Hydrophilic and hydrophobic regulation-based hydrogen fuel cell catalyst layer slurry and membrane electrode preparation method

Abstract

The invention belongs to the technical field of membrane electrodes, and particularly relates to a hydrogen fuel cell catalyst layer slurry based on hydrophilic and hydrophobic regulation and a preparation method of a membrane electrode. The slurry of the catalyst layer comprises the following contents: the slurry of the PEM close to the cathode side comprises a Pt / C catalyst, deionized water, a perfluorosulfonic acid ionic polymer solution and isopropanol; the mass ratio, namely I / C ratio, of the ionic polymer to the carbon carrier is 0.8-1.2; the GDL cathode side slurry comprises a Pt / C catalyst, deionized water, a perfluorosulfonic acid ionic polymer solution, a PTFE aqueous solution (polytetrafluoroethylene aqueous solution) and isopropanol, and the mass ratio of the ionic polymer to the carbon carrier, namely I / C ratio, is 0.3-0.5. High hydrophilic ionomer content is reserved on the side, close to the cathode, of the PEM, proton conduction and catalyst active site wetting are guaranteed, the proportion of hydrophobic ionomers and hydrophobic materials is increased on the GDL side, a drainage channel is formed, liquid water is prevented from blocking gaps, then the performance of the membrane electrode is remarkably improved, and the interface contact resistance is stabilized to be 1.64-1.76 m omega (2.5 A / cm < 2 >).

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane electrodes. More specifically, it relates to a method for preparing a hydrogen fuel cell catalyst layer slurry and a membrane electrode based on hydrophilic-hydrophobic regulation. Background Art

[0002] Currently, the preparation technology of hydrogen fuel cell catalyst layers mostly adopts a single-layer spraying process, which focuses on controlling the catalyst loading while ignoring the regulation of water transport by the hydrophilic-hydrophobic characteristics of the ionomer. This technical defect seriously restricts the durability and output performance of fuel cells under high current density conditions. The literature (DOI 10.1149 / 1.3546038; DOI 10.1149 / 1.1646148) aims to solve the problem that the oxygen mass transfer impedance sharply increases due to flooding on the cathode catalyst layer (CL) side, and the local current density distribution is uneven due to the blockage of the proton conduction network on the anode side by liquid water, thereby increasing the concentration polarization loss. There is an urgent need to develop a method for the directional construction of a catalyst layer based on the synergistic regulation of hydrophilicity and hydrophobicity, and use a double-layer ultrasonic spraying technique to coat hydrophilic ionomer, catalyst, and water alcohol on both sides of a perfluorosulfonic acid proton membrane (PEM), and coat hydrophobic ionomer, catalyst, and water alcohol on the gas diffusion layer (GDL) side to prepare a highly hydrophobic membrane electrode assembly. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defects and deficiencies existing in the prior art, and provide a method for preparing a hydrogen fuel cell catalyst layer slurry and a membrane electrode based on hydrophilic-hydrophobic regulation. The present invention aims to solve the problems of increased mass transfer impedance and uneven local current density distribution caused by flooding of the catalyst layer under high current density (≥2 A / cm 2 ), and at 0.6 V, the current density is 2.8 A / cm 2 , while reducing the interfacial contact resistance to below 1.7 mΩ.

[0004] The purpose of the present invention is to provide a hydrogen fuel cell catalyst layer slurry based on hydrophilic-hydrophobic regulation.

[0005] Another purpose of the present invention is to provide a method for preparing a hydrophilic-hydrophobic double-layer coated membrane electrode.

[0006] The above objects of the present invention are achieved by the following technical solutions:

[0007] A hydrogen fuel cell catalyst layer slurry based on hydrophilic-hydrophobic regulation, comprising the following components:

[0008] The slurry on the cathode side close to the PEM includes Pt / C catalyst, deionized water, perfluorosulfonic acid ionomer solution, and isopropyl alcohol;

[0009] The GDL cathode-side slurry includes Pt / C catalyst, deionized water, perfluorosulfonic acid ionomer solution, PTFE aqueous solution, and isopropanol.

