Understanding the activity origin of oxygen-doped carbon materials in catalyzing the two-electron oxygen reduction reaction towards hydrogen peroxide generation

Abstract

Oxygen-doped carbon materials (OCM) have received a lot of attention for catalyzing the two-electron oxygen reduction reaction (2eORR) towards hydrogen peroxide generation, but the origin of their activity is not well understood. Based on density functional theory calculations, we introduce the Fukui function (f⁰), a more comprehensive and accurate method for identifying active sites and systematically investigating the activity of carbon materials doped with typical oxygen functional groups (OGs). According to the results, only ether or carbonyl has the potential to become the activity origin. The 2eORR activities of carbon materials co-doped by different OGs were then investigated, and a significant synergistic effect was discovered between different OGs (particularly between epoxy and other OGs), which might be the real active centers in OCM. To further understand the cause of the activity, the Fundamental Gap (E_g) was introduced to investigate the ability of various OCM to gain and lose electrons. The results show that the decrease in overpotential after oxygen co-doping can be attributed to the decrease in E_g. This work introduces descriptors (f⁰ and E_g) that can aid in the efficient design of catalysts and adds to our understanding of the 2eORR activity origin of OCM.

Keywords: Active site; Carbon materials; Density functional theory; Hydrogen peroxide; Oxygen functional group; Oxygen reduction reaction.