Carbon-based single atom catalysts for tailoring the ORR pathway: a concise review

Abstract

Carbon-based single-atom catalysts (C-SACs), featuring a flexible, well-defined atomic geometry and superior electrical conductivity, have experienced a rapid development in the last decade and provided unique opportunities in selective oxygen reduction reaction (ORR) electrocatalysis via a direct 4e⁻ pathway or an alternative 2e⁻ pathway for sustainable energy conversion and chemical synthesis. This concise review summarizes recent experimental efforts aimed at tailoring selectivity and activity, and deriving progressive guidelines for catalyst design. First, the current exploration and development of synthetic methodologies of diverse C-SACs for the ORR are briefly outlined. Then we present a key overview of structure-dependent catalytic selectivity and activity properties, in particular emphasizing the microenvironment modulation of single-atom active sites from the aspects of regulating the central metal atoms, coordination environment and support properties. Besides, the dual active site enabled synergistic catalysis for breaking the conventional scaling relation is also highlighted. Finally, the current remaining challenges in C-SACs for the ORR and related perspectives are proposed to shed some light on the further developments toward industrialization in the future.