[0010] In the present invention, preferred embodiments include that in the cathode-side slurry near the PEM, the mass ratio of the ionomer to the carbon support, i.e., the I / C ratio, is 0.8 to 1.2; the perfluorosulfonic acid ionomer is a hydrophilic ionomer DFPSA-2179S.

[0011] Furthermore, the Pt loading in the Pt / C is 50 to 70 wt%; the mass ratio of water to isopropanol is 1:1.

[0012] Furthermore, the concentration of the hydrophilic ionomer is 8 to 12 wt%; the solvents are water and n-propanol, and the mass ratio of water to n-propanol is 1:1.

[0013] In the present invention, further preferred embodiments include that in the GDL cathode-side slurry, the mass ratio of the ionomer to the carbon support, i.e., the I / C ratio, is 0.3 to 0.5; the perfluorosulfonic acid ionomer is a hydrophobic ionomer DE 520.

[0014] Furthermore, the Pt loading in the Pt / C is 50 to 70 wt%; the mass ratio of water to isopropanol is 1:1.

[0015] Furthermore, the concentration of the hydrophobic ionomer is 4 to 6 wt%, the solvents are water and n-propanol, and the mass ratio of water to n-propanol is 1:3; the concentration of the PTFE aqueous solution is 5 to 15 wt%.

[0016] Based on the above method for preparing a membrane electrode from a hydrogen fuel cell catalytic layer slurry with hydrophilic-hydrophobic regulation, the preparation method includes the following steps:

[0017] (1) The preparation method of the cathode-side slurry near the PEM includes: mixing Pt / C with deionized water, ultrasonic dispersing for 3 to 7 min, adding the perfluorosulfonic acid ionomer solution, ultrasonic dispersing for 3 to 7 min, and finally adding isopropanol and performing high-speed shearing for 20 to 40 min.

[0018] The preparation method of the GDL cathode-side slurry includes: mixing Pt / C with deionized water, ultrasonic dispersing for 3 to 7 min, adding the perfluorosulfonic acid ionomer solution, ultrasonic dispersing for 3 to 7 min, and finally adding isopropanol and the PTFE aqueous solution and performing high-speed shearing for 20 to 40 min.

[0019] (2) Place the prepared slurry in an ultrasonic spraying machine and perform circular orbit ultrasonic spraying on the PEM according to the program set by the spraying machine.

[0020] Preferably, in the step (1), in the preparation method of the slurry on the cathode side of the PEM, the solid content is 1-10 wt%, and the shear rate is 8000-12000 rpm; in the preparation method of the slurry on the cathode side of the GDL, the solid content is 1-3 wt%, and the shear rate is 8000-12000 rpm.

[0021] Preferably, in the step (2), the spraying area is 25 cm 2 , and 0.1-0.3 mg / cm 2 is sprayed on the cathode side of the PEM; 0.05-0.15 mg / cm 2 is sprayed on the cathode side of the GDL.

[0022] The present invention has the following beneficial effects:

[0023] (1) Hydrophilic ionomers DFPSA-2179S (I / C ratio 0.8) are used on both sides of the PEM, and a hydrophobic ionomer DE 520 and PTFE composite hydrophobic system (I / C ratio 0.4, PTFE content 5-15 wt%) is used on the cathode side of the GDL; a higher content of hydrophilic ionomers is retained on the PEM side to ensure proton conduction and wetting of the catalyst active sites, and the proportion of hydrophobic ionomers and hydrophobic materials (such as PTFE) is increased on the GDL side to form drainage channels and prevent liquid water from blocking the voids;

[0024] (2) Solvent system optimization: Isopropanol / deionized water (mass ratio 1:1) is used as the dispersion medium to enhance hydrophobicity.

