Cathode catalyst layer of proton exchange membrane fuel cell as well as preparation method and application of cathode catalyst layer

Abstract

The invention discloses a cathode catalyst layer of a proton exchange membrane fuel cell as well as a preparation method and application of the cathode catalyst layer, the cathode catalyst layer comprises a substrate, a carbon film with an ordered array carbon nanotube-Turing structure graphene composite structure grows on the surface of the substrate, Pt particles are loaded in the carbon film, and the content of Pt is 1t; and 0.1 mg cm <-2 >. The cathode catalyst layer disclosed by the invention is a cathode catalyst layer with an ordered array carbon nanotube-Turing structure graphene composite structure, has an efficient load and mass transfer channel, and particularly has outstanding oxygen transmission efficiency. The composite electrode structure can better adapt to non-uniform concentration distribution of protons, electrons and oxygen in a fuel cell cathode catalyst layer, and can greatly improve the proton transmission capability and the Pt utilization rate. Meanwhile, the structure is used as a cathode catalyst layer for testing the electrochemical behavior of the whole cell, and the result shows that the single cell performance of the fuel cell constructed by the composite electrode is more prominent than that of a commercial Pt / C electrode and has more efficient load and mass transfer capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of proton exchange membrane fuel cells, and in particular to a cathode catalyst layer of a proton exchange membrane fuel cell, a preparation method thereof and an application thereof. Background Art

[0002] The fuel cell membrane electrode assembly (MEA) is the core component of the proton exchange membrane fuel cell. It consists of a cathode and an anode distributed on both sides of the proton exchange membrane. The oxygen reduction reaction at the cathode and the hydrogen oxidation reaction at the anode are the core reactions. The slow kinetics of the oxygen reduction reaction has become the most important factor restricting the application of fuel cells. The traditional cathode electrode is formed by the disordered stacking of commercial Pt / C catalysts. Its internal blocked pore structure and the tortuous and discontinuous charge and mass transfer channels greatly hinder the performance of the fuel cell.

[0003] Traditional MEA electrodes are made by mixing Pt / C catalyst powder, ion resin solution and isopropanol into slurry and spraying it on the gas diffusion layer. This electrode preparation method has the following disadvantages: 1. The slurry made by mixing multiple components is unevenly dispersed, resulting in incomplete proton transmission channels and low Pt catalyst utilization. 2. The electrodes constructed by spraying are disordered, and the gas transmission channels are tortuous, causing a sharp increase in oxygen transmission resistance. 3. In the case of ultra-low Pt (<0.1mg Pt cm -2 ) usage, the randomly distributed ionomer network and discontinuous electron channels of the traditional electrode further increase the local oxygen transport resistance at the three-phase interface. In addition, the uneven concentration distribution of protons, electrons and oxygen during the operation of the fuel cell leads to the problem of low Pt utilization of the traditional electrode. Therefore, the construction method of the traditional MEA electrode is difficult to meet the activity and stability requirements of the fuel cell at ultra-low Pt usage.

[0004] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0005] The purpose of the present invention is to provide a cathode catalyst layer of a proton exchange membrane fuel cell and a preparation method and application thereof, so as to overcome the shortcomings of incomplete electrode proton transmission channel, low Pt utilization, and large oxygen transmission resistance at ultra-low Pt usage.

[0006] To achieve the above object, the present invention provides a cathode catalyst layer of a proton exchange membrane fuel cell, comprising a substrate, a carbon film having an ordered array of carbon nanotubes-Turing structure graphene composite structure grown on the surface of the substrate, and Pt particles loaded in the carbon film, wherein the content of Pt is <0.1 mg cm -2 .

[0007] Preferably, in the above technical solution, the substrate of the cathode catalyst layer of the proton exchange membrane fuel cell is aluminum foil.

[0008] Preferably, in the above technical solution, in the cathode catalyst layer of the proton exchange membrane fuel cell, the thickness of the ordered array carbon nanotube-Turing structure graphene is 1-5 μm, preferably 3 μm.

