Surface chemical reconstruction of hierarchical hollow inverse-spinel manganese cobalt oxide boosting oxygen evolution reaction

Abstract

Inverse-spinel manganese cobalt oxide (MnCo2O4) is an active and stable electrocatalyst towards oxygen evolution reaction (OER) in alkaline medium, but the room still remains for improving its activity owing to the limited electronic conductivity and catalytically active sites. Herein, we propose effective and novel cerium (IV) oxide (CeO2)-induced surface chemical reconstruction strategy to optimize the OER electrocatalytic performance of inverse-spinel MnCo2O4. To reach this aim, a MnCo2O4/CeO2 heterostructure is designed and synthesized through a facile and effective zeolitic imidazolate framework (ZIF)-derived method, which not only successfully implements the surface chemical reconstruction of MnCo2O4 including: (i) the charge redistribution modulating the electronic structure and (ii) the interface reconstruction creating more oxygen vacancies, but also endows MnCo2O4/CeO2 with hierarchical hollow architecture that further extends catalytically active sites. Benefiting from the surface chemical reconstruction triggered structure and composition advantages, the as-synthesized MnCo2O4/CeO2 presents the reduced overpotentials (276 mV at 10 mA cm−2; 390 mV at 50 mA cm−2), improved kinetics (87 mV dec−1), low activation energy (Ea = 48.8 kJ mol−1) and robust long-term stability, which exceeds benchmark RuO2 and single MnCo2O4 catalysts. Density functional theory (DFT) calculations validate obvious changes for the electronic structure of MnCo2O4 and the increased d-band center of active Co atom after the surface chemical reconstruction, thus optimizing the binding strength of reaction intermediates during the OER. It is believed that this work gives references to the understanding and design of highly active heterojunction electrocatalysts for water oxidation.