Steering the oxygen reduction reaction pathways of N-carbon hollow spheres by heteroatom doping

Abstract

An original strategy was reported to manipulate ORR selectivity of N-doped hollow mesoporous carbon spheres (N-HMCS) via heteroatom (P and S) doping. Heteroatom doping can not only modulate electronic structure of N-HMCS and proportion/configuration of doped N, but also regulate ORR pathway. Specifically, rich-graphitic N sites and electron-rich C–P bond domains in N,P-HMCS act as electron donors, making *OOH more unstable and easier to desorb into H2O2. This severely distorts the sp2 lattice of graphene, catalyzing a two-electron ORR synergistically. Conversely, a strong interaction between electron-deficient C–S bond domain and *OOH intermediate due to the introduction of highly electronegative S hinders the desorption of *OOH, leading to the breakage of the O–O bond and promoting four-electron ORR along with the rich-pyridinic N receptor site. The reaction activity and kinetics mechanism present a positive correlation with proportion of graphitic N, revealing graphitic N is the primary active site with a much faster electron transfer capacity.