RU2456717C1 - Method of forming catalyst layer for solid-polymer fuel cell - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of forming a catalyst layer for a solid-polymer fuel cell involves treatment of multi-wall carbon nanotubes with gaseous plasma in the medium of an inorganic gas or a mixture of inorganic gases at electric discharge frequency 13-40 MHz, electric discharge power 0.01-0.1 W/cm³ and pressure 0.20-1.13 torr for 300-500 s. The multi-wall carbon nanotubes treated with gaseous plasma are treated with concentrated nitric acid at temperature 100-120°C for 5-10 min. The obtained suspension is cooled. Multi-wall carbon nanotubes are filtered therefrom, washed and dried. Further, the dried multi-wall carbon nanotubes are mixed with platinised carbon black containing 20-40 wt % platinum, isopropanol and aqueous nafion solution, taken in a defined ratio. The obtained suspension is treated with ultrasound for 30-60 min and then sputtered onto a perfluorinated sulphopolymer-based proton-conducting membrane which is heated to temperature 70-90°C.

EFFECT: high specific power due to high efficiency of catalysis.

4 cl, 3 dwg, 6 ex

Description

The entry of solid polymer fuel cells (TPTE) into the mass consumption market requires the creation of effective technologies to increase their efficiency and reduce the cost of final products. Catalytic layers are one of the most important components of TPTE, the efficiency of the fuel cell (FC) as a whole depends on the quality of their work. Important parameters of the operation of the catalytic layers include maximum specific power and platinum loading. High specific power allows to reduce the weight and size parameters of TPTE, while reducing the load of platinum allows to reduce the cost of the product and allows you to deploy mass production. It is known (see S. A. Gurevich, M. V. Gorokhov, N. K. Zelenina, V. M. Kozhevin, E. E. Terukova, A. A. Tomasov. - Optimization of membrane-electrode blocks based on polymer electrolyte membranes for fuel cells. - Letters to ZhTF, 2009, volume 35, issue 20) that a simple increase in the loading of platinum allows increasing the specific power of the membrane-electrode block (OIE) only to certain limits, then the diffusion limitations of the layer and a number of other factors limiting the growth of specific power. An increase in the specific power removed from the catalytic layer without increasing the loading of platinum is possible due to the formation of catalytic layers with increased catalysis efficiency. The catalytic layers with increased catalysis efficiency are carried out both by selecting the appropriate catalyst composition and by creating the optimal structure of the catalytic layer.

A known method of forming a catalytic layer of a fuel cell (see patent RU No. 2414021, IPC H01M 4/88, published 03/10/2011), in accordance with which platinum oxide or platinum group metal oxide is sprayed onto the surface of the catalyst base of the initial film. The film is irradiated in a vacuum with a beam of accelerated particles from hydrogen atoms or ions with the energy necessary for the selective removal of oxygen atoms from the entire thickness of the deposited source oxide and the formation of a platinum film or platinum group metal with specified electrophysical parameters. In this case, the projective path length of accelerated ions or hydrogen atoms in the reduced metal film and the dose dependence of the change in the electrical resistance of the initial oxide film to specified values indicating the formation of a metal with specified values of electrophysical parameters are experimentally determined previously. Based on the obtained dependences, the fluence of accelerated particles is prescribed, and the thickness of the initial film is chosen no more than the projective range of accelerated particles in the reduced metal film.

The known method requires the use of expensive equipment, which complicates the technology and significantly increases the cost of the catalytic layer. The need for preliminary measurements of the mean free path of accelerated ions or hydrogen atoms in the film of the reduced metal increases the production time of the catalytic layer.

A known method of forming a membrane-electrode block with a porous cathode (see patent RU No. 2015207, IPC C25B 11/20, published on 06/30/1994). The method includes preparing a mixture of electrocatalytic particles with a binder, applying the mixture to a membrane, drying and sintering. An aluminum powder is further added to the mixture. After sintering, the membrane-electrode block is leached.

Thanks to this technique, the aluminum phase dissolves, leaving pores in its place. As a result, the porosity of the layer increases and the diffusion resistance decreases. The disadvantages of this method is that this method is aimed only at reducing the diffusion resistance of the layer, it does not affect the catalytic activity of the catalyst and, therefore, is not so effective. In addition, the known method is quite laborious and requires thorough washing after leaching of aluminum from its ions.

