supported on the carrier, the content of the active substance in the second catalyst is reduced while the volume of the catalyst is increased, and the cost is effectively reduced.

[0163] In a long-term water electrolysis process, the structure of the catalytic layer can collapse, which reduces the service life of the electrolytic cell, and the reason can be that the catalyst particles are damaged or fall off from the catalytic layer during the reaction, so that there are not enough catalyst particles in the catalytic layer to support the layered structure, and then the phenomenon of collapse of the catalytic layer occurs. The second catalyst in the application includes a carrier and an active substance supported on the carrier, the carrier can strengthen the support strength of the catalytic layer, reduce the problem of the active substance falling out of the catalytic layer, reduce the risk of collapse of the catalytic layer, and improve the service life of the electrolytic cell.

[0164] In an embodiment, the membrane electrode satisfies at least one of the following conditions: the volume average particle size D50 of the carrier ranges from 11 nm to 13 μm; the volume average particle size D50 of the active substance ranges from 0.1 nm to 500 nm; the loading content of the active substance in the second catalyst ranges from 0% to 60%; the carrier includes at least one of a first metal, a first metal oxide, porous carbon, and SiO2; the first metal includes at least one of Pt, Ti, Zr, and Al; and the ion exchange membrane includes a cation exchange membrane or an anion exchange membrane.

[0165] It can be understood that the volume average particle size D50 of the carrier ranges from 11 nm to 13 μm, which helps to build a trend that the porosity of the catalytic layer gradually increases from the direction close to the ion exchange membrane to the direction away from the ion exchange membrane, so as to help the generated bubbles to be discharged in time, release the active sites, and improve the mass transfer capacity of the membrane electrode.

[0166] The volume average particle size D50 of the active substance ranges from 0.1 nm to 500 nm, which satisfies the above range, and the active substance has a larger specific surface area, which helps to improve the catalytic active sites.

[0167] The loading content of the active substance in the second catalyst ranges from 0% to 60%, which satisfies the above range, and helps to reduce the cost while improving the catalytic performance.

[0168] The carrier comprises a first metal, a first metal oxide, porous carbon, SiO2; the first metal comprises at least one of Pt, Ti, Zr, Al, and it can be understood that the carrier has good electrical conductivity and porosity, which helps to improve the conduction of matter and electrons and improve the catalytic performance.

[0169] The ion exchange membrane comprises a cation exchange membrane or an anion exchange membrane, and a person skilled in the art can select the type of ion exchange membrane according to actual needs.

[0170] In the above 11nm to 13μm, the values include the minimum and maximum values of the range, and every value between such minimum and maximum values, and specific examples include but are not limited to the point values in the embodiments and 11nm, 20nm, 50nm, 100nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1μm, 5μm, 10μm, 13μm, etc., and the range values between any two point values.

[0171] In the above 0.1nm to 500nm, the values include the minimum and maximum values of the range, and every value between such minimum and maximum values, and specific examples include but are not limited to the point values in the embodiments and 0.5nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, etc., and the range values between any two point values.

[0172] In the above 0% to 60%, the values include the minimum and maximum values of the range, and every value between such minimum and maximum values, and specific examples include but are not limited to the point values in the embodiments and 0%, 0.1%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, etc., and the range values between any two point values.

[0173] In an embodiment, the membrane electrode satisfies at least one of the following conditions: the thickness of the first active layer is different from the thickness of the second active layer; the difference between the thickness of the first active layer and the thickness of the second active layer ranges from 1 μm to 24 μm; the thickness of the first active layer is less than the thickness of the second active layer; the thickness of the first active layer ranges from 0.01 μm to 23.01 μm; the thickness of the second active layer ranges from 1.01 μm to 24.01 μm; the catalytic layer comprises an anode catalytic layer and / or a cathode catalytic layer; the catalytic layer comprises an anode catalytic layer, the first catalyst and the second catalyst comprise at least one of iridium oxide, iridium black, iridium carbon, ruthenium iridium, platinum ruthenium iridium, a mixture of iridium and iridium oxide, a mixture of iridium oxide and titanium oxide; the catalytic layer comprises a cathode catalytic layer, the first catalyst and the second catalyst comprise at least one of a second metal and an alloy thereof; the second metal comprises at least one of Pt, Pd, Fe, Co, Ni; the material of the ion exchange membrane comprises at least one of a perfluorosulfonic acid ion polymer, a perfluorocarboxylic acid ion polymer, a composite membrane of a perfluorosulfonic acid ion polymer and a carbon nanotube, a composite membrane of a perfluorocarboxylic acid ion polymer and a carbon nanotube, a composite membrane of a perfluorosulfonic acid ion polymer and a metal oxide, a composite membrane of a perfluorocarboxylic acid ion polymer and a metal oxide; the mass percentage of the catalytically active substance in the first active layer is different from the mass percentage of the catalytically active substance in the second active layer; the mass percentage of the catalytically active substance in the first active layer is greater than the mass percentage of the catalytically active substance in the second active layer; the difference between the mass percentage of the catalytically active substance in the first active layer and the mass percentage of the catalytically active substance in the second active layer ranges from 5% to 100%; the mass percentage of the catalytically active substance in the first active layer ranges from 5% to 100%; the mass percentage of the catalytically active substance in the second active layer ranges from 0% to 70%.

