Heteroatoms on Pentagon: Clarifying the Activity Origin of the Acidic Oxygen Reduction

Metal-free oxygen reduction reaction (ORR) catalysts have been intensively studied during the past decade. For heteroatoms modified carbon materials, the influence of heteroatoms on the ORR is still elusive. Herein, density functional theory (DFT) simulations were firstly used for better understanding the role of heteroatoms in catalyzing the ORR. As a model catalyst, graphene with pentagon (C5) defect was selected for studying the effect of heteroatoms in tuning the acidic ORR activity. Both theoretical and experimental results show that the N and S co-doped graphene without pentagons shows very poor ORR performance; however, in the presence of certain types of defects such as C5, the substitution of N and S to C atoms could greatly enhance the acidic ORR activity of the resulting sample, implying the essential role of defects for the ORR. This work clarifies that heteroatoms themselves show very limited contributions on the ORR, but they are powerful in tuning the electronic structures of defects for high ORR activity.