Vacancy Promotion\nin Layered Double Hydroxide Electrocatalysts\nfor Improved Oxygen Evolution Reaction Performance

Abstract

Layered double hydroxides (LDHs) are promising catalysts\nfor the\noxygen evolution reaction (OER) given their modular chemistry and\nease of synthesis. Herein, we report a facile strategy for inclusion\nof oxygen vacancies (V_O) using Ce as a promoter in Co–Ni\nLDHs that significantly enhances the activity