[0025] The membrane electrode prepared by the present invention by constructing an ionomer system with a hydrophilic-hydrophobic gradient distribution has a current density of 2.8 A / cm 2 at 0.6 V (test conditions: 80 °C, 100% RH, H2 / Air), which is 40% higher, and the interfacial contact resistance is stable in the range of 1.64-1.76 mΩ (2.5 A / cm 2 ). Description of the Drawings

[0026] Figure 1 is a comparative graph of polarization curves of Examples 1-7.

[0027] Figure 2 Internal resistance meters in different examples during electrochemical testing.

[0028] Figure 3 Schematic diagram of the membrane electrode structure (CCL cathode catalyst layer; ACL anode catalyst layer; PEM perfluorosulfonic acid proton exchange membrane; GDL gas diffusion layer) Detailed Embodiments

[0029] The present invention will be further described below in conjunction with specific embodiments, but the embodiments do not impose any form of limitation on the present invention. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0030] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0031] Example 1

[0032] A method for preparing a membrane electrode specifically includes the following steps:

[0033] (1) Preparation of the slurry on the cathode side of the PEM: 60 wt% Pt / C is mixed with deionized water and ultrasonicated for 5 min, then hydrophilic ionomer DFPSA-2179S (10 wt%; solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:1) is added and ultrasonicated for 5 min. Finally, isopropanol is added and high-speed shearing is carried out for 30 min at a shearing rate of 10000 rpm. Its I / C ratio is 0.8 and the solid content is 2 wt%. The mass ratio of the water to the isopropanol is 1:1;

[0034] Preparation of the slurry on the cathode side of the GDL: 60 wt% Pt / C is mixed with deionized water and ultrasonicated for 5 min, then hydrophobic ionomer DE520 (5 wt%; solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:3) is added and ultrasonicated for 5 min. Finally, 10 wt% PTFE aqueous solution and isopropanol are added and high-speed shearing is carried out for 30 min at a shearing rate of 10000 rpm. Its I / C ratio is 0.4 and the solid content is 2 wt%. The mass ratio of the water to the isopropanol is 1:1.

[0035] (2) Place the prepared slurry in an ultrasonic spraying machine and perform circular orbit ultrasonic spraying on the PEM according to the program set by the spraying machine. The spraying area is 25 cm 2 , where 0.2 mg / cm 2 is sprayed on the cathode side of the PEM, and 0.1 mg / cm 2 is sprayed on the cathode side of the GDL.

[0036] Example 2

[0037] A method for preparing a membrane electrode specifically includes the following steps:

[0038] (1) Preparation of the cathode-side slurry of PEM: Mix 60 wt% Pt / C with deionized water and ultrasonicate for 5 min. Add the amphiphilic ionomer DE 2020 (5 wt%; the solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:3) and ultrasonicate for 5 min. Finally, add isopropanol and perform high-speed shearing for 30 min at a shearing rate of 10,000 rpm. Its I / C ratio is 0.8, and the solid content is 2 wt%. The mass ratio of water to isopropanol is 1:1;

[0039] Preparation of the cathode-side slurry of GDL: Mix 60 wt% Pt / C with deionized water and ultrasonicate for 5 min. Add the hydrophobic ionomer DE520 (5 wt%; the solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:3) and ultrasonicate for 5 min. Finally, add 10 wt% PTFE aqueous solution and isopropanol, and perform high-speed shearing for 30 min at a shearing rate of 10,000 rpm. Its I / C ratio is 0.4, and the solid content is 2 wt%. The mass ratio of water to isopropanol is 1:1.

[0040] (2) Place the prepared slurry in an ultrasonic spraying machine and perform circular orbit ultrasonic spraying on the PEM according to the program set by the spraying machine. The spraying area is 25 cm 2 . Among them, 0.15 mg / cm is sprayed on the cathode side of the PEM 2 , and 0.15 mg / cm is sprayed on the cathode side of the GDL 2 .