[0174] In the present application, the thickness of the first active layer is different from the thickness of the second active layer, which means that the degree of oxygen evolution reaction is different in the entire catalytic layer, and the oxygen evolution reaction requires the supply of raw materials. The thickness of the adjacent two active layers is different, which can form a fast reaction zone and a raw material supply zone in the entire catalytic layer. It can be understood that in the adjacent two active layers, the gas generated in the layer with smaller thickness can quickly diffuse to the adjacent active layer, the reaction rate of this layer is increased, and the layer with larger thickness can provide uniform current distribution and sufficient reactant supply to provide raw materials for the adjacent layer with smaller thickness, which helps to improve the overall catalytic reaction rate.

[0175] In the present application, the difference between the thickness of the first active layer and the thickness of the second active layer ranges from 1 μm to 24 μm, which means that the above range is helpful for the rapid diffusion of gas and the improvement of reaction rate.

[0176] In the present application, the thickness of the first active layer is less than the thickness of the second active layer. It can be understood that the adjustment of the thickness can optimize the electrochemical reaction area, and by adjusting the thickness of the adjacent two active layers, the optimal reaction conditions can be provided in different areas. For example, in the reaction process of oxygen evolution, the first active layer close to the ion exchange membrane is the key reaction area, which requires a faster reaction rate. By making the thickness of the first active layer less than the thickness of the second active layer, the gas generated by the reaction in the first active layer can quickly diffuse to the adjacent layer, while the second active layer can provide uniform current distribution and sufficient reactant supply. In this way, the second active layer can provide raw materials for the first active layer to promote the rapid reaction of substances in the first active layer.

[0177] In the present application, the thickness of the first active layer ranges from 0.01 μm to 23.01 μm. It can be understood that meeting the above range is helpful for the rapid diffusion of gas and the provision of abundant active sites, thereby improving the catalytic performance.

[0178] In the present application, the thickness of the second active layer ranges from 1.01 μm to 24.01 μm. It can be understood that meeting the above range can provide the second active layer with uniform current distribution and sufficient reactant supply.

[0179] In the present application, the catalytic layer includes an anode catalytic layer and / or a cathode catalytic layer. It can be understood that the structure with a catalyst particle size gradient distribution from the direction close to the ion exchange membrane to the direction away from the ion exchange membrane can be an anode catalytic layer, can be a cathode catalytic layer, or can be an anode catalytic layer and a cathode catalytic layer, such as Figure 4 As shown in the figure, the ion exchange membrane is provided with an anode catalytic layer and a cathode catalytic layer on both sides.

[0180] In the present application, the catalytic layer includes an anode catalytic layer, and the first catalyst and the second catalyst include at least one of iridium oxide, iridium black, iridium carbon, ruthenium iridium, platinum ruthenium iridium, a mixture of iridium and iridium oxide, and a mixture of iridium oxide and titanium oxide.

[0181] In the present application, the catalytic layer includes a cathode catalytic layer, and the first catalyst and the second catalyst include at least one of a second metal and an alloy thereof, and the second metal includes at least one of Pt, Pd, Fe, Co, and Ni.

[0182] In the present application, the material of the ion exchange membrane includes at least one of a perfluorosulfonic acid ion polymer, a perfluorocarboxylic acid ion polymer, a composite membrane of a perfluorosulfonic acid ion polymer and a carbon nanotube, a composite membrane of a perfluorocarboxylic acid ion polymer and a carbon nanotube, a composite membrane of a perfluorosulfonic acid ion polymer and a metal oxide, and a composite membrane of a perfluorocarboxylic acid ion polymer and a metal oxide.

[0183] In the present application, the mass percentage of the catalytically active substance in the first active layer is different from the mass percentage of the catalytically active substance in the second active layer. Considering that the reaction rates of the two adjacent active layers are different, by setting different contents of catalytically active substances in different reaction rate regions, the utilization rate of the catalytically active substance can be improved, and the reaction efficiency can be improved. For example, high content of catalytically active substance is set in the region with high reaction rate, and low content of catalytically active substance is set in the region with low reaction rate.

[0184] In the present application, the mass percentage of the catalytically active substance in the first active layer is greater than the mass of the catalytically active substance in the second active layer, and the first active layer is closer to the ion exchange membrane than the second active layer. The first active layer is a key reaction region, and setting the mass percentage of the catalytically active substance in the first active layer to be greater than the mass of the catalytically active substance in the second active layer can help improve the reaction rate.

[0185] In the present application, the difference between the mass percentage of the catalytically active substance in the first active layer and the mass percentage of the catalytically active substance in the second active layer is in the range of 5% to 100%. It can be understood that meeting the above range can improve the reaction rate.

[0186] In the present application, the mass percentage of the catalytically active substance in the first active layer is in the range of 5% to 100%. It can be understood that meeting the above range can help provide abundant active sites and improve catalytic performance.

[0187] In the present application, the mass percentage of the catalytically active substance in the second active layer is in the range of 0% to 70%. It can be understood that meeting the above range can provide uniform current distribution and sufficient reactant supply in the second active layer.

