ZIF-67-Derived CoFe2O4/NiCo2O4@NC/CC with Oxygen-Enriched Vacancy for High-Performance Electrocatalyst toward Oxygen Evolution Reaction

Oxygen evolution reaction (OER) impedes the electrochemical water splitting for H2 production, ascribing to the depressed kinetics of the four proton-coupled transfer process. Transition metal oxides, especially bimetallic oxides, have been proven to be promising OER electrocatalysts due to their part unoccupied d-band characteristics. More interestingly, oxygen vacancies (Ov) easily constructed in transition metal oxides can modulate the electron structures and thereby boost the OER performance. However, most synthesized processes involving oxygen vacancy engineering, such as atom dopant, chemical/electrochemical reduction, and H2/Ar-dependent calcination, are energy-intensive and time-consuming, largely hampering their commercial applications. Herein, we suggest a simple and facile strategy for fabricating double spinel oxides with abundant oxygen vacancies by calcinating Ni/Fe@ZIF-67/CC precursor under a nonoxidation condition. The obtained Ov-CF1N2O@NC/CC-550 with vast oxygen vacancies exhibits excellent OER performance, representing a lower overpotential of 185 mV at 10 mA cm–2, smaller Tafel slope of 47.3 mV dec–1, as well as faster interface reaction kinetics (Rct = 0.7336). Theoretical calculations further confirm that the excellent electrochemical activity strongly corresponds to the lower d-band center of active sites on the Ov-CoFe2O4 (311) model and decreased reaction Gibbs energy barrier. The work might shed light on oxygen vacancy engineering via a simple and facile strategy and inspire a smart design of multimetallic oxide electrocatalysts with high OER performance.