▎ 摘　　要

A single-atom site catalyst for direct four electron oxygen reduction reaction (ORR) is identified where selenium (ultrasmall amount of Se, less than or similar to 1 at. %) is the active center that couples reduced graphene oxide (rGO) sheets. This metal-free catalyst is found to be undergoing ORR through the direct four-electron pathway in alkaline medium, similar to platinum, whereas rGO prefers a two-electron path, and the experimental observation is correlated with theoretical study. The role of Se-like elements in graphene, which have similar electronegativity as carbon, is unraveled with a detailed density functional theory-based analyses.