[0041] Example 3

[0042] A method for preparing a membrane electrode specifically includes the following steps:

[0043] (1) Preparation of the cathode-side slurry of PEM: Mix 60 wt% Pt / C with deionized water and ultrasonicate for 5 min. Add the hydrophilic ionomer DFPSA-2179S (10 wt%; the solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:1) and ultrasonicate for 5 min. Finally, add isopropanol and perform ultrasonic dispersion for 30 min at a shearing rate of 10,000 rpm. Its I / C ratio is 1.2, and the solid content is 2 wt%. The mass ratio of water to isopropanol is 1:1;

[0044] Preparation of the cathode-side slurry of GDL: Mix 60 wt% Pt / C with deionized water and ultrasonicate for 5 min. Add the hydrophobic ionomer DE520 (5 wt%; the solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:3) and ultrasonicate for 5 min. Finally, add 10 wt% PTFE aqueous solution and isopropanol, and perform high-speed shearing for 30 min at a shearing rate of 10,000 rpm. Its I / C ratio is 0.4, and the solid content is 2 wt%. The mass ratio of water to isopropanol is 1:1.

[0045] (2) Place the prepared slurry in an ultrasonic spraying machine and perform circular orbit ultrasonic spraying on the PEM according to the program set by the spraying machine. The spraying area is 25 cm 2 . On the side of the PEM close to the cathode, spray 0.15 mg / cm 2 , and on the cathode side of the GDL, spray 0.15 mg / cm 2 .

[0046] Example 4

[0047] A method for preparing a membrane electrode specifically includes the following steps:

[0048] (1) Preparation of the slurry on the side of the PEM close to the cathode: Mix 60 wt% Pt / C with deionized water and ultrasonically treat for 5 min. Add the hydrophilic ionomer DFPSA-2179S (10 wt%; the solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:1) and ultrasonically treat for 5 min. Finally, add isopropanol and perform high-speed shearing for 30 min at a shearing rate of 10000 rpm. Its I / C ratio is 0.8, and the solid content is 2 wt%. The mass ratio of water to isopropanol is 1:1;

[0049] Preparation of the slurry on the cathode side of the GDL: Mix 60 wt% Pt / C with deionized water and ultrasonically treat for 5 min. Add the hydrophobic ionomer DE520 (5 wt%; the solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:3) and ultrasonically treat for 5 min. Finally, add isopropanol and perform high-speed shearing for 30 min at a shearing rate of 10000 rpm. Its I / C ratio is 0.4, and the solid content is 2 wt%. The mass ratio of water to isopropanol is 1:1.

[0050] (2) Place the prepared slurry in an ultrasonic spraying machine and perform circular orbit ultrasonic spraying on the PEM according to the program set by the spraying machine. The spraying area is 25 cm 2 . On the side of the PEM close to the cathode, spray 0.15 mg / cm 2 , and on the cathode side of the GDL, spray 0.15 mg / cm 2 .

[0051] Example 5

[0052] A method for preparing a membrane electrode specifically includes the following steps:

[0053] (1) Preparation of the cathode-side slurry of PEM: 60 wt% Pt / C is mixed with deionized water and ultrasonicated for 5 min, then hydrophilic ionomer DFPSA-2179S (10 wt%; solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:1) is added and ultrasonicated for 5 min. Finally, isopropanol is added and high-speed shearing is carried out for 30 min. Its I / C ratio is 0.8, the solid content is 8 wt%, the shearing rate is 10,000 rpm, and the mass ratio of water to isopropanol is 1:1;

[0054] Preparation of the cathode-side slurry of GDL: 60 wt% Pt / C is mixed with deionized water and ultrasonicated for 5 min, then hydrophobic ionomer DE520 (5 wt%; solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:3) is added and ultrasonicated for 5 min. Finally, 10 wt% PTFE aqueous solution and isopropanol are added and high-speed shearing is carried out for 30 min. The shearing rate is 10,000 rpm, its I / C ratio is 0.4, the solid content is 2 wt%, and the mass ratio of water to isopropanol is 1:1.