[0009] A method for preparing a cathode catalyst layer of a proton exchange membrane fuel cell comprises the following steps:

[0010] (1) Using aluminum foil as a substrate, pre-treating it, and using it as a substrate for growing a composite structure;

[0011] (2) mixing a carbon source and hydrogen, and growing a carbon film having an ordered array of carbon nanotubes and a Turing structure graphene composite structure on a surface of an aluminum foil substrate by a chemical vapor deposition method;

[0012] (3) Atomic layer deposition is used to deposit Pt nanoparticles into an ordered array of carbon nanotubes-Turing structure graphene composite structure as a cathode catalyst layer.

[0013] Preferably, in the above technical solution, the pretreatment of the aluminum foil in step (1) includes cleaning the surface of the aluminum foil and evaporating Fe particles with a thickness of 1-5 nm on the surface of the aluminum foil as a growth substrate for the composite structure.

[0014] Preferably, in the above technical solution, the vacuum degree in the reaction equipment of step (2) is below 5 Pa, the temperature is raised to 500-650°C in a hydrogen atmosphere, the carbon source is acetylene, the flow ratio of hydrogen to acetylene is 10-20:30-80sccm; the power of the reaction equipment is 150-260W, and the reaction time is 1-4h.

[0015] Preferably, in the above technical solution, in step (3) the Pt nanoparticles are deposited using trimethyl methylcyclopentadienyl platinum as the Pt source, oxygen as the oxygen source, and the Pt source temperature is 65-85°C.

[0016] A use of a cathode catalyst layer of a proton exchange membrane fuel cell, which is used for the cathode of a proton exchange membrane fuel cell or for preparing an electrode of a proton exchange membrane fuel cell.

[0017] A method for preparing an electrode for a proton exchange membrane fuel cell comprises the following steps:

[0018] (1) spraying an ion resin solution on the surface of the cathode catalyst layer of the above-mentioned proton exchange membrane fuel cell;

[0019] (2) transferring the composite material of step (1) onto one side of the proton exchange membrane as a composite structure cathode electrode;

[0020] (3) The gas diffusion layer is placed on the cathode side, and the gas diffusion layer sprayed with Pt / c catalyst is placed on the other side of the proton exchange membrane as the anode, and then constructed into a fuel cell membrane electrode by hot pressing.

[0021] Preferably, in the above technical solution, the ion resin solution is a Nafion solution, the ion resin solution is diluted to 1-3 mg / ml, and the spraying loading is 5-25 μg / cm 2 ; The proton exchange membrane is an NRE 211 (DuPont) electrolyte membrane, and the gas diffusion layer is a carbon cloth or carbon paper containing a microporous layer;

[0022] Preferably, in the above technical solution, the transfer method in step (2) includes a temperature of 120-150°C and a pressure of 400-500 kgf cm -2 , preheating time is 5-20min, transfer time is 300-1000s.

[0023] Preferably, in the above technical solution, the hot pressing method in step (3) comprises a temperature of 120-150°C and a pressure of 5-20 kgfcm -2 , preheating time 5-20min, hot pressing time 5-20s.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The cathode catalyst layer of the proton exchange membrane fuel cell of the present invention has an ordered array carbon nanotube-Turing structure graphene composite structure, which has a highly efficient charge and mass transfer channel compared to the conventional disordered stacked electrodes, and has particularly outstanding oxygen transfer efficiency. In addition, the composite electrode structure can better adapt to the uneven concentration distribution of protons, electrons and oxygen in the cathode catalyst layer of the fuel cell, and can greatly improve the proton transfer capacity and the utilization rate of Pt. At the same time, the structure is used as the cathode catalyst layer to test the electrochemical behavior of the whole cell. The results show that the performance of the fuel cell single cell constructed by the composite electrode has more outstanding performance and more efficient charge and mass transfer capabilities than the commercial Pt / C electrode.

