Cathode catalyst layer for proton exchange membrane fuel cell and preparation method and application thereof

Abstract

The application discloses a cathode catalytic layer of a proton exchange membrane fuel cell and a preparation method and application thereof, and the cathode catalytic layer comprises a substrate, and a carbon film with an ordered array carbon nanotube-Turing structure graphene composite structure is grown on the surface of the substrate; Pt particles are loaded in the carbon film, and the content of Pt is <0.1 mg cm ‑2 The cathode catalytic layer of the application is an ordered array carbon nanotube-Turing structure graphene composite structure cathode catalytic layer, has efficient charge and mass transfer channels, and particularly has outstanding oxygen transmission efficiency. The composite electrode structure can better adapt to the uneven concentration distribution of protons, electrons and oxygen in the cathode catalytic layer of the fuel cell, and can greatly improve the proton transmission capacity and the utilization rate of Pt. Meanwhile, the structure is used as the cathode catalytic layer to test the electrochemical behavior of a full cell, and the result shows that the fuel cell single cell performance constructed by the composite electrode has more outstanding performance and higher efficient charge and mass transfer capacity than a commercial Pt / C electrode.

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 applications thereof. Background Art

[0002] The membrane electrode assembly (MEA) is the core component of proton exchange membrane fuel cells (PEMFCs). It consists of a cathode and an anode, located on either side 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 are the primary factor limiting fuel cell applications. Traditional cathode electrodes, formed by a disordered stack of commercial Pt / C catalysts, exhibit blocked pores and tortuous, discontinuous charge and mass transfer channels, significantly hindering fuel cell performance.

[0003] Traditional MEA electrodes are constructed by mixing Pt / C catalyst powder, ion resin solution and isopropyl alcohol into a slurry and spraying it onto 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. At ultra-low Pt (<0.1mg Pt cm -2 ) usage, the randomly distributed ionomer network and discontinuous electron channels of traditional electrodes further increase the local oxygen transport resistance at the three-phase interface. In addition, the uneven concentration distribution of protons, electrons, and oxygen during fuel cell operation leads to low Pt utilization in traditional electrodes. Therefore, the construction method of traditional MEA electrodes is difficult to meet the activity and stability requirements of fuel cells at ultra-low Pt usage.

[0004] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not be regarded as an admission 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, a preparation method and application thereof, so as to overcome the shortcomings of incomplete electrode proton transmission channels, low Pt utilization, and high oxygen transmission resistance at ultra-low Pt usage.

[0006] To achieve the above objectives, the present invention provides a cathode catalyst layer for a proton exchange membrane fuel cell, comprising a substrate, a carbon film having an ordered array of carbon nanotubes and a Turing-structured graphene composite structure grown on the surface of the substrate, and Pt particles loaded in the carbon film, with a Pt content of <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, the thickness of the cathode catalyst layer of the proton exchange membrane fuel cell and 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) Aluminum foil is used as a substrate and pretreated to serve 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-structured graphene composite structure on the surface of an aluminum foil substrate by a chemical vapor deposition method;

[0012] (3) Atomic layer deposition is used to deposit Pt nanoparticles in 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 in step (2) is below 5 Pa, the temperature is raised to 500-650°C under 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.

[0015] Preferably, in the above technical solution, in step (3) the Pt nanoparticles are deposited using trimethylmethylcyclopentadienylplatinum 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 proton exchange membrane fuel cell;

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

[0020] (3) Place the gas diffusion layer on the cathode side, and place the gas diffusion layer sprayed with Pt / C catalyst on the other side of the proton exchange membrane as the anode, and construct a fuel cell membrane electrode by hot pressing.

[0021] Preferably, in the above technical solution, the ionic resin solution is Nafion solution, the ionic 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) includes 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 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, which can greatly improve the proton transfer capacity and the utilization rate of Pt. At the same time, the structure was used as the cathode catalyst layer to test the electrochemical behavior of the entire cell. The results showed that the performance of the fuel cell single cell constructed with 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 the 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 the ALD and electrostatic spraying method to deposit Pt nanocatalyst particles in the composite carbon carrier structure and construct an orderly proton transmission channel. Finally, the composite structure electrode is transferred to one side of the proton exchange membrane as the fuel cell cathode electrode. The electrode constructed by this method has an orderly 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 The invention discloses an ordered array carbon nanotube-Turing structure graphene composite structure electrode;

[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 aluminum foil as a substrate;

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

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

[0034] Figure 2These are scanning electron micrographs of the composite carbon structure film at different plasma powers and different growth times at 220W according to the present invention.

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

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

[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 with 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 graphs 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 sample. DETAILED DESCRIPTION

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

[0046] Unless expressly 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 other components.

[0047] Example 1

[0048] The preparation of a cathode catalyst layer and an electrode of a 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 material, and evaporating 2nm thick Fe at a current of 35mA as a catalyst for the composite carbon structure, that is, the growth substrate of the composite structure;

[0050] (2) Place the Fe-loaded aluminum foil in a plasma-enhanced chemical vapor deposition apparatus, 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 the plasma power to 220 W. After growing for 2 h, turn off the plasma and acetylene. Cool to room temperature in a hydrogen atmosphere and remove the sample.

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

[0052] (4) Using an electrostatic spraying method, the ion resin solution diluted with isopropyl alcohol 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 hot press temperature was adjusted to 135°C and the pressure to 480 kgf / cm 2 , preheating for 10 minutes, and hot pressing for 720 seconds, the composite structure can be transferred to one side of the proton exchange membrane as a cathode.

