Solid-acid-mediated electronic structure regulation of electrocatalysts and scaling relation breaking of oxygen evolution reaction.

• The solid-acid structure was introduced on surfaces of Co 3 O 4 and CoNiFeO x. • The SO 4 2− modification triggers Co4+ and intermediate spin state of Co3+ (t 2 g 5 e g 1). • Additional adsorption of SO 4 2− breaks adsorption-energy scaling relation. • CoNiFeO x -SO 4 exhibits superior performances in OER. Adjusting the electronic structure of electrocatalyst active sites can optimize the adsorption of intermediates to boost the kinetics of oxygen evolution reaction (OER), while this modulation is limited by adsorption-energy scaling relations of three intermediates (*OH, *O and *OOH). This work introduced the solid-acid structure into electrocatalysts through surface bonding SO 4 2− (like Co 3 O 4 and CoNiFeO x). DFT calculations reveal the essence of solid acid modification is that triggers the production of Co4+ and intermediate spin Co3+ (t 2 g 5 e g 1), then lifts metal d-band level and oxygen p-band level. Notably, the hydrogen bonding between SO 4 2− group and ∗OOH provides additional adsorption contribution, thereby breaking the adsorption-energy scaling relation of OER. Modified by SO 4 2−, the CNF-SO 4 shows remarkably high performance with overpotential of 231 mV (at 10 mA cm-2) and low Tafel slop of 33.8 mV·dec-1. This work provides an effective solid-acid-mediated strategy for electronic structure regulation and adsorption-energy scaling relation breaking in OER. [ABSTRACT FROM AUTHOR]