[0026] (2) The cathode catalyst layer of the proton exchange membrane fuel cell of the present invention is used to prepare a membrane electrode. The carbon nanotubes arranged in an orderly array in the cathode catalyst layer provide orderly and high-speed oxygen transmission, proton transmission and electron transmission channels. The top Turing structure graphene strengthens the contact between the electrode and the PEM and reduces the interface contact resistance. At the same time, the nanosheets can carry more Pt to improve the utilization rate of the electrode. The ALD method deposits Pt catalyst nanoparticles on the surface of the carbon composite structure with a more efficient Pt utilization rate, which can greatly reduce the amount of Pt used. Therefore, the ordered array carbon nanotube-Turing structure graphene composite electrode construction strategy has exerted excellent performance in ultra-low platinum fuel cells.

[0027] (3) The preparation method of the present invention mainly uses a plasma chemical vapor deposition method to grow a composite structure carbon film on the surface of aluminum foil as the main frame of the fuel cell cathode, and then uses ALD and electrostatic spraying methods to deposit Pt nanocatalyst particles in the composite carbon carrier structure and construct an ordered proton transmission channel, and finally transfers the composite structure electrode to one side of the proton exchange membrane as a fuel cell cathode electrode. The electrode constructed by this method has an ordered structure that can promote oxygen transmission in the electrode. At the same time, the top Turing structure graphene carries more Pt nanoparticles and ionomers to meet the uneven proton concentration in the actual reaction process, thereby enhancing the proton transmission efficiency and improving the utilization rate of Pt. Through the performance of the fuel cell test, it was found that the ultra-low platinum fuel cell system constructed by this method showed excellent performance far exceeding commercial Pt / C in the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the ordered array carbon nanotube-Turing structure graphene composite structure electrode of the present invention;

[0029] in, Figure 1 (a) is a scanning electron microscope image of an ordered array of carbon nanotubes-Turing structure graphene composite carbon structure grown on an aluminum foil substrate;

[0030] (b) is a top view of a scanning electron microscope image of an ordered array carbon nanotube-Turing structure graphene composite carbon structure;

[0031] (c) is a cross-sectional view of an ordered array carbon nanotube-Turing structure graphene composite carbon structure;

[0032] (d) is a schematic diagram of the application of ordered array carbon nanotube-Turing structure graphene composite structure electrode in fuel cells;

[0033] (e) is a focused ion beam scanning electron microscope image of an ordered array carbon nanotube-Turing structure graphene composite structure electrode;

[0034] Figure 2It is a scanning electron micrograph of the composite carbon structure film under different plasma powers and different growth times at 220W according to the present invention.

[0035] Figure (a) is a top view of a scanning electron micrograph of a composite carbon structure film grown for 2h at 150W power;

[0036] Figure (b) is a top view of a scanning electron micrograph of a composite carbon structure film grown for 2h at 220W power;

[0037] Figure (c) is a top view of a scanning electron micrograph of a composite carbon structure film grown at 260W power for 2h.

[0038] Figure 3 This is an electrochemical test diagram of a fuel cell prepared by the ordered array carbon nanotube-Turing structure graphene composite structure electrode of the present invention;

[0039] (a) Polarization curves and power density curves of the composite electrodes with different growth times as cathodes and commercial Pt / C as cathodes;

[0040] (b) CV test graph of each electrode;

[0041] (c) Oxygen transmission resistance of each sample;

[0042] (d) Linear relationship between oxygen transmission resistance and pressure;

[0043] (e) proton transport resistance;

[0044] (f) Electrochemical impedance spectroscopy of the samples. DETAILED DESCRIPTION

[0045] The specific implementation modes of the present invention are described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific implementation modes.