A known method of forming a catalytic layer of a fuel cell (see patent RU No. 2358359, IPC H01M 4/88, published 10.06.2009), including magnetron sputtering on a substrate simultaneously of platinum and carbon, impregnation of the obtained nanocomposite layer of amorphous carbon and platinum with silicophosphate sol and the subsequent drying the formed porous gel layer. Carbon is deposited on a substrate by magnetron sputtering of a graphite target. As the substrate, a polymer with proton conductivity, for example, a polyaniline film obtained by aniline oxidative polymerization, can be used.

The disadvantages of this method are the possibility of forming only relatively thin layers, which does not allow to achieve high specific power.

A known method of forming a catalytic layer of TPTE (see PCT application WO No.2010051637, IPC H01M 4/88; H01M 4/90, published 05/14/2010), including the deposition of metals selected from the group: platinum, an alloy of platinum with transition metals, mixtures thereof base metals. The catalytic layer contains particles from 1 nm to 15 nm and clusters of these particles.

The known method involves the use of non-platinum group metals, which is associated with the danger of their dissolution during operation of the catalytic layer and blocking of the proton-conducting centers of the proton-conducting component of the layer. At the same time, due to a decrease in proton conductivity, the catalyst use efficiency and specific power will decrease.

A known method for the manufacture of catalytic layers with high electrical conductivity (see application US No. 20090130527, IPC H01M 4/88, published 05/21/2009), comprising applying particles of graphite, carbon nanotubes and corrosion-resistant metals to a solid polymer electrolyte. The method allows to increase the electrical conductivity of the catalytic layers by increasing the electronic conductivity.

The disadvantage of this method is that the proton conductivity, which equally determines the efficiency of the fuel cell, remains unchanged. In addition, the contribution of the electrical conductivity of the catalytic layers to the total series conductivity of the fuel cell is not so large and the technique used in the patent cannot give a large increase in the efficiency of the fuel cell.

A known method of manufacturing the catalytic layers of membrane-electrode blocks (see S. A. Gurevich, M. V. Gorokhov, N. K. Zelenin, V. M. Kozhevin, E. E. Terukova, A. A. Tomasov. Membrane optimization -electrode blocks based on polymer-electrolyte membranes for fuel cells. Letters to ZhTF, 2009, volume 35, issue 20), which uses the method of adding carbon nanotubes (CNTs) to a mixture (catalytic ink) used to prepare catalytic layers. The role of CNTs in this case is to create a certain loose structure with a relatively small diffusion resistance.

The disadvantage of this method is that non-functionalized CNTs are used, which does not allow using the effect of socialization and limits the increase in the efficiency of platinum use.

A known method of forming a catalytic layer of a solid polymer fuel cell (see US patent No. 7220693, IPC H01M 4/88, published 05/22/2007), coinciding with the claimed solution for the largest number of essential features and adopted for the prototype. The prototype method includes preparing a carbon catalyst carrier, mixing the carbon catalyst carrier with a proton-conducting material, manufacturing an element containing an active layer from a mixture of a carbon catalyst carrier with a proton-conducting material, direct sulfonation of the element with a sulfonating agent, including inorganic salts. In the prototype method, acidic, proton-conducting sulfo groups are attached directly to the surface of the carbon material. Moreover, due to the proximity of the acid groups themselves and the particles of the metal catalyst, the efficiency of using the catalyst surface increases, which is not achieved using only Nafion.

However, the prototype method only improves the interfacial contact area between the catalyst, proton conductor, electronic conductor and reagent.

The objective of the present invention was to develop a method of forming a catalytic layer of a solid polymer fuel cell, which would not require the use of complex technology, and when using the catalyst layer made in this way in membrane-electrode blocks of solid polymer fuel cells, providing increased specific power by increasing the efficiency of catalysis, with a slight change cost.

