Degradation Mechanism and Enhancing Strategies of Oxygen Reduction Reaction Catalyzed by Carbon-Based Metal Free Catalysts in Acidic Solution

摘要

Carbon-based metal free catalysts (CMFCs) are far away from commercialavailability mainly attributed to their poor oxygen reduction reaction (ORR)performance in acidic environment with the causes remaining obscure. Byinvestigating the heteroatoms (N, B, P, S, Se, and Te)-doped reduced grapheneoxides, the degradation mechanism of acidic ORR performance ofCMFCs is found to be correlated with the oxygen-baring defects in the carbonsp2 lattice, which exhibit overpotentials as low as 0.44 V but weak trappingcapabilities for oxygen molecules. These findings not only revise the previouslyreported strategy of modeling the active sites in the basal plane of CMFCsbut also highlight the connections between those active sites and the triplecoordinatedVIA group elements (XC_3). Further calculations demonstratethat the XC_3 dimer can efficiently enhance the acidic ORR performance andthe 2D trigonal carbon-chalcogenides C_6X (X = S, Se, and Te) are accordinglydesigned toward acidic ORR, which contain homogeneously distributed basalplane active sites and exhibit low overpotentials but strong trapping capabilitiesfor oxygen molecules. This work will help to cease the debates on theactive sites in CMFCs for ORR in both acidic and alkaline solutions and toopen a new avenue to design CMFCs independent on doping strategy.