[0188] In the above 1 μm to 24 μm, the values include the minimum and maximum values of the range, and every value between such minimum and maximum values, specific examples include but are not limited to point values in the embodiments and 1 μm, 5 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 22 μm, 24 μm, etc., and range values between any two of the above point values.

[0189] In the above 0.01 μm to 23.01 μm, the values include the minimum and maximum values of the range, and every value between such minimum and maximum values, specific examples include but are not limited to point values in the embodiments and 0.01 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1.0 μm, 5.0 μm, 10.0 μm, 13.0 μm, 15.0 μm, 18.0 μm, 20.0 μm, 22.0 μm, 23.01 μm, etc., and range values between any two of the above point values.

[0190] In the above 1.01 μm to 24.01 μm, the values include the minimum and maximum values of the range, and every value between the minimum and maximum values, and specific examples include but are not limited to the point values in the embodiments and 1.01 μm, 1.05 μm, 1.1 μm, 1.5 μm, 2.0 μm, 5.0 μm, 10.0 μm, 13.0 μm, 15.0 μm, 18.0 μm, 20.0 μm, 22.0 μm, 24.01 μm, etc., and the range values between any two point values.

[0191] In the above 5% to 100%, the values include the minimum and maximum values of the range, and every value between the minimum and maximum values, and specific examples include but are not limited to the point values in the embodiments and 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, etc., and the range values between any two point values.

[0192] In the above 0% to 100%, the values include the minimum and maximum values of the range, and every value between the minimum and maximum values, and specific examples include but are not limited to the point values in the embodiments and 0%, 0.1%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, etc., and the range values between any two point values.

[0193] In an embodiment, the application further provides a membrane electrode, comprising an ion exchange membrane and a catalytic layer arranged on at least one side of the ion exchange membrane, the catalytic layer comprising at least two active layers; defining two adjacent active layers as a first active layer and a second active layer; the first active layer is arranged on the ion exchange membrane, and the second active layer is arranged on the side of the first active layer away from the ion exchange membrane; the volume average particle size D50 of the first catalyst in the first active layer is smaller than the volume average particle size D50 of the second catalyst in the second active layer.

[0194] In an embodiment, the difference between the volume average particle size D50 of the first catalyst and the volume average particle size D50 of the second catalyst ranges from 1 nm to 10 μm.

[0195] In an embodiment, the volume average particle size D50 of the first catalyst ranges from 0.1 nm to 100 nm; and / or, the volume average particle size D50 of the second catalyst ranges from 11 nm to 13 μm.

[0196] In an embodiment, the at least two active layers are arranged in the order of A active layer and B active layer from the side close to the ion exchange membrane to the side away from the ion exchange membrane; the volume average particle size D50 of the catalyst in the A active layer ranges from 0.1 nm to 10 nm; and the volume average particle size D50 of the catalyst in the B active layer ranges from 11 nm to 50 nm.

[0197] In an embodiment, the second catalyst comprises a support and an active material supported on the support, the volume average particle size D50 of the support is greater than the volume average particle size D50 of the active material.

[0198] In an embodiment, the membrane electrode satisfies at least one of the following conditions: the volume average particle size D50 of the support ranges from 11 nm to 13 μm; the volume average particle size D50 of the active material ranges from 0.1 nm to 500 nm; the loading content of the active material in the second catalyst ranges from 0% to 60%; the support comprises at least one of the first metal, the first metal oxide, the porous carbon, and SiO2; the first metal comprises at least one of Pt, Ti, Zr, and Al; the ion exchange membrane comprises a cation exchange membrane or an anion exchange membrane.

[0199] In an embodiment, the membrane electrode satisfies at least one of the following conditions: the thickness of the first active layer is different from the thickness of the second active layer; the difference between the thickness of the first active layer and the thickness of the second active layer ranges from 1 μm to 24 μm; the thickness of the first active layer is less than the thickness of the second active layer; the thickness of the first active layer ranges from 0.01 μm to 23.01 μm; the thickness of the second active layer ranges from 1.01 μm to 24.01 μm; the catalytic layer comprises an anode catalytic layer and / or a cathode catalytic layer; the catalytic layer comprises an anode catalytic layer, and the first catalyst and the second catalyst comprise at least one of iridium oxide, iridium black, iridium carbon, ruthenium iridium, platinum ruthenium iridium, a mixture of iridium and iridium oxide, and a mixture of iridium oxide and titanium oxide; the catalytic layer comprises a cathode catalytic layer, and the first catalyst and the second catalyst comprise at least one of the second metal and an alloy thereof; the second metal comprises at least one of Pt, Pd, Fe, Co, and Ni; the material of the ion exchange membrane comprises at least one of a perfluorosulfonic acid ion polymer, a perfluorocarboxylic acid ion polymer, a composite membrane of the perfluorosulfonic acid ion polymer and carbon nanotubes, a composite membrane of the perfluorocarboxylic acid ion polymer and carbon nanotubes, a composite membrane of the perfluorosulfonic acid ion polymer and a metal oxide, and a composite membrane of the perfluorocarboxylic acid ion polymer and a metal oxide; the mass percentage of the catalytic active material in the first active layer is different from the mass percentage of the catalytic active material in the second active layer; the mass percentage of the catalytic active material in the first active layer is greater than the mass percentage of the catalytic active material in the second active layer; the difference between the mass percentage of the catalytic active material in the first active layer and the mass percentage of the catalytic active material in the second active layer ranges from 5% to 100%; the mass percentage of the catalytic active material in the first active layer ranges from 5% to 100%; and the mass percentage of the catalytic active material in the second active layer ranges from 0% to 70%.