[0055] (2) Place the prepared slurry in an ultrasonic spraying machine and perform circular orbit ultrasonic spraying on the PEM according to the program set by the spraying machine. The spraying area is 25 cm 2 . Among them, 0.15 mg / cm 2 is sprayed on the cathode side of the PEM, and 0.15 mg / cm 2 is sprayed on the cathode side of the GDL.

[0056] Example 6

[0057] A method for preparing a membrane electrode specifically includes the following steps:

[0058] (1) Slurry preparation: 60 wt% Pt / C is mixed with deionized water and ultrasonicated for 5 min, then hydrophilic ionomer DFPSA-2179S (10 wt%; solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:1) is added and ultrasonicated for 5 min. Finally, isopropanol is added and high-speed shearing is carried out for 30 min. The shearing rate is 10,000 rpm, its I / C ratio is 0.8, the solid content is 2 wt%, and the mass ratio of water to isopropanol is 1:1.

[0059] (2) Place the prepared slurry in an ultrasonic spraying machine and perform circular orbit ultrasonic spraying on the PEM according to the program set by the spraying machine. The spraying area is 25 cm 2 , and the total spraying loading is 0.3 mg / cm 2 .

[0060] Example 7

[0061] A method for preparing a membrane electrode specifically includes the following steps:

[0062] (1) Preparation of the cathode-side slurry of PEM: Mix 60 wt% Pt / C with deionized water and ultrasonicate for 5 min. Add the hydrophilic ionomer DFPSA-2179S (10 wt%; the solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:1) and ultrasonicate for 5 min. Finally, add isopropanol and perform high-speed shearing for 30 min at a shearing rate of 10,000 rpm. Its I / C ratio is 0.8, and the solid content is 2 wt%. The mass ratio of water to isopropanol is 1:1;

[0063] Preparation of the cathode-side slurry of GDL: Mix 60 wt% Pt / C with deionized water and ultrasonicate for 5 min. Add the hydrophobic ionomer DE520 (5 wt%; the solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:3) and ultrasonicate for 5 min. Finally, add 10 wt% PTFE aqueous solution and isopropanol and perform high-speed shearing for 30 min at a shearing rate of 10,000 rpm. Its I / C ratio is 0.4, and the solid content is 2 wt%. The mass ratio of water to isopropanol is 1:1.

[0064] (2) Place the prepared slurry in an ultrasonic spraying machine and perform circular orbit ultrasonic spraying on the PEM according to the program set by the spraying machine. The spraying area is 25 cm 2 . Spray 0.15 mg / cm on the cathode side of the PEM 2 , and spray 0.15 mg / cm on the cathode side of the GDL 2 .

[0065] Test the performance of Examples 1-7 under the test conditions of: 80 °C, 100% RH, H2 / Air.

[0066] It can be seen from Figure 1-2 that in Example 2, the interfacial resistance of the membrane electrode increases by 9% at 2 A / cm 2 , and the current density decreases by 17% at 0.6 V; in Example 3, the slurry sedimentation rate accelerates, obvious cracks appear in the catalyst layer, and the performance seriously deteriorates; in Example 4, the addition of PTFE is cancelled on the GDL side, the hydrophobicity of the electrode increases, the flooding phenomenon is serious, and the limiting current density decreases by 20%; in Example 5, the solid content is increased by 6%, the viscosity increases resulting in uneven coating, and the activity seriously deteriorates; in Example 6, the flooding phenomenon is serious, and the internal resistance meter shows performance decay at high current density. In Example 7, the loading ratio of the PEM side to the GDL side is 1:1, and the performance slightly decays at high current density.

