Synthesis Of Different Atoms Doped Porous Carbon Materials As Efficient Electrocatalyst For Oxygen Reduction Reaction

Fuel cells have been of continuous interest in the field of clean energy owing to their high power density and low pollutant emissions.Platinum?Pt?or Pt-based precious metal catalysts have been widely used for promoting the electrochemical oxygen reduction reaction?ORR?on the electrode of fuel cell.Nevertheless,though Pt-based catalysts exhibit high efficiency for ORR,their high cost and low tolerance to fuel crossover reduce their potential in practical use and hinder the large-scale commercialization of fuel cells.In recent years,various Pt-free catalysts have been developed,such as transition metal oxide,porous carbon,graphene and their composite.Among them,porous carbon catalysts have drawn considerable interests owing to their evident advantages such as low cost,tunable catalytic activity as well as high thermal/chemical stability.Therefore,in recent years,intensive efforts have been devoted to developing novel porous carbons with enhanced catalytic performance.First,a novel type of N,S,P-codoped carbons with varied nanostructures is investigated as efficient and stable electrocatalyst for the oxygen reduction reaction?ORR?.The carbon catalysts were prepared using poly?cyclotriphosphazene-co-4,4'-sulfonyldiphenol??PZS?nanospheres as single precursors through a pyrolysis procedure with or without presence of blowing agent such as melamine.The as-prepared microporous carbon nanospheres NSP-PC-1 with high surface area(967 m² g^-1)exhibits a significantly enhanced ORR catalytic activity compared to the solely N-doped counterpart,suggesting the remarkable contribution of additional S,P doping on the ORR performance.Moreover,the mesoporous carbon nanosheet NSP-PC-2 with moderately high surface area(613 m² g^-1)and comparable NSP compositions shows greatly improved ORR catalytic activity relative to that of NSP-PC-1,which is even slightly superior to that of commercial Pt/C catalyst.The excellent performance of NSP-PC-2 is mainly attributed to the synergistic effect of the N,S,P codoping as well as its structural advantages.We also developed a series of transition metal?Fe,Co?and N-codoped porous carbon materials MPc-CMPs?M=Co,Fe?.These carbons were prepared through a pyrolysis process using iron or cobalt phthalocyanine?FePc or CoPc?-based covalent organic polymer?COP?as precursors.The as-prepared carbons MPc-CMPs?M=Co,Fe?exhibit very good catalytic performance.In particular,FePc-CMP-1 even performed better than the commercial Pt/C catalyst.This can be attributed to its Fe,N-codoping,high specific surface area and hierarchical porous structures,which result in the presence of sufficient catalytic centers and facilitate proton transfer,thus enhancing the ORR process.In addition,all these carbon catalysts showed high stabilities in alkaline environment,higher than that of the commercial Pt/C catalyst.For comparison,control catalyst CMP-2was prepared by removing Fe from the FePc-CMP-1 with acid.The inferior catalytic performance of CMP-2 might indicate that Fe-doping plays an important role during the catalyzing ORR process.