In-situ Preparation Of Catalyst Layer And Studies On Their Performances For Proton Exchange Membrane Fuel Cells

The catalytic layer（CL）is the core part of the electrode of proton exchange membrane fuel cells（PEMFCs）.It is the only site of the electrochemical reaction between anode and cathode,which has an important influence on the performance and stability of PEMFC.At present,CL is usually prepared by the method of dissociation,and the catalyst activity and utilization rate are greatly affected by the preparation process,far less than their performance in the three-electrode system,which limits the improvement of PEMFCs performance.Therefore,the electrode CL prepared by in-situ synthesis method can maintain the high activity,high utilization rate and stability of the catalyst,which is of great significance to promote the commercial development of PEMFCs.In order to improve the electrode reaction efficiency and reduce the amount of Pt in the electrode,this paper carried out the research and development of the in-situ preparation technology of PEMFCs electrode CL.A series of efficient Pt-based GDE with special morphology were prepared by in-situ growth method,and its influence on the performance and stability of PEMFCs was explored.Firstly,a simple and universal method for in-situ fabrication of Pt nanowire（Pt-NWs）on dual microporous layers（MPL）was proposed.The dual MPL consists of a hydrophobic layer and a hydrophilic layer,the hydrophobic layer is conducive to material transport,and the hydrophilic layer is conducive to the in-situ growth of Pt-NWs.The results showed that the prepared Pt-NWs uniformly grow on the surface of carbon particles and form unique CL.Meanwhile,it was applied to the cathode side of PEMFCs to optimize the dual MPL structure and Pt-NWs loading.The results showed that the optimal ratio of hydrophobic layer to hydrophilic layer is 4:1.When Pt-NWs was loaded with 0.108 mg cm^-2,the specific power density of the cell reaches 7.23 W mg _Pt^-1,which is about twice that of the commercial Pt/C cell(Pt loading was 0.2 mg cm^-2).In addition,the in-situ Pt-NWs electrode had better stability,indicating that in-situ preparation of Pt-NWs electrode has a good prospect in the practical application of PEMFCs.Secondly,a small amount of commercial Pt/C particles was sprayed on the surface of MPL as the catalyst growth site,and a uniform multi-rhomboid Pt-Pd CL was synthesized on the Pt/C surface by formic acid co-reduction method,which was applied to PEMFCs.Firstly,the Pt/Pd atom ratio was investigated.The results showed that GDE-Pt₁Pd₁,GDE-Pt₁Pd₂ and GDE-Pt₁Pd₃ all showed similar multi rhombic-pyramidal structure,and GDE-Pt₁Pd₂ showed the best performance in electrochemical test.Then,the catalyst loading was optimized on the basis of a Pt/Pd atomic ratio of 1/2.The results showed that when the total loading of Pt₁Pd₂ is 0.122 mg cm^-2,the peak power density of the cell was 0.831 W cm^-2,and the peak Pt-specific power density is up to 14.243 W mg^-_Pt¹.Compared with the commercial Pt/C cell,the increase was 0.16 and 3.1 times,respectively.In addition,the stability of GDE-Pt₁Pd₂ was significantly better than that of GDE-Pt/C,which proved that the in-situ synthesis of Pt-Pd CL had a positive effect on the performance improvement and cost reduction of PEMFCs.Finally,we prepared Pt layer growth sites on MPL surface by electrochemical replacement method,and then synthesized ternary Pt Pd Ni CL on the growth sites by wet chemical reduction method,and studied its effect on the performance and stability of PEMFCs.The results showed that the catalyst uniformly grew on the surface of MPL.Compared with GDE-Pt Ni and GDE-Pd Ni,GDE-Pt Pd Ni showed the best electrochemical performance and stability,with the peak power density of 0.824 W cm^-2.After ADT test,the performance of GDE-Pt Pd Ni was only reduced by 10.19%.Furthermore,compared with the commercial Pt/C electrode,GDE-Pt Pd Ni also showed better cell performance and stability,which again demonstrates the profound significance of in-situ preparation of Pt-based CL for the commercial development of PEMFCs.