Defect and interface engineering of hexagonal Fe2O3/ZnCo2O4 n-n heterojunction for efficient oxygen evolution reaction

This work aimed at constructing defective heterojunction to optimize the electronic structure and exploring the intrinsic mechanism of its excellent electrocatalytic performance. Specifically, Feδ+ is introduced through the cation exchange method using hexagonal interpenetrating twin Zn/Co-ZIFs as precursors. Then, the n-n heterojunction featuring oxygen vacancies at the biphasic interface of Fe2O3 and ZnCo2O4 is constructed through calcination. The obtained electrode for oxygen evolution reaction (OER) only requires 261 mV overpotential to achieve a current density of 10 mA cm−2, and shows exceptional stability at high current density, lasting for 50 h. Density functional theory calculations confirm that the construction of heterojunction can effectively optimize the d‐band center and improve the adsorption of the active center on oxygen-containing intermediates, thus optimizing the Gibbs free energy of the OER. This study provides inspiration and interface engineering strategy for the design of highly active catalysts, and enhances our understanding of the OER mechanism. [Display omitted] •The novel hexagonal hollow structures increased specific surface area and facilitated exposure of active sites.•More oxygen vacancies are introduced by Feδ+ exchange which improves the intrinsic activity of the active site.•N-n heterojunction interface induces spontaneous charge transfer and effectively optimizes the surface electronic state.•DFT calculations confirmed that heterojunctions with defects can effectively optimize the Gibbs free energy of the OER.