[0200] In an embodiment, as Figure 6As shown, the application also provides a method for preparing a membrane electrode, comprising: coating at least two layers of active layer slurry on an ion exchange membrane, the volume average particle size D50 of the catalyst in the active layer arranged on the ion exchange membrane is less than the volume average particle size D50 of the catalyst in the active layer on the side away from the ion exchange membrane; and obtaining the membrane electrode after drying and cold pressing.

[0201] In the process of preparing the membrane electrode, the volume average particle size D50 of the catalyst in the active layer arranged on the ion exchange membrane is less than the volume average particle size D50 of the catalyst in the active layer on the side away from the ion exchange membrane by adjusting the volume average particle size D50 of the catalyst in the active layer slurry; in this way, the distribution of the gradient catalyst particles is designed, and the distribution of the gradient catalyst particles makes the porosity in the catalytic layer also have a gradient distribution, that is, the porosity in the catalytic layer gradually increases from the surface of the ion exchange membrane close to the ion exchange membrane to the surface of the ion exchange membrane away from the ion exchange membrane, which helps the generated bubbles to be discharged in time, releases the active sites, and improves the mass transfer capacity of the membrane electrode.

[0202] In an embodiment, in the step of coating the slurry of at least two layers of active layer on the ion exchange membrane, the step includes: mixing a first catalyst, a first ion polymer, a first additive, and a solvent to obtain a first active layer slurry; mixing a second catalyst, a second ion polymer, a second additive, and a solvent to obtain a second active layer slurry; coating the first active layer slurry on the surface of the ion exchange membrane to form a first active layer, and coating the second active layer slurry on the first active layer to form a second active layer.

[0203] In the step of coating the slurry of at least two layers of active layer on the ion exchange membrane, the step includes: mixing a first catalyst, a first ion polymer, a first additive, and a solvent to obtain a first active layer slurry; mixing a second catalyst, a second ion polymer, a second additive, and a solvent to obtain a second active layer slurry; coating the first active layer slurry on the surface of the ion exchange membrane to form a first active layer, and coating the second active layer slurry on the first active layer to form a second active layer.

[0204] In an embodiment, in the step of coating the first active layer slurry on the surface of the ion exchange membrane to form a first active layer, the coating method of the first active layer slurry includes any one of blade coating, spraying, blade coating transfer, and slot coating; and / or, in the step of coating the second active layer slurry on the first active layer to form a second active layer, the coating method of the second active layer slurry includes any one of blade coating, spraying, blade coating transfer, and slot coating.

[0205] Blade coating includes a coating method for making thick coating films by hand coating or automatic coating with a doctor blade.

[0206] Spraying is a coating method that disperses a uniform and fine mist by means of pressure or centrifugal force through a spray gun or an ultrasonic spraying device, and applies it to the surface of the coated object. The effect of spraying is better than that of doctor blading, and the stability of the catalyst and the uniformity of catalyst dispersion and the uniformity of the thickness of the catalyst layer are all better.

[0207] The doctor blading transfer method generally first applies the catalyst slurry to a transfer substrate (such as PTFE) by doctor blading, then combines it with the ion exchange membrane through a hot pressing process, and removes the transfer substrate to achieve the transfer of the catalyst from the transfer substrate to the ion exchange membrane. Generally speaking, the ion exchange membrane will form a relatively firm combination on the surface of the ion exchange membrane through the doctor blading transfer process, the stability of the catalyst layer is the best, the porosity is the smallest, and the density is the largest, but the process is relatively complex.

[0208] Slot coating is a coating technique that extrudes and transfers coating liquid along the gap of a mold to a moving substrate under a certain pressure

[0209] In the process of preparing the membrane electrode of the present application, any one of doctor blading, spraying, doctor blading transfer, and slot coating can be used in the coating process, and a suitable coating method can be selected as needed.

[0210] In an embodiment, the preparation method of the membrane electrode satisfies at least one of the following conditions: the difference between the volume average particle size D50 of the first catalyst and the volume average particle size D50 of the second catalyst ranges from 1 nm to 10 μm; the volume average particle size D50 of the first catalyst ranges from 0.1 nm to 100 nm; the volume average particle size D50 of the second catalyst ranges from 11 nm to 13 μm; the mass ratio of the first catalyst to the first ionomer ranges from 10:(2 to 80); the mass ratio of the second catalyst to the second ionomer ranges from 10:(2 to 80); the solvent includes at least one of isopropyl alcohol, methanol, ethanol, water, acetone, and tetrahydrofuran; the solid content of the first active layer slurry and the second active layer slurry ranges from 0.2% to 60%; the first active layer slurry and / or the second active layer slurry includes an additive, and the additive includes at least one of polytetrafluoroethylene, carboxymethyl cellulose, and polyperfluoroethylene propylene.

