Origins of high onset overpotential of oxygen reduction reaction at Pt-based electrocatalysts: A mini review

Abstract Even at the best oxygen reduction reaction (ORR) catalyst, i.e., Pt-based materials, the ORR current is observed only below 1.0 V RHE , indicating an onset overpotential higher than 0.20 V (0.25 V at pure Pt). Rational design of more active ORR catalysts hinges on correct understanding of the origins of this high onset overpotential, which is a topic of controversy for decades. In this contribution, major viewpoints in the literature are recapitulated, a recent framework compiling several factors into a unified picture is introduced, and perspectives for more comprehensive analysis in future are given.