The problem is solved in that the method of forming a catalytic layer of a solid polymer fuel cell includes the processing of multi-walled carbon nanotubes with gas plasma in an inorganic gas medium or a mixture of inorganic gases at an electric discharge frequency of 13-40 MHz, electric discharge power of 0.01-0.1 W / cm ³ and a pressure of 0.20-1.13 Torr for 300-500 seconds. Then, multi-walled carbon nanotubes are treated with concentrated nitric acid at a temperature of 100-120 ° C for 5-10 minutes, the resulting first suspension is cooled to room temperature, multi-walled carbon nanotubes are filtered off from it, washed with distilled water and dried at room temperature. The dried multi-walled carbon nanotubes are mixed with platinized carbon black containing 20-40 wt.% Platinum, isopropanol and an aqueous Nafion solution, calculated on the dry matter in the ratio, wt.%:

multi-walled carbon nanotubes 0.15-1.8 platinum carbon black 1,5-4,5 nafion 0.44-1.20 isopropanol 94-98.

The resulting second suspension is treated with ultrasound for 30-60 minutes and then the second suspension is sprayed onto a proton-conducting membrane based on a perfluorinated sulfopolymer heated to a temperature of 70-90 ° C.

Naphion is preferably used as the perfluorinated sulfopolymer.

The second suspension can be sprayed with an airbrush through a metal mask with an opening equal to the specified size of the catalytic layer.

As an inorganic gas, you can use a gas selected from the group: nitrogen, argon, carbon dioxide, oxygen and mixtures thereof.

The choice of intervals for the content of the components of the second suspension is due to the fact that when the content of multi-walled carbon nanotubes is less than 0.15 wt.%, The effect of their presence becomes invisible, that is, with such a small content of CNTs, there is no noticeable increase in the efficiency of use of platinum and an increase in specific power, and when content of more than 1.8 wt.% due to a decrease in the concentration of platinum in the catalytic layer there is no significant increase in specific power, when the content of platinum carbon black is less than 1.5 wt.% there is no noticeable increase in specific power, and with a content of more than 4.5 wt.% there is no noticeable increase in the efficiency of use of platinum and an increase in specific power, when the Nafion content is less than 0.44 wt.%, the proton conductivity of the catalytic layer is strongly as a result, the specific power and efficiency of platinum use decreases, and when the content is more than 1.20 wt.%, Nafion blocks a significant part of the platinum surface, as a result of which the specific power decreases and the effective the use of platinum, when the content of isopropanol is less than 94 wt.%, it is difficult to spray a uniform layer by increasing the density of the dispersion, and if it contains more than 98 wt.%, the likelihood of dissolution of the membrane and violation of the integrity and its gas-insulating properties increases, resulting in a significant drop in voltage and power . Multi-walled carbon nanotubes were chosen because they have the ability to functionalize — to attach functional groups as opposed to single-walled carbon nanotubes, which are destroyed by attempts to functionalize. If platinum carbon black contains less than 20 wt.% Platinum, the specific power decreases due to a small amount of platinum, and when it contains more than 40 wt.% Platinum, the efficiency of platinum is reduced, that is, to achieve the same specific power, more platinum is required. The present technical solution consists in the formation of a catalytic layer of a solid polymer fuel cell from catalytic inks containing multi-walled carbon nanotubes sequentially subjected to plasma-chemical treatment in order to open the ends and chemical functionalization for joining oxygen-containing functional groups. The method provides for the simultaneous formation of catalytic layers, improved in structure, catalytic activity, electronic conductivity and surface utilization of the metal catalyst - platinum. A decrease in the diffusion resistance of the layer occurs due to loosening of it by multi-walled carbon nanotubes. The multi-walled CNTs themselves, after plasma chemical treatment and chemical functionalization, acquire the ability to enhance electrocatalysis on platinum in relation to the oxygen electroreduction reaction. In addition, oxygen-containing acidic functional groups (for example, carboxyl) have the ability to exchange protons, thereby increasing the efficiency of proton transport during the operation of the catalytic layer. The method also allows to increase the catalytic activity and efficiency of platinum use due to the phenomenon of socialization on functionalized multi-walled CNTs (FMSCNTs), resulting in the formation of catalytic layers with increased specific power at the same platinum load.