[0046] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0047] Example 1

[0048] The preparation of the cathode catalyst layer and the electrode of the proton exchange membrane fuel cell comprises the following steps:

[0049] (1) Cut the aluminum foil into 5.5 cm × 5.5 cm size, clean the surface with anhydrous ethanol, stick the cut aluminum foil into the e-beam chamber, and evacuate the chamber to a vacuum degree of 5 × 10 -6torr, voltage 10kV, using Fe particles as raw materials, evaporating 2nm thick Fe at a current of 35mA as a catalyst for the composite carbon structure, i.e., the growth substrate of the composite structure;

[0050] (2) The Fe-loaded aluminum foil was placed in a plasma enhanced chemical vapor deposition device, evacuated to below 5 Pa and heated to 600 ° C in a hydrogen atmosphere, the hydrogen / acetylene flow ratio was adjusted to 20 / 60 sccm, the plasma power was 220 W, and the plasma and acetylene were turned off after 2 h of growth. The sample was cooled to room temperature in a hydrogen atmosphere and taken out;

[0051] (3) The sample was placed in an ALD device for deposition of Pt catalyst nanoparticles; the Pt source was trimethylmethylcyclopentadienyl platinum, oxygen was used as the oxygen source, and one deposition cycle was as follows: 1. The chamber reaction temperature was 300°C, the Pt source pulse time was 300 ms, and the reaction time was 5 s after entering the chamber; 2. Nitrogen purge was 15 s; 3. Oxygen reaction was 1 s; 4. Nitrogen purge was 15 s, and the total number of reaction cycles was 85 times, and the Pt loading was about 80±2.5 μgcm -2 .

[0052] (4) Using an electrostatic spraying method, the ion resin solution diluted with isopropanol is evenly sprayed on the surface of the composite structure electrode in step (3) to construct an ion transmission channel. The ion resin solution is DuPont Nafion solution D520; the ion resin solution is diluted to 2 mg / ml, and the spraying load is 10 ug / cm 2 .

[0053] (5) The sample was placed on one side of the proton exchange membrane, which was an NRE 211 (DuPont) electrolyte membrane. The temperature of the hot press was adjusted to 135°C and the pressure to 480 kgf / cm 2 , preheat for 10 minutes, and hot press for 720 seconds, and then the composite structure can be transferred to one side of the proton exchange membrane as a cathode.

[0054] (6) A gas diffusion layer (the gas diffusion layer is a carbon cloth or carbon paper containing a microporous layer, and in this embodiment, carbon paper) is placed on the cathode side, and a gas diffusion layer sprayed with Pt / C is placed on the other side of the proton exchange membrane as an anode. The hot press temperature is adjusted to 135°C and the pressure is 12 kgf / cm 2 , preheating for 10 minutes, hot pressing for 12 seconds, and then MEA can be obtained. The MEA is placed in a PEMFC single cell fixture to form a single cell for testing.

[0055] Figure 1 Shown are scanning electron microscope images of the composite carbon structure and the composite structure electrode.

[0056] Example 2

[0057] The preparation of the cathode catalyst layer and the electrode of the proton exchange membrane fuel cell comprises the following steps:

[0058] (1) Cut the aluminum foil into 5.5 cm × 5.5 cm size, clean the surface with anhydrous ethanol, stick the cut aluminum foil into the e-beam chamber, and evacuate the chamber to a vacuum degree of 5 × 10 -6 torr, voltage 10kV, using Fe particles as raw materials, and evaporating 2nm thick Fe at a current of 35mA as a catalyst for the composite carbon structure, i.e., the growth substrate of the composite structure;

[0059] (2) Place the Fe-loaded aluminum foil in a plasma enhanced chemical vapor deposition device, evacuate to below 5 Pa and heat to 600°C in a hydrogen atmosphere, adjust the hydrogen / acetylene flow ratio to 20 / 60 sccm, and adjust the plasma power to 150w, 220w, and 260w, respectively, for a growth time of 2h; and adjust the growth time to 1h, 2h, 4h, and 6h at a power of 220w. Then turn off the plasma and acetylene, cool to room temperature in a hydrogen atmosphere, and take out the sample;

[0060] (3) The sample was placed in an ALD device for deposition of Pt catalyst nanoparticles; the Pt source was trimethylmethylcyclopentadienyl platinum, oxygen was used as the oxygen source, and one deposition cycle was as follows: 1. The chamber reaction temperature was 300°C, the Pt source pulse time was 300 ms, and the reaction time was 5 s after entering the chamber; 2. Nitrogen purge was 15 s; 3. Oxygen reaction was 1 s; 4. Nitrogen purge was 15 s, and the total number of reaction cycles was 85 times, and the Pt loading was about 80±2.5 μgcm -2 .

