Dissolved Fe species enable a cooperative solid–molecular mechanism for the oxygen evolution reaction on NiFe-based catalysts

Abstract

The oxygen evolution reaction is a key process in many energy technologies, but improving its efficiency remains challenging due to the energy scaling relationships that limit the reaction kinetics on conventional single-active-site solid catalysts. Here we report a cooperative solid–molecular mechanism for oxygen evolution on NiFe-based hydroxide electrocatalysts. By identifying the critical interfacial species and understanding their dynamics, we find that molecular FeO₄²⁻ species, derived from the dissolution of Fe from the solid catalyst, act as molecular co-catalysts that participate in the critical O–O bond-formation step along with solid sites. This synergistic mechanism, involving both solid and molecular active species, circumvents the typical scaling limitations observed for solid catalysts alone. Our findings reveal an unconventional solid–molecular mechanism that governs electrocatalysis at the solid–liquid interface and suggest a strategy for transcending scaling constraints through cooperative multi-site catalysis.