The Preparation And The Oxygen Electroreduction Performance Of Porous Doped Graphene-like Carbon Materials

Proton exchange membrane fuel cell(PEMFC)is a kind of very potential energy conversion system.Since the sluggish kinetic process of the oxygen reduction reaction in the cathode.High performance ORR catalyst is strongly needed.To date,Pt based catalysts are still the most widely used ORR catalysts,however,their high cost also seriously prevent their commercialization.Therefore,developing low-cost and high-performance ORR catalyst to substitute traditional Pt-based catalyst will be of great significance for the commercialization of PEMFC.Among the currently available ORR catalytic materials,carbon-based catalysts have become one of the hottest research directions due to their relative high ORR performance,low cost,extensive sourse.Unfortunately,carbons still fail to meet the practical demands.In this paper,different compositions of porous doped graphene-like ORR catalysts were prepared by polymerization,doping,pyrolysis and other processes,and their catalytic properties were studied.(1)Uniform nitrogen and sulphur co-doped hollow carbon nanospheres with an ultra high surface area(1060 m2﹒g-1)were fabricated by using polyacrylonitrile and sulphur as the precursors.The catalyst exhibits outstanding ORR performance,excellent stability,methanol tolerance,as well as high selectivity toward four-electron catalytic path.By analyzing the effects of sulphur addition,we found that the sulphur addition is crucial for the formation of uniform nanospherical morphologies,as well as highly porous structures and high surface areas.Besides,sulphur addition was also found to be able to modify catalysts’ atomic compositions effectively by increasing total and pyridinic N contents while reducing oxidized N contents.The sulphur addition induced unique features in catalysts’ structures and compositions,we believed,should be the main origins to our catalyst’s outstanding ORR performance.(2)A N,S codoped porous graphene-like catalyst was obtained by using polyacrylonitrile,sulfur as the precursors,with zinc oxide as the templates.The catalyst showed excellent ORR performance in alkaline media,with a half-wave potential 32 m V more positive than that of commercial Pt/C catalyst.In addition to excellent ORR performance,the catalyst also exhibited outstanding methanol tolerance,stability,as well as high catalytic efficiency.By studying the relationship among catalyst’s structures,compositions and its catalytic performance,we found that the unique compositions,morphologies and porous structures induced by sulfur addition should be the origin to the catalyst’s high ORR performance.(3)A N and P co-doped,high surface area(1057.9 m2﹒g-1)network was fabricated by using polyacrylonitrile and red phosphorous as the precursors.The catalyst exhibits outstanding ORR performance,which can be superior to a commercial Pt/C catalyst,with a half-wave potential 35 m V more positive.In addition to high ORR performance,our catalyst also exhibits remarkable methanol tolerance,outstanding stability,as well as high selectivity of four-electron path.Moreover,we also found that moderate P introduction can significant modify catalysts N compositions,as well as porous structures,which,we suggest,should be responsible for the catalyst’s outstanding performance.