[0061] (4) Using an electrostatic spraying method, the ion resin solution diluted with isopropanol is evenly sprayed on the surface of the composite structure electrode in step (3) to construct an ion transmission channel. The ion resin solution is DuPont Nafion solution D520; the ion resin solution is diluted to 2 mg / ml, and the spraying load is 10 ug / cm 2 .

[0062] (5) The sample was placed on one side of the proton exchange membrane, which was an NRE 211 (DuPont) electrolyte membrane. The temperature of the hot press was adjusted to 135°C and the pressure to 480 kgf / cm 2 , preheat for 10 minutes, and hot press for 720 seconds, and then the composite structure can be transferred to one side of the proton exchange membrane as a cathode.

[0063] (6) A gas diffusion layer (the gas diffusion layer is a carbon cloth or carbon paper containing a microporous layer, and in this embodiment, carbon paper) is placed on the cathode side, and a gas diffusion layer sprayed with Pt / C is placed on the other side of the proton exchange membrane as an anode. The hot press temperature is adjusted to 135°C and the pressure is 12 kgf / cm 2 , preheat for 10 minutes, and hot press for 12 seconds to obtain MEA; the MEA is placed in a PEMFC single cell fixture to form a single cell for testing.

[0064] Figure 2 Shown are scanning electron micrographs of composite carbon structures prepared at different plasma powers and different growth times at 220W power.

[0065] Example 3

[0066] like Figure 3 As shown, the electrochemical behavior of the fuel cell cells constructed with the following electrodes were tested:

[0067] 1. Composite structure electrode as cathode (where Pt loading is 80±2.5μgcm -2 ), commercial Pt / C as anode (with a Pt loading of 200 μg cm -2 ).

[0068] 2. Composite structure electrodes with different growth times as cathodes (where Pt loading is 80±2.5μgcm -2 ), commercial Pt / C as anode (with a Pt loading of 200 μg cm -2 ).

[0069] 3. Commercial Pt / C as cathode (with Pt loading of 200 μg cm -2 ), commercial Pt / C as anode (with a Pt loading of 200 μg cm -2 ).

[0070] Polarization curve and power density curve are obtained under the conditions of temperature 80℃, back pressure 150kPa, and hydrogen / air flow ratio of 500 / 1000sccm. The calculation of electrochemical active area is obtained by cyclic voltammetry test, where the test conditions are temperature 25℃, hydrogen / nitrogen flow ratio 200 / 100sccm, and scan rate 200mV / min. Oxygen transmission resistance is obtained by limiting current test and calculation, and the specific test conditions are: temperature 80℃, hydrogen / mixed gas (mixed gas components oxygen and nitrogen with oxygen concentration 2%) flow ratio of 800 / 1200sccm, and polarization curve test of multiple back pressures (100.0kPa, 120.0kPa, 140.0kPa, 160.0kPa, 180.0kPa, 200.0kPa) at a scan rate of 5mV / s, and limiting current density. The proton transport capacity in the electrode was compared by electrochemical impedance spectroscopy, where the electrochemical impedance frequency was 2600Hz-0.1Hz, the test potential was 0.5V, and the perturbation was 5%. The charge transport capacity in the electrode was described by electrochemical impedance spectroscopy, where the test frequency was 10kHz-0.1Hz and the test current density was 0.8Acm -2 and performed at 10% perturbation.

[0071] like Figure 3 As shown, in the embodiment of the present invention, a method for preparing an ordered array carbon nanotube-Turing structure graphene composite structure electrode for ultra-low platinum loading proton exchange membrane fuel cell is prepared. The ordered carbon nanotubes in the composite structure electrode can provide efficient oxygen transmission capacity for the electrode, and the composite Turing structure graphene can not only enhance the contact area between the electrode and PEM, reduce the electron transmission resistance, but also provide an efficient proton transmission channel. The fuel cell polarization curve test of the above electrodes shows that when the Pt loading is 80μgcm -2 The power density of the composite electrode is 1128 mW / cm 2 , which is 1.47 times the power density of commercial Pt / C (Pt loading is 200 μg cm -2 ). In addition, the composite electrode has a highly efficient oxygen transport capability, and its oxygen transport efficiency is 2.5 times that of the commercial Pt / C electrode.