[0211] In the present application, the first active layer further includes a first ionomer, and the mass ratio of the first catalyst to the first ionomer ranges from 10:(2 to 80), which satisfies the above range, the first catalyst can be effectively dispersed in the first active layer, and the first active layer is effectively bonded to the ion exchange membrane.

[0212] In the present application, the second active layer further comprises a second ionomer, and the mass ratio of the second catalyst to the second ionomer ranges from 10:(2-80). When the mass ratio is within the above range, the second catalyst can be effectively dispersed in the second active layer, and the second active layer can be effectively bonded to the first active layer.

[0213] In the above range of 0.2% to 60%, the values include the minimum and maximum values of the range, and every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values in the embodiments, and 0.2%, 0.5%, 1%, 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, etc., and the range values between any two point values.

[0214] It can be understood that, in general, the higher the solid content of the catalyst slurry, the more densely the catalyst particles are distributed in the catalyst layer, and the smaller the voids. This is because the increase in solid content leads to more contact between catalyst particles, reducing the gap between particles. Therefore, a catalyst slurry with high solid content can form a more dense catalyst layer during spraying or coating. The voids of the catalyst layer also have an impact on the performance of the catalyst. Smaller voids can provide more active surface area, increasing the opportunity for contact between the catalyst and the reactants, thereby promoting reaction efficiency. In addition, smaller voids can also provide better proton transport channels. The solid content of the first active layer slurry and the second active layer slurry ranges from 0.2% to 60%, which can improve the catalytic performance.

[0215] The first active layer slurry and / or the second active layer slurry includes an additive, and the additive includes at least one of polytetrafluoroethylene, carboxymethyl cellulose, and polyperfluoroethylene propylene. The additive can enhance the adhesion effect of the active layer to the ion exchange membrane.

[0216] Embodiments

[0217] Embodiment 1

[0218] Preparation of membrane electrode

[0219] A first catalyst (anode catalyst) IrO2 with a D50 of 2 nm and a Nafion solution were dispersed in isopropyl alcohol at a mass ratio of 13:27, with a solid content of 30%. After mixing uniformly, a first active layer slurry was prepared. Then, the first active layer slurry was sprayed onto one side of a proton exchange membrane to form a proton exchange membrane loaded first active layer.

[0220] The second catalyst (anode catalyst) IrO2 with D50 of 50 nm and Nafion solution are dispersed in isopropyl alcohol as a solvent at a mass ratio of 13:27, and a solid content is 30%. After being uniformly mixed, a second active layer slurry is prepared. Then, the second active layer slurry is sprayed on the first active layer loaded on the proton exchange membrane to form a second active layer loaded on the proton exchange membrane. Two adjacent first active layers and second active layers are arranged on one side of the proton exchange membrane.

[0221] The cathode catalyst Pt / C and Nafion solution are dispersed in isopropyl alcohol as a solvent at a weight ratio of 1:2, and a cathode catalyst slurry is prepared after being uniformly mixed. Then, the cathode slurry is uniformly sprayed on the other side of the proton exchange membrane. After drying, transferring, hot pressing, and slitting, a gas diffusion layer is assembled to obtain a membrane electrode assembly.

[0222] Preparation of an electrolytic cell

[0223] The membrane electrode is assembled into a PEMWE electrolytic cell in the order of bipolar plate, sealing rubber ring, Teflon gasket, and membrane electrode. A torque wrench is used to assemble the single cell under the action of a nut, and the torque is set to 5 Nm. The single cell is assembled in the order of first diagonally and then along the edges. Then, the gas inlet and outlet are connected to the gas pipeline, and the working station is connected to obtain an electrolytic cell device.

[0224] Examples 2 to 5

[0225] On the basis of Example 1, the volume average particle size D50 of the first catalyst and the second catalyst is adjusted to obtain the data of Examples 2 to 5 in Example Table 1.

[0226] Example 6: The first catalyst (anode catalyst) IrO2 with D50 of 4 nm and Nafion solution are dispersed in isopropyl alcohol as a solvent at a mass ratio of 13:27, and a solid content is 30%. After being uniformly mixed, a first active layer slurry is prepared. Then, the first active layer slurry is once coated on a PTFE film by scraping. Through a hot pressing process, the first active layer loaded on the proton exchange membrane is transferred to one side of the proton exchange membrane at 100°C to 120°C (specifically 110°C) and a pressure in the range of 0.5 MPA to 3 MPA (specifically 1.5 MPA).

[0227] The second catalyst (anode catalyst) IrO2 with D50 of 20 nm and Nafion solution are dispersed in isopropyl alcohol as a solvent at a mass ratio of 13:27, and a solid content is 30%. After being uniformly mixed, a second active layer slurry is prepared. Then, the second active layer slurry is once coated on the first active layer loaded on the proton exchange membrane to form a second active layer loaded on the proton exchange membrane. Two adjacent first active layers and second active layers are arranged on one side of the proton exchange membrane.

