N,F?Codoped Microporous Carbon Nanofibers as Efficient Metal?Free Electrocatalysts for ORR

摘要

Currently,the oxygen reduction reaction(ORR)mainly depends on precious metal platinum(Pt)catalysts.However,Pt-based catalysts have several shortcomings,such as high cost,scarcity,and poor long-term stability.Therefore,development of e cient metal-free electrocatalysts to replace Pt-based electrocatalysts is important.In this study,we successfully prepared nitrogen-and fluorinecodoped microporous carbon nanofibers(N,F-MCFs)via electrospinning polyacrylonitrile/polyvinylidene fluoride/polyvinylpyrrolidone(PAN/PVDF/PVP)tricomponent polymers followed by a hydrothermal process and thermal treatment,which was achieved for the first time in the literature.The results indicated that N,F-MCFs exhibit a high catalytic activity(Eonset:0.94 V vs.RHE,E1/2:0.81 V vs.RHE,and electron transfer number:4.0)and considerably better stability and methanol tolerance for ORR in alkaline solutions as compared to commercial Pt/carbon(Pt/C,20 wt%)catalysts.Furthermore,in acidic media,N,F-MCFs showed a four-electron transfer pathway for ORR.This study provides a new strategy for in situ synthesis of N,F-MCFs as highly e cient metal-free electrocatalysts for ORR in fuel cells.