[0054] (6) Place a gas diffusion layer (the gas diffusion layer is a carbon cloth or carbon paper containing a microporous layer, in this embodiment, carbon paper) on the cathode side, and place a gas diffusion layer sprayed with Pt / C on the other side of the proton exchange membrane as the anode. Adjust the hot press temperature to 135°C and the pressure to 12 kgf / cm 2 , preheating for 10 minutes, and hot pressing for 12 seconds to obtain the MEA. The MEA was 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 a cathode catalyst layer and an electrode of a 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 material, and evaporating 2nm thick Fe at a current of 35mA as the catalyst for the composite carbon structure, that is, the growth substrate of the composite structure;

[0059] (2) Place the Fe-loaded aluminum foil in a plasma-enhanced chemical vapor deposition (PECVD) apparatus, 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 the plasma power to 150 W, 220 W, and 260 W, respectively, for a growth time of 2 h. Also, adjust the growth time at 220 W to 1 h, 2 h, 4 h, and 6 h. Then, turn off the plasma and acetylene, cool to room temperature in a hydrogen atmosphere, and remove the sample.

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

[0061] (4) Using an electrostatic spraying method, the ion resin solution diluted with isopropyl alcohol 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 hot press temperature was adjusted to 135°C and the pressure to 480 kgf / cm 2 , preheating for 10 minutes, and hot pressing for 720 seconds, the composite structure can be transferred to one side of the proton exchange membrane as a cathode.

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

[0064] Figure 2 Scanning electron micrographs showing the composite carbon structures prepared at different growth times at different plasma powers and at 220 W power.

[0065] Example 3

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

[0067] 1. The composite structure electrode as the cathode (wherein the Pt loading was 80 ± 2.5 μg cm -2 -2) and the commercial Pt / C as the anode (wherein the Pt loading was 200 μg cm -2 -2).

[0068] 2. The composite structure electrode as the cathode (wherein the Pt loading was 80 ± 2.5 μg cm -2 -2) at different growth times and the commercial Pt / C as the anode (wherein the Pt loading was 200 μg cm -2 -2).

[0069] 3. The commercial Pt / C as the cathode (wherein the Pt loading was 200 μg cm -2 -2) and the commercial Pt / C as the anode (wherein the Pt loading was 200 μg cm -2 -2).

[0070] Polarization curves and power density curves were obtained at 80°C, a back pressure of 150kPa, and a hydrogen / air flow ratio of 500 / 1000sccm. The electrochemical active area was calculated using cyclic voltammetry at 25°C, a hydrogen / nitrogen flow ratio of 200 / 100sccm, and a scan rate of 200mV / min. Oxygen transport resistance was calculated using limiting current measurements under the following conditions: 80°C, a hydrogen / mixed gas (oxygen and nitrogen with an oxygen concentration of 2%) flow ratio of 800 / 1200sccm, and polarization curves at multiple back pressures (100.0kPa, 120.0kPa, 140.0kPa, 160.0kPa, 180.0kPa, and 200.0kPa) at a scan rate of 5mV / s. The proton transport capacity of the electrodes was compared by electrochemical impedance spectroscopy (EIS) with a test frequency of 2600 Hz to 0.1 Hz, a test potential of 0.5 V, and a perturbation of 5%. The charge transport capacity of the electrodes was described by EIS with a test frequency of 10 kHz to 0.1 Hz and a test current density of 0.8 A cm -2 and performed at a perturbation of 10%.

[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 each electrode as above 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 efficient oxygen transport capability, and its oxygen transport efficiency is 2.5 times that of the commercial Pt / C electrode.

[0072] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A cathode catalyst layer of a proton exchange membrane fuel cell, characterized in that: The cathode catalyst layer comprises a carbon film of an ordered array of carbon nanotubes and a Turing structure graphene composite structure, wherein Pt particles are loaded in the carbon film, and the Pt content is less than 0.1 mg cm -2 ; A method for preparing a cathode catalyst layer of a proton exchange membrane fuel cell comprises the following steps: (1) Using aluminum foil as a substrate, pre-treating it and using it as a substrate for composite structure growth; (2) A carbon source and hydrogen are mixed, and a carbon film having an ordered array of carbon nanotubes and a Turing-structured graphene composite structure is grown on the surface of an aluminum foil substrate by chemical vapor deposition; (3) Platinum nanoparticles are deposited in an ordered array of carbon nanotubes-Turing structure graphene composite structure by atomic layer deposition, and then an ion resin solution is sprayed on the surface of the composite structure to obtain a cathode catalyst layer by transfer printing; 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; In 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 plasma power is 150-260 W, and the reaction time is 1-4 h.

2. 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.

3. The cathode catalyst layer of the proton exchange membrane fuel cell according to claim 2, characterized in that: The thickness of the ordered array carbon nanotube-Turing structure graphene is 3 μm.

4. The cathode catalyst layer of the proton exchange membrane fuel cell according to claim 1, characterized in that: Step (3) Pt nanoparticle deposition uses trimethylmethylcyclopentadiene platinum as the Pt source, oxygen as the oxygen source, and the Pt source temperature is 65-85°C.

5. Use of the cathode catalyst layer of a proton exchange membrane fuel cell according to any one of claims 1 to 4, for the cathode of a proton exchange membrane fuel cell or for preparing an electrode of a proton exchange membrane fuel cell.

6. A method for preparing an electrode for a proton exchange membrane fuel cell, characterized in that: The following steps are involved: (1) The cathode catalyst layer of the proton exchange membrane fuel cell according to claim 1 is transferred to one side of the proton exchange membrane as a composite structure cathode electrode; (2) Place the gas diffusion layer on the cathode side, and place the gas diffusion layer sprayed with Pt / C catalyst on the other side of the proton exchange membrane as the anode, and construct a fuel cell membrane electrode by hot pressing.

7. The method for preparing an electrode for a proton exchange membrane fuel cell according to claim 6, 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; The transfer in step (1) 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; The hot pressing in step (2) 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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