The present invention is illustrated by drawings, where:

figure 1 shows the discharge and power curves of air-hydrogen fuel cells with a platinum-containing catalyst of type E-TEK without functionalized CNTs;

figure 2 shows the discharge and power curves of air-hydrogen TE with the catalyst E-TEK + FMSUNT taken in a mass ratio of 1: 1;

figure 3 in the table gives a summary of the performance of the catalytic layers made with the addition of functionalized carbon nanotubes.

A method of forming a catalytic layer of a solid polymer fuel cell is as follows. The method consists of the following successive stages: plasma-chemical treatment of multi-walled CNTs, chemical functionalization of multi-walled CNTs, preparation of catalytic ink, the formation of CS. Plasma-chemical processing consists in treating multi-walled CNTs with a gas plasma in an inorganic gas or inorganic gas mixture at an electric discharge frequency in the range of 13-40 MHz with an electric discharge power of 0.01-0.1 W / cm ³ and an inorganic gas pressure or inorganic gas mixture in the range of 0.2-1.13 Torr for 300-500 s. As an inorganic gas, you can use a gas selected from the group: nitrogen, argon, carbon dioxide, oxygen and mixtures thereof. Chemical functionalization consists in treating CNTs in concentrated nitric acid at a temperature of 100-120 ° C for 5-10 minutes, followed by washing multi-walled CNTs with distilled water and air drying. Catalytic ink is prepared by mixing platinum carbon black containing 20-40 wt.% Platinum, processed in a gas plasma of carbon nanotubes and an aqueous solution of Nafion and isopropanol, calculated on the dry matter in the ratio, wt.%:

multi-walled carbon nanotubes 0.15-1.8 platinum carbon black 1,5-4,5 nafion 0.44-1.20 isopropanol 94-98.

The resulting second suspension is treated with ultrasound for 30-60 minutes. The catalytic layers are formed by sputtering a second suspension onto a proton-conducting membrane heated to a temperature of 70-90 ° C based on a perfluorinated sulfopolymer, which can be taken as a nafion. Spraying can be carried out by airbrushing through a metal mask with an opening equal to the specified size of the catalytic layer.

The catalytic layer for TE obtained by this method has a high surface electrocatalytic activity of platinum due to its high dispersion, degree of utilization of the platinum surface and cocatalization by functionalized carbon nanotubes, which makes it possible to increase the efficiency of electrocatalysis by ensuring good diffusion of reagents to the phase separation region: electron-conducting, proton-conducting, and active the beginning of the catalyst, as well as due to the higher catalytic activity of the material.

Example 1. Sample ADK-5

Multi-walled CNTs were placed in a technological chamber of a plasma-chemical treatment installation on a tray (layer thickness of about 0.45 mm). A plasma discharge was created in a CO ₂ medium at a residual pressure of 0.5 Torr, a specific electric discharge power of 0.1 W / cm ³ and a frequency of 13 MHz. Processing was carried out for 400 s. 105 mg of the resulting plasma treatment material was placed in a glass beaker with a capacity of 250 cm ³ , 100 cm ^{3 of} concentrated nitric acid was added and heated to boiling on an electric stove. The mixture was kept under heating for 6 minutes, after which it was removed from the tile and cooled to room temperature. CNTs were filtered through a dense filter (“green tape” brand) and washed 5 times with distilled water. Multiwall CNTs were air dried 12 hours. In a test tube with a cap with a capacity of 10 cm ³ were placed: 0.005 g of multi-walled CNTs; 0.075 g platinum carbon black (E-TEK with 20 wt.% Pt); 0.20 g of a 10% aqueous solution of Nafion; 1.57 g of isopropanol. The tube was closed with a lid and placed in an ultrasonic bath for 60 minutes (ultrasound frequency 40 kHz). During ultrasonic treatment, the temperature in the bath was maintained at ~ 25 ° C. The resulting catalytic ink was placed in an airbrush chamber. A proton-conducting membrane of the nafion 212 type with a size of 40 × 40 mm ^{2 was} placed on a surface with a controlled temperature of 80 ° C, covered with a stainless steel mask with a window of 10 × 10 mm ² and held for 3 minutes for heating. After that, the airbrush compressor was turned on and ~ 1 cm ³ was sprayed onto the first surface of the membrane. Then, the membrane was turned over, covered with a mask, and the remaining catalytic ink was sprayed onto the second surface of the membrane (~ 1 cm ³ ).

