Bimetal Leaching Induced Reconstruction of Water Oxidation Electrocatalyst for Enhanced Activity and Stability

Abstract

Surface reconstruction inevitably occurs during pre-catalysis for the oxygen evolution reaction (OER); however, obtaining OER electrocatalysts with high performance and stability remains a challenge. In this study, we have developed a bimetallic leaching-induced surface reconstruction strategy to fabricate efficient electrocatalysts for water oxidation. Microcolumn arrays consisting of α-CoMoO₄, K₂Co₂(MoO₄)₃, Co₃O₄, and CoFe₂O₄ four-phase oxides were integrated as pre-catalyst by a hydrothermal, ion-exchange, and subsequent annealing process. In situ Raman spectroelectrochemical and ex situ X-ray diffraction (XRD) studies revealed that the rapid dissolution of the unstable component K₂Co₂(MoO₄)₃ triggered the adaptive leaching of Mo and K, which accelerated the transformation of the surface-enriched α-Co(OH)₂ to the active phase of CoOOH at low voltage. Furthermore, the stable CoFe₂O₄ component couples the reconfigured new phase CoO with the amorphous layer CoOOH to form a compact hierarchical structure of CoFe₂O₄@CoO@CoOOH, which plays the role of a nanofence and effectively prevents the catalyst from over-reconstruction, thus achieving excellent catalytic stability. This work provides a novel idea for designing OER catalysts with excellent activity and stability at high current densities.