[0072] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A cathode catalyst layer of a proton exchange membrane fuel cell, characterized in that: The invention comprises a substrate, on the surface of which a carbon film of an ordered array carbon nanotube-Turing structure graphene composite structure is grown, and the carbon film is loaded with Pt particles, and the content of Pt is less than 0.1 mg cm -2 .

2. The cathode catalyst layer of the proton exchange membrane fuel cell according to claim 1, characterized in that: The substrate is aluminum foil.

3. The cathode catalyst layer of the proton exchange membrane fuel cell according to claim 1, characterized in that: The thickness of the ordered array carbon nanotube-Turing structure graphene is 1-5 μm, preferably 3 μm.

4. A method for preparing a cathode catalyst layer of a proton exchange membrane fuel cell according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Using aluminum foil as a substrate, pre-treating it, and using it as a substrate for growing a composite structure; (2) mixing a carbon source and hydrogen, and growing a carbon film having an ordered array of carbon nanotubes and a Turing structure graphene composite structure on a surface of an aluminum foil substrate by a chemical vapor deposition method; (3) Atomic layer deposition is used to deposit Pt nanoparticles into an ordered array of carbon nanotubes-Turing structure graphene composite structure as a cathode catalyst layer.

5. The preparation method according to claim 4, characterized in that: Step (1) pretreatment of the aluminum foil includes cleaning the surface of the aluminum foil and evaporating Fe particles with a thickness of 1-5 nm on the surface of the aluminum foil as a growth substrate for the composite structure.

6. The preparation method according to claim 4, characterized in that: Step (2) The vacuum degree in the reaction equipment is below 5 Pa, and the temperature is raised to 500-650° C. in a hydrogen atmosphere. The carbon source is acetylene, and the flow ratio of hydrogen to acetylene is 10-20:30-80 sccm. The power of the reaction equipment is 150-260 W, and the reaction time is 1-4 h.

7. The preparation method according to claim 4, characterized in that: Step (3) Pt nanoparticle deposition uses trimethylmethylcyclopentadienyl platinum as the Pt source, oxygen as the oxygen source, and the Pt source temperature is 65-85°C.

8. Use of the cathode catalyst layer of a proton exchange membrane fuel cell as claimed in any one of claims 1 to 7 for the cathode of a proton exchange membrane fuel cell or for preparing an electrode of a proton exchange membrane fuel cell.

9. A method for preparing an electrode for a proton exchange membrane fuel cell, characterized in that: The following steps are involved: (1) spraying an ion resin solution on the surface of the cathode catalyst layer of the proton exchange membrane fuel cell according to claim 1; (2) transferring the composite material of step (1) onto one side of the proton exchange membrane as a composite structure cathode electrode; (3) The gas diffusion layer is placed on the cathode side, and the gas diffusion layer sprayed with Pt / c catalyst is placed on the other side of the proton exchange membrane as the anode, and then constructed into a fuel cell membrane electrode by hot pressing.

10. The method for preparing an electrode for a proton exchange membrane fuel cell according to claim 9, characterized in that: The ion resin solution is Nafion solution, which is diluted to 1-3 mg / ml, and the spraying loading is 5-25 μg / cm 2 ; The proton exchange membrane is an NRE 211 electrolyte membrane, and the gas diffusion layer is a carbon cloth or carbon paper containing a microporous layer; Step (2) The transfer method includes a temperature of 120-150°C and a pressure of 400-500 kgf cm -2 , preheating time is 5-20min, transfer time is 300-1000s; Step (3) hot pressing includes a temperature of 120-150°C and a pressure of 5-20 kgf cm -2 , preheating time 5-20min, hot pressing time 5-20s.

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