Example 2. Sample ATK-11

Multi-walled CNTs were placed in a technological chamber of a plasma-chemical treatment installation on a tray (layer thickness of about 0.45 mm). A plasma discharge was created in an Ar medium at a residual pressure of 1.1 Torr, a specific electric discharge power of 0.07 W / cm ³ and a frequency of 40 MHz. Processing was carried out for 500 s. 50 mg of multi-walled CNTs obtained by plasma treatment were placed in a glass beaker with a capacity of 250 cm ³ , 100 cm ^{3 of} concentrated nitric acid was added and heated to boiling on an electric stove. The mixture was kept under heating for 10 minutes, after which it was removed from the tile and cooled to room temperature. Multi-walled CNTs were filtered through a dense filter (“green tape” brand) and washed 5 times with distilled water. Multiwall CNTs were air dried 12 hours. In a test tube with a cap with a capacity of 10 cm ³ were placed: 0,0072 mg of multi-walled CNTs; 0.072 g platinum carbon black (E-TEK with 20 wt.% Pt); 0.21 g of a 10% aqueous solution of Nafion; 4.71 g of isopropanol. The tube was closed with a lid and placed in an ultrasonic bath for 60 minutes (ultrasound frequency 40 kHz). During ultrasonic treatment, the temperature in the bath was maintained at ~ 23 ° C. The resulting catalytic ink was placed in an airbrush chamber. A proton-conducting membrane of the nafion 212 type with a size of 40 × 40 mm ^{2 was} placed on a surface with a controlled temperature of 80 ° C, covered with a stainless steel mask with a window of 15 × 15 mm ² and kept for 5 minutes for heating. After that, the airbrush compressor was turned on and ~ 1 cm ³ was sprayed onto the first surface of the membrane. Then, the membrane was turned over, covered with a mask, and the remaining catalytic ink was sprayed onto the second surface of the membrane (~ 1 cm ³ ).

Example 3. Sample ATK-14

Multi-walled CNTs were placed in a technological chamber of a plasma-chemical treatment installation on a tray (layer thickness of about 0.45 mm). A plasma discharge was created in an Ar + O ₂ + N ₂ medium in equal parts at a residual pressure of 0.5 Torr, a specific electric discharge power of 0.05 W / cm ³ and a frequency of 40 MHz. Processing was carried out for 450 s. 100 mg of the resulting plasma treatment material was placed in a glass beaker with a capacity of 250 cm ³ , 100 cm ^{3 of} concentrated nitric acid was added and heated to boiling on an electric stove. The mixture was kept under heating for 10 minutes, after which it was removed from the tile and cooled to room temperature. Multi-walled CNTs were filtered through a dense filter (“green tape” brand) and washed 5 times with distilled water. CNTs were air dried for 12 hours. In a test tube with a cap with a capacity of 10 cm ³ were placed: 0.011 g of multi-walled CNTs; 0.069 g of platinum carbon black (E-TEK with 20 wt.% Pt); 0.20 g of a 10% aqueous solution of Nafion; 2.36 g of isopropanol. The tube was closed with a lid and placed in an ultrasonic bath for 60 minutes (ultrasound frequency 40 kHz). During ultrasonic treatment, the temperature in the bath was maintained at ~ 25 ° C. The resulting catalytic ink was placed in an airbrush chamber. A 40 × 40 mm ² proton-conducting membrane of nafion 212 type was placed on a surface with a controlled temperature of 90 ° С, covered with a stainless steel mask with a window of 10 × 10 mm ^2, and held for 2 minutes for heating. After that, the airbrush compressor was turned on and ~ 0.7 cm ³ was sprayed onto the first surface of the membrane. Then, the membrane was turned over, covered with a mask, and the remaining catalytic ink was sprayed onto the second surface of the membrane (~ 1.3 cm ³ ).

