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 H-2 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 (O-v) 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 H-2/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 O-v-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 (R-ct = 0.7336). Theoretical calculations further confirm that the excellent electrochemical activity strongly corresponds to the lower d-band center of active sites on the O-v-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.