The nature of synergistic effects in transition metal oxides/in-situ intermediate-hydroxides for enhanced oxygen evolution reaction

Abstract

Oxygen evolution reaction is highly important for hydrogen production via water splitting but requires ∼0.22 V onset overpotential, resulting in at least 15% extra energy consumption even utilized with the benchmark hetero-doped transition-metal hydroxide catalysts. The lack of fundamental understanding on catalyst behaviour and on synergistic mechanisms limit the breakthrough for material design. Here, we systematically summarise a variety of investigations and arguments on the mechanism from the microscale (optimal octahedral intermediate with six M−O coordination) to atomic scale (the active site behaviour). The electron–orbital scale ( e g ) is further described for the intrinsic OER activity. The synergistic effect may also lead to a short-cut pathway of lattice-oxygen-mediated mechanism to achieve a smaller overpotential. This review provides a theoretical reference for the design of advanced catalysts.