Example 4. Sample ADK-3

Multi-walled CNTs were placed in a technological chamber of a plasma-chemical treatment installation on a tray (layer thickness of about 0.45 mm). A plasma discharge was created in an Ar + O ₂ + N ₂ medium in equal parts at a residual pressure of 0.5 Torr, a specific electric discharge power of 0.05 W / cm ³ and a frequency of 40 MHz. Processing was carried out for 450 s. 100 mg of multi-walled CNTs obtained by plasma treatment were placed in a glass beaker with a capacity of 250 cm ³ , 100 cm ^{3 of} concentrated nitric acid was added and heated to boiling on an electric stove. The mixture was kept under heating for 10 minutes, after which it was removed from the tile and cooled to room temperature. CNTs were filtered through a dense filter (“green tape” brand) and washed 5 times with distilled water. CNTs were air dried for 12 hours. In a test tube with a cap with a capacity of 10 cm ³ were placed: 0.022 g of CNT; 0.056 g of platinum carbon black (E-TEK with 20 wt.% Pt); 0.20 g of a 10% aqueous solution of Nafion; 1.57 g of isopropanol. The tube was closed with a lid and placed in an ultrasonic bath for 60 minutes (ultrasound frequency 40 kHz). During ultrasonic treatment, the temperature in the bath was maintained at ~ 23 ° C. The resulting catalytic ink was placed in an airbrush chamber. A proton-conducting membrane of the nafion 212 type with a size of 40 × 40 mm ^{2 was} placed on a surface with a controlled temperature of 80 ° C, covered with a stainless steel mask with a window of 10 × 10 mm ² and held for 3 minutes for heating. After that, the airbrush compressor was turned on and ~ 1 cm ³ was sprayed onto the first surface of the membrane. Then, the membrane was turned over, covered with a mask, and the remaining catalytic ink was sprayed onto the second surface of the membrane (~ 1 cm ³ ).

Example 5. Sample ADK-2

Multi-walled CNTs were placed in a technological chamber of a plasma-chemical treatment installation on a tray (layer thickness of about 0.45 mm). A plasma discharge was created in an Ar + O ₂ + N ₂ medium in equal parts at a residual pressure of 0.5 Torr, a specific electric discharge power of 0.05 W / cm ³ and a frequency of 40 MHz. Processing was carried out for 450 s. 100 mg of multi-walled CNTs obtained by plasma treatment were placed in a glass beaker with a capacity of 250 cm ³ , 100 cm ^{3 of} concentrated nitric acid was added and heated to boiling on an electric stove. The mixture was kept under heating for 10 minutes, after which it was removed from the tile and cooled to room temperature. CNTs were filtered through a dense filter (“green tape” brand) and washed 5 times with distilled water. Multiwall CNTs were air dried 12 hours. In a test tube with a cap with a capacity of 10 cm ³ were placed: 0.038 g of multi-walled CNTs; 0.038 g platinum carbon black (E-TEK with 20 wt.% Pt); 0.25 g of a 10% aqueous solution of Nafion; 1.96 g of isopropanol. The tube was closed with a lid and placed in an ultrasonic bath for 60 minutes (ultrasound frequency 40 kHz). During ultrasonic treatment, the temperature in the bath was maintained at ~ 22 ° C. The resulting catalytic ink was placed in an airbrush chamber. A nafion 212 proton-conducting membrane of 40 × 40 mm ² type was placed on a surface with a controlled temperature of 70 ° C, covered with a stainless steel mask with a 23 × 23 mm ² window, and held for 3 minutes for heating. After that, the airbrush compressor was turned on and ~ 1 cm ³ was sprayed onto the first surface of the membrane. Then, the membrane was turned over, covered with a mask, and the remaining catalytic ink was sprayed onto the second surface of the membrane (~ 1 cm ³ ).