[0067] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A hydrogen fuel cell catalyst layer slurry based on hydrophilic and hydrophobic regulation, characterized by: Includes the following: The slurry near the cathode side of the PEM includes Pt / C catalyst, deionized water, perfluorosulfonic acid ionomer solution, and isopropyl alcohol; The GDL cathode side slurry includes Pt / C catalyst, deionized water, perfluorosulfonic acid ionomer solution, PTFE aqueous solution, and isopropyl alcohol.

2. The hydrogen fuel cell catalyst layer slurry based on hydrophilic and hydrophobic regulation according to claim 1, characterized in that: In the slurry near the cathode side of the PEM, the mass ratio of the ionomer to the carbon carrier, ie, the I / C ratio, is 0.8 to 1.2; and the perfluorosulfonic acid ionomer is a hydrophilic ionomer.

3. The hydrogen fuel cell catalyst layer slurry based on hydrophilic and hydrophobic regulation according to claim 2, characterized in that: The Pt loading amount in the Pt / C is 50-70 wt %; and the mass ratio of water to isopropanol is 1:

1.

4. The hydrogen fuel cell catalyst layer slurry based on hydrophilic and hydrophobic regulation according to claim 2, characterized in that: The concentration of the hydrophilic ionomer is 8-12 wt %; the solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:

1.

5. The hydrogen fuel cell catalyst layer slurry based on hydrophilic and hydrophobic regulation according to claim 1, characterized in that: In the GDL cathode side slurry, the mass ratio of the ionomer to the carbon support, ie, the I / C ratio, is 0.3 to 0.5; and the perfluorosulfonic acid ionomer is a hydrophobic ionomer.

6. The hydrogen fuel cell catalyst layer slurry based on hydrophilic and hydrophobic regulation according to claim 5, characterized in that: The Pt loading amount in the Pt / C is 50-70 wt %; and the mass ratio of water to isopropanol is 1:

1.

7. The hydrogen fuel cell catalyst layer slurry based on hydrophilic and hydrophobic regulation according to claim 5, characterized in that: The concentration of the hydrophobic ionomer is 4-6 wt %, the solvent is water and n-propanol, and the mass ratio of water to n-propanol is 1:3; the concentration of the PTFE solution is 5-15 wt %.

8. A method for preparing a membrane electrode based on a hydrogen fuel cell catalyst layer slurry based on hydrophilic and hydrophobic regulation according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: (1) The preparation method of the slurry near the cathode side of the PEM includes: mixing Pt / C with deionized water, ultrasonically dispersing for 3 to 7 minutes, adding a perfluorosulfonic acid ionomer solution, ultrasonically dispersing for 3 to 7 minutes, and finally adding isopropyl alcohol and high-speed shearing for 20 to 40 minutes. The preparation method of the GDL cathode side slurry includes: mixing Pt / C with deionized water, ultrasonically dispersing for 3 to 7 minutes, adding a perfluorosulfonic acid ionomer solution, ultrasonically dispersing for 3 to 7 minutes, and finally adding isopropyl alcohol and PTFE solution for high-speed shearing for 20 to 40 minutes. (2) Place the prepared slurry in an ultrasonic spraying machine and perform circular orbital ultrasonic spraying on the PEM according to the program set by the spraying machine.

9. The method for preparing a membrane electrode according to claim 8, wherein: In the step (1), in the preparation method of the slurry near the cathode side of the PEM, the solid content is 1-10wt%, and the shear rate is 8000-12000rpm; in the preparation method of the slurry on the cathode side of the GDL, the solid content is 1-3wt%, and the shear rate is 8000-12000rpm.

10. The method for preparing a membrane electrode according to claim 8, wherein: In the step (2), the spraying area is 25cm 2 , PEM sprayed near the cathode side 0.1 ~ 0.3 mg / cm 2 ; GDL cathode side spraying 0.05~0.15mg / cm 2 .

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