Proton And Electron Conductor Polymer Co-stabilized Metal Catalysts Towards Oxygen Reduction Reaction

The catalyst is one of the core components for proton exchange membrane fuel cells?PEMFCs?.Although the traditional commercial Pt/C catalyst has a high oxygen reduction reaction?ORR?activity,its carbon support material is prone to suffer electrochemical oxidation under the harsh operating environment of PEMFCs,resulting in the detachment of Pt metal catalyst particles from the surface of carbon supports.Besides,the migration and agglomeration of Pt nanoparticles?NPs?also lead to the inevitable loss of electrochemical active area of Pt NPs.Therefore,the activity and lifespan of the catalyst are deteriorated.To promote the large-scale commercialization of PEMFCs,the issue of the catalyst stability of the catalyst should be addressed urgently.Based on the understanding of the mechanism of electrochemical performance attenuation for catalysts,in this work,a strategy to improve the stability by simultaneously considering the support and the metal catalyst is proposed.That is,the proton and electron conductor polymer co-stabilized Pt metal catalyst where the proton and electron conductors are perfluorosulfonic acid?PFSA?and conductive polyaniline?PANI?,respectively.For the synthesis,first,we prepare a C@PANI composite by using an in-situ polymerization to coat a conductive PANI layer onto the surface of porous carbon black?Vulcan XC-72?,where the thickness of the PANI shell is about 2.5 nm.Then,Pt colloidal nanoparticles wrapped with the PFSA?PFSA-Pt?are prepared by the ethylene glycol liquid phase reduction.After dispersing these Pt colloids onto the surface of the C@PANI support during subsequent reduction,a Pt-based catalyst co-stabilized with proton and electron conductor polymers?PFSA-Pt/C@PANI?for PEMFCs is obtain.Electrochemical characterizations show that the PFSA-Pt/C@PANI catalyst(116 mA/mg_Pt)not only has a good ORR catalytic activity,but shows a higher electrochemical stability than the commercial Pt/C catalyst after 6,000 potential cycles of CV.The ECSA and MA losses are only 28%and 37%,respectively,while for the Pt/C catalyst is up to 43%and 60%,respectively.The robust electrochemical property of the as-prepared PFSA-Pt/C@PANI catalyst can be due to the result of introducing PFSA and PANI into the catalyst.Among them,polyaniline serves as a protective shell,which can prevent the carbon support from oxidative corrosion in harsh chemical and electrochemical environments.Meanwhile,PFSA can also anchor Pt NPs on C@PANI to avoid aggregation and detachment of Pt NPs due to the increased metal-support interaction caused by the strong electrostatic attraction between PANI and PFSA with corresponding positive and negative charges.Therefore,the protective effect of PANI and the anchoring effect of PFSA co-ensure the high stability of the PFSA-Pt/C@PANI catalyst.In addition,the triple-phase boundary towards ORR catalysis can be facilitated by PFSA as proton conductor.Significantly,after coating PANI onto carbon supports?C@PANI?,most surface micropores of carbon are occupied,effectively avoiding the embedding of Pt NPs into micropores.These are beneficial to increase utilization of Pt noble metals and ORR activity.