Example 6. Sample ADK-1

Multi-walled CNTs were placed in a technological chamber of a plasma-chemical treatment installation on a tray (layer thickness of about 0.45 mm). A plasma discharge was created in an Ar + O ₂ + N ₂ medium in equal proportions at a residual pressure of 0.5 Torr, a specific electric discharge power of 0.05 W / cm ³ and a frequency of 40 MHz. Processing was carried out for 450 s. 100 mg of multi-walled CNTs obtained by plasma treatment were placed in a glass beaker with a capacity of 250 cm ³ , 100 cm ^{3 of} concentrated nitric acid was added and heated to boiling on an electric stove. The mixture was kept under heating for 10 minutes, after which it was removed from the tile and cooled to room temperature. CNTs were filtered through a dense filter (“green tape” brand) and washed 5 times with distilled water. Multiwall CNTs were air dried 12 hours. In a test tube with a cap with a capacity of 10 cm ³ were placed: 0.038 g of multi-walled CNTs; 0.038 g platinum carbon black (E-TEK with 40 wt.% Pt); 0.25 g of a 10% aqueous solution of Nafion; 1.96 g of isopropanol. The tube was closed with a lid and placed in an ultrasonic bath for 60 minutes (ultrasound frequency 40 kHz). During ultrasonic treatment, the temperature in the bath was maintained at ~ 22 ° C. The resulting catalytic ink was placed in an airbrush chamber. A nafion 212 proton-conducting membrane of 40 × 40 mm ² type was placed on a surface with a controlled temperature of 70 ° C, covered with a stainless steel mask with a 23 × 23 mm ² window, and held for 3 minutes for heating. After that, the airbrush compressor was turned on and ~ 0.5 cm ³ was sprayed onto the first surface of the membrane. Then, the membrane was turned over, covered with a mask, and catalytic ink was sprayed onto the second surface of the membrane (~ 0.5 cm ³ ).

A summary of the performance of the catalytic layers made with the addition of functionalized multi-walled carbon nanotubes is shown in the table in FIG. 3.

The developed method for the formation of catalytic layers of solid polymer fuel cells does not require the use of complex technology. When used in membrane-electrode blocks of solid polymer fuel cells, an increased specific power is provided due to an increase in the efficiency of catalysis. When hydrogen is supplied to the anode and air is supplied to the cathode at room temperature, a specific power of 425 mW / cm ^{2 is} achieved, which is significantly higher than for CS prepared using previously existing technologies (180 mW / cm ² ). In addition, the present method has significantly improved the efficiency of platinum use. Mass catalytic activity reached 1150 mW / mg (platinum). Previously existing methods have this indicator equal to 290 mW / mg (platinum). The catalytic layers prepared using FMSCNT, allow to obtain a significantly greater (2.4 times) specific power compared with layers without FMSCNT (Figs. 1 and 2). The mass catalytic activity of platinum (platinum utilization efficiency) depends on the content of FMSCNTs in the catalytic layer and has a maximum at a content of about 10%. The maximum specific power of the catalytic layers containing FMSCNTs increases with an increase in the loading of platinum, but the MCA of platinum (the efficiency of use of platinum) decreases.

Claims (4)

1. A method of forming a catalytic layer of a solid polymer fuel cell, comprising treating multi-walled carbon nanotubes with gas plasma in an inorganic gas or inorganic gas mixture at an electric discharge frequency of 13-40 MHz of an electric discharge power of 0.01-0.1 W / cm ³ and pressure 0 , 20-1.13 Torr for 300-500 s, subsequent processing of multi-walled carbon nanotubes with concentrated nitric acid at a temperature of 100-120 ° C for 5-10 minutes, cooling the first suspension to room temperature s, filtering out multi-walled carbon nanotubes from it, washing them with distilled water and drying at room temperature, mixing dried multi-walled carbon nanotubes with platinum carbon black containing 20-40 wt.% platinum, isopropanol and an aqueous Nafion solution, calculated on the dry matter in the ratio, wt.%:
multi-walled carbon nanotubes 0.15-1.8 platinum carbon black 1,5-4,5 nafion 0.44-1.20 isopropanol 94-98
sonication of the obtained second suspension for 30-60 minutes and subsequent spraying of the second suspension onto a proton-conducting membrane based on a perfluorinated sulfopolymer heated to a temperature of 70-90 ° C. 2. The method according to claim 1, characterized in that Nafion is used as the perforated sulfopolymer. 3. The method according to claim 1, characterized in that the second suspension is sprayed with an airbrush through a metal mask with an opening equal to the specified size of the catalytic layer. 4. The method according to claim 1, characterized in that the inorganic gas is a gas selected from the group: nitrogen, argon, carbon dioxide, oxygen and mixtures thereof.

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