[0228] Example 7: The first catalyst (anode catalyst) IrO2 with D50 of 4 nm, Nafion solution was dispersed in the solvent isopropyl alcohol according to the weight ratio of 13:27, with a solid content of 30%, and after mixing uniformly, the first active layer slurry was prepared; then the first active layer slurry was coated on the PTFE film once, and transferred to one side of the proton exchange membrane by hot pressing process at 110°C and pressure in the range of 1.5 MPA, to form the first active layer loaded on the proton exchange membrane;

[0229] The second catalyst (anode catalyst) IrO2 with D50 of 20 nm, Nafion solution was dispersed in the solvent isopropyl alcohol according to the mass ratio of 13:27, with a solid content of 1%, and after mixing uniformly, the second active layer slurry was prepared; then the second active layer slurry was sprayed on the first active layer loaded on the proton exchange membrane, to form the second active layer loaded on the proton exchange membrane; so that two adjacent first active layers and second active layers were arranged on one side of the proton exchange membrane.

[0230] Example 8: The first catalyst (anode catalyst) IrO2 with D50 of 4 nm, Nafion solution was dispersed in the solvent isopropyl alcohol according to the weight ratio of 13:27, with a solid content of 1%, and after mixing uniformly, the first active layer slurry was prepared; then the first active layer slurry was sprayed on one side of the proton exchange membrane, and after drying, the first active layer loaded on the proton exchange membrane was formed;

[0231] The second catalyst (anode catalyst) IrO2 with D50 of 20 nm, Nafion solution was dispersed in the solvent isopropyl alcohol according to the mass ratio of 13:27, with a solid content of 1%, and after mixing uniformly, the second active layer slurry was prepared; then the second active layer slurry was sprayed on the first active layer loaded on the proton exchange membrane, and after drying, the second active layer loaded on the proton exchange membrane was formed; so that two adjacent first active layers and second active layers were arranged on one side of the proton exchange membrane.

[0232] Example 9: On the basis of Example 1, the thickness of the two active layers was adjusted, and the data of Example 9 as described in Table 1 was obtained.

[0233] Example 10: On the basis of Example 1, the thickness of the two active layers was adjusted, and the data of Example 10 as described in Table 1 was obtained.

[0234] Comparative Example 1: On the basis of Example 5, the prepared first active layer slurry was coated on one side of the proton exchange membrane in one step, to form a catalytic layer with the same thickness as that of Example 5.

[0235] Comparative Example 2: On the basis of Example 5, a first catalyst with a D50 of 8 nm was mixed with a second catalyst with a D50 of 26 nm to prepare a first active layer slurry, which was coated on one side of a proton exchange membrane in one step to form a catalytic layer with the same thickness as that of Example 5.

[0236] Performance test

[0237] Transmission electron microscopy (TEM) test

[0238] The surface morphology and microstructure of the catalysts in all examples were analyzed by a transmission electron microscope (FEI Tecnai G2F20 S-TWIN) produced by the American FEI company, with a maximum acceleration voltage of 200 kV and a maximum magnification of 1,000,000 times. The TEM sample preparation method was as follows: a small amount of ground catalyst sample powder was taken in anhydrous ethanol, ultrasonic treatment was performed for 30 min to make it uniformly distributed to form a light gray dispersion liquid, a small amount of liquid was taken by a pipette and added dropwise on the front surface of a porous carbon carrier copper mesh, and then the copper mesh was naturally dried and placed in the instrument for testing. The D50 value was obtained by automatically counting the particle size distribution of the catalyst particles through image recognition.

[0239] Constant current stability test

[0240] The constant current stability electrolysis experiment was performed at a current density of 2 A / cm 2 , a constant current was applied to the membrane electrode, and the decay rate was obtained according to the fluctuation of the voltage curve to measure the stability of the membrane electrode.

[0241] Table 1 example list

[0242]

[0243]

[0244] As can be seen from Table 1, the decay rate of the voltage of the electrolytic cell prepared by using the examples with time is small, while the decay rate of the voltage of the electrolytic cell prepared by using the comparative examples with time is large, which indicates that the electrolytic cell of the examples is more stable.

[0245] That is, in the two adjacent active layers, the first active layer is closer to the proton exchange membrane than the second active layer, and the volume average particle size D50 of the first catalyst in the first active layer is smaller than the volume average particle size D50 of the second catalyst in the second active layer, so that the volume average particle size D50 of the catalyst in the catalytic layer on the surface of the proton exchange membrane gradually increases from the direction close to the proton exchange membrane to the direction away from the proton exchange membrane, which is beneficial to easily remove the generated bubbles during water electrolysis reaction, reduces the mass transfer resistance of the catalyst layer, optimizes the water electrolysis performance and reduces the energy consumption.

[0246] The above merely describes the preferred embodiments of the present application, and is not intended to limit the patent scope of the present application. Any equivalent structural changes made according to the content of the present application specification and drawings, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. An apparatus for electrolyzing water, characterized by comprising: The membrane electrode comprises a membrane electrode assembly, the membrane electrode assembly comprising an ion exchange membrane and a catalytic layer provided on at least one side of the ion exchange membrane, the catalytic layer comprising at least two active layers; The two adjacent active layers are defined as a first active layer and a second active layer; The first active layer is provided on the ion exchange membrane, and the second active layer is provided on the side of the first active layer away from the ion exchange membrane, the volume average particle size D50 of the first catalyst in the first active layer being smaller than the volume average particle size D50 of the second catalyst in the second active layer.

