Synthesis Of Hierarchical Porous Graphene Supported Pt Catalyst For PEM Fuel Cells

With the advantages of higher efficiency of converting chemical energy to electric energy,environmentally friendly property,faster start-up,and lower operating temperature,proton exchange membrane fuel cells(PEMFC)have attracted more and more attentions,especially in the field of new energy technology.To enhance the proton conduction and decrease the membrane resistance,it is essential for PEMFC to get humidified properly.However,the humidification could also cause bad effect on the fuel cell performance in high-current region.In the high-current region,the rate of water generation increases while the excess liquid water fails to be expelled in time.As a result,some of the active sites of cathode catalysts would be blocked,leading to unstable performance of fuel cells.Besides water management,PEMFC are also faced with problems that cathode catalysts show low stability and short longevity.One important factor affecting the stability is the stability of adopted carbonaceous supports.Carbon corrosion can not only lead to the separation between Pt particles and supports,it can also cause the agglomeration of Pt particles.Consequently,the electrochemical active area and catalytic activity of catalysts will decrease significantly.This work focused on the synthesis of hierarchical porous graphene-like rods(HPGR),which has high electrochemical surface area,excellent electrical conductivity and remarkable hydrophobicity,and the application of HPGR in PE-MFC was also in depth studied.On one hand,we prepared the membrane electrode assembly(MEA)by mixing the hydrophobic HPGR with commercial Pt/C and applied it on fuel cell to decrease the negative effect of water flooding.On the other hand,we applied the HPGR as catalyst support to synthesize the cathode catalyst Pt/HPGR which had high catalytic activity and support stability,which were confirmed by rotating disk electrode(RDE)measurements and MEA tests.The main research was listed in the contents below:Chapter 1:The basic structure and unique advantages of PEMFC were briefly summarized,then we pointed out the water flooding and carbon corrosion that might slow down the development of PEMFC.In the end,we put out the subject basis and research significance.Chapter 2:The synthesis of HPGR was introduced.We prepared the MEAs by mixing HPGR and commercial 20 wt%Pt/C and tested the fuel cell performance under high relative humidification condition.Compared with pure Pt/C without HPGR,the composite catalysts showed much better catalytic activity,indicating that the introduction of hydrophobic HPGR could decrease water flooding effectively.Chapter 3:We adopted HPGR and Vulcan XC-72R as supports and prepared the corresponding catalysts Pt/HPGR and Pt/XC-72 using solvothermal method,then we investigated the electrochemical activity and support stability of Pt/HPGR,Pt/XC-72 and Pt/C with electrochemical workstation.RDE measurements showed that the active area and mass activity of Pt/HPGR remained basically unchanged after accelerated stress tests(AST),while Pt/XC-72 and Pt/C showed severe carbon corrosion.Chapter 4:We further evaluated catalytic activity and support stability of the catalysts with fuel cell test system.We prepared MEAs with different cathode catalysts and tested the fuel cell performance before and after the AST.Not surprisingly,the Pt/HPGR exhibited much superior corrosion resistance,which was in accordance with the observation from RDE measurements.Chapter 5:We summarized the research work and put forward some prospects about the application of HPGR in fuel cells.