2. The water electrolysis device according to claim 1, wherein The difference between the volume average particle size D50 of the first catalyst and the volume average particle size D50 of the second catalyst ranges from 1 nm to 10 μm.

3. The water electrolysis device according to claim 1 or 2, wherein The volume average particle size D50 of the first catalyst ranges from 0.1 nm to 100 nm. And / or, the volume average particle size D50 of the second catalyst ranges from 11 nm to 13 μm.

4. The water electrolysis device according to any one of claims 1 to 3, wherein The at least two active layers are sequentially provided with an A active layer and a B active layer from the side close to the ion exchange membrane to the side away from the ion exchange membrane; The volume average particle size D50 of the catalyst in the A active layer ranges from 0.1 nm to 10 nm. The volume average particle size D50 of the catalyst in the B active layer ranges from 11 nm to 50 nm.

5. The water electrolysis device according to any one of claims 1 to 4, wherein The second catalyst comprises a carrier and an active substance supported on the carrier, the volume average particle size D50 of the carrier being greater than the volume average particle size D50 of the active substance.

6. The water electrolysis device according to claim 5, wherein At least one of the following conditions is met: The volume average particle size D50 of the carrier ranges from 11 nm to 13 μm. The volume average particle size D50 of the active substance ranges from 0.1 nm to 500 nm. The loading content of the active substance in the second catalyst ranges from 0% to 60%. The carrier comprises at least one of a first metal, a first metal oxide, porous carbon, and SiO2. The first metal comprises at least one of Pt, Ti, Zr, and Al. The ion exchange membrane comprises a cation exchange membrane or an anion exchange membrane.

7. The water electrolysis device according to any one of claims 1 to 6, wherein At least one of the following conditions is met: The thickness of the first active layer is different from the thickness of the second active layer. The difference between the thickness of the first active layer and the thickness of the second active layer ranges from 1 μm to 24 μm. The thickness of the first active layer is smaller than the thickness of the second active layer. The thickness of the first active layer ranges from 0.01 μm to 23.01 μm. The thickness of the second active layer ranges from 1.01 μm to 24.01 μm. The catalytic layer comprises an anode catalytic layer and / or a cathode catalytic layer. The catalytic layer comprises an anode catalytic layer, and the first catalyst and the second catalyst comprise at least one of iridium oxide, iridium black, iridium carbon, ruthenium iridium, platinum ruthenium iridium, a mixture of iridium and iridium oxide, and a mixture of iridium oxide and titanium oxide. The catalytic layer comprises a cathode catalytic layer, and the first catalyst and the second catalyst comprise at least one of a second metal and an alloy thereof. The second metal comprises at least one of Pt, Pd, Fe, Co, and Ni. The material of the ion exchange membrane includes at least one of a perfluorosulfonic acid ionomer, a perfluorocarboxylic acid ionomer, a composite membrane of a perfluorosulfonic acid ionomer and a carbon nanotube, a composite membrane of a perfluorocarboxylic acid ionomer and a carbon nanotube, a composite membrane of a perfluorosulfonic acid ionomer and a metal oxide, and a composite membrane of a perfluorocarboxylic acid ionomer and a metal oxide; The mass percentage of the catalytically active substance in the first active layer is different from the mass percentage of the catalytically active substance in the second active layer; The mass percentage of the catalytically active substance in the first active layer is greater than the mass percentage of the catalytically active substance in the second active layer; The difference between the mass percentage of the catalytically active substance in the first active layer and the mass percentage of the catalytically active substance in the second active layer ranges from 5% to 100%; The mass percentage of the catalytically active substance in the first active layer ranges from 5% to 100%; The mass percentage of the catalytically active substance in the second active layer ranges from 0% to 70%.

8. A membrane electrode characterized by, The catalytic layer includes at least two active layers; The two adjacent active layers are defined as a first active layer and a second active layer; The first active layer is arranged on the ion exchange membrane, and the second active layer is arranged on the side of the first active layer away from the ion exchange membrane, wherein the volume average particle size D50 of the first catalyst in the first active layer is smaller than the volume average particle size D50 of the second catalyst in the second active layer.

9. The membrane electrode of claim 8, wherein, The difference between the volume average particle size D50 of the first catalyst and the volume average particle size D50 of the second catalyst ranges from 1 nm to 10 μm.

10. The membrane electrode according to claim 8 or 9, characterized in that The volume average particle size D50 of the first catalyst ranges from 0.1 nm to 100 nm. The volume average particle size D50 of the second catalyst ranges from 11 nm to 13 μm.

11. The membrane electrode according to any one of claims 8 to 10, wherein The at least two active layers are arranged in the order of an A active layer and a B active layer from the side close to the ion exchange membrane to the side away from the ion exchange membrane; The volume average particle size D50 of the catalyst in the A active layer ranges from 0.1 nm to 10 nm. The volume average particle size D50 of the catalyst in the B active layer ranges from 11 nm to 50 nm.

12. The membrane electrode of any one of claims 8 to 11, wherein, The second catalyst includes a carrier and an active substance supported on the carrier, wherein the volume average particle size D50 of the carrier is greater than the volume average particle size D50 of the active substance.

13. The membrane electrode of claim 12, wherein, At least one of the following conditions is met: The volume average particle size D50 of the carrier ranges from 11 nm to 13 μm. The volume average particle size D50 of the active substance ranges from 0.1 nm to 500 nm. The loading content of the active substance in the second catalyst ranges from 0% to 60%. The carrier includes at least one of a first metal, a first metal oxide, porous carbon, and SiO2. The first metal includes at least one of Pt, Ti, Zr, and Al. The ion exchange membrane includes a cation exchange membrane or an anion exchange membrane.

14. The membrane electrode of any one of claims 8 to 13, wherein, At least one of the following conditions is met: The thickness of the first active layer is different from the thickness of the second active layer; The difference between the thickness of the first active layer and the thickness of the second active layer ranges from 1 μm to 24 μm; The thickness of the first active layer is less than the thickness of the second active layer; The thickness of the first active layer ranges from 0.01 μm to 23.01 μm; The thickness of the second active layer ranges from 1.01 μm to 24.01 μm; The catalytic layer comprises an anode catalytic layer and / or a cathode catalytic layer; The catalytic layer comprises an anode catalytic layer, and the first catalyst and the second catalyst comprise at least one of iridium oxide, iridium black, iridium carbon, ruthenium iridium, platinum ruthenium iridium, a mixture of iridium and iridium oxide, and a mixture of iridium oxide and titanium oxide; The catalytic layer comprises a cathode catalytic layer, and the first catalyst and the second catalyst comprise at least one of a second metal and an alloy thereof; The second metal comprises at least one of Pt, Pd, Fe, Co, and Ni; The material of the ion exchange membrane comprises at least one of a perfluorosulfonic acid ion polymer, a perfluorocarboxylic acid ion polymer, a composite membrane of a perfluorosulfonic acid ion polymer and a carbon nanotube, a composite membrane of a perfluorocarboxylic acid ion polymer and a carbon nanotube, a composite membrane of a perfluorosulfonic acid ion polymer and a metal oxide, and a composite membrane of a perfluorocarboxylic acid ion polymer and a metal oxide; The mass percentage of the catalytically active substance in the first active layer is different from the mass percentage of the catalytically active substance in the second active layer; The mass percentage of the catalytically active substance in the first active layer is greater than the mass percentage of the catalytically active substance in the second active layer; The difference between the mass percentage of the catalytically active substance in the first active layer and the mass percentage of the catalytically active substance in the second active layer ranges from 5% to 100%; The mass percentage of the catalytically active substance in the first active layer ranges from 5% to 100%; The mass percentage of the catalytically active substance in the second active layer ranges from 0% to 70%.

15. The method for producing a membrane electrode according to any one of claims 1 to 14, wherein Comprising: A step of coating at least two layers of active layer slurry on the ion exchange membrane, the volume average particle size D50 of the catalyst in one layer of active layer arranged on the ion exchange membrane is less than the volume average particle size D50 of the catalyst in one layer of active layer away from the ion exchange membrane; After drying and cold pressing, a membrane electrode is obtained.

16. The method for producing a membrane electrode as claimed in claim 15, wherein The step of coating at least two layers of active layer slurry on the ion exchange membrane comprises: Mixing a first catalyst, a first ion polymer, and a solvent to obtain a first active layer slurry; Mixing a second catalyst, a second ion polymer, and a solvent to obtain a second active layer slurry; Coating the first active layer slurry on the surface of the ion exchange membrane to form a first active layer, and coating the second active layer slurry on the first active layer to form a second active layer.

17. The method of claim 16, wherein the membrane electrode is prepared by In the step of coating the first active layer slurry on the surface of the ion exchange membrane to form a first active layer, the coating method of the first active layer slurry comprises any one of blade coating, spraying, blade coating transfer, and slot coating. And / or, in the step of forming the second active layer by coating the second active layer slurry on the first active layer, the coating method of the second active layer slurry includes any one of the following: doctor blade coating, spray coating, doctor blade transfer printing, and slot coating.

18. The method for producing a membrane electrode according to any one of claims 15 to 17, wherein At least one of the following conditions is satisfied: The difference between the volume average particle size D50 of the first catalyst and the volume average particle size D50 of the second catalyst is in the range of 1 nm to 10 μm; The volume average particle size D50 of the first catalyst is in the range of 0.1 nm to 100 nm; The volume average particle size D50 of the second catalyst is in the range of 11 nm to 13 μm; The mass ratio of the first catalyst to the first ionic polymer is in the range of 10:(2 to 80); The mass ratio of the second catalyst to the second ionic polymer is in the range of 10:(2 to 80); The solvent includes at least one of the following: isopropyl alcohol, methanol, ethanol, water, acetone, and tetrahydrofuran; The solid content of the first active layer slurry and the second active layer slurry is in the range of 0.2% to 60%; The first active layer slurry and / or the second active layer slurry includes an additive, and the additive includes at least one of the following: polytetrafluoroethylene, carboxymethyl cellulose, and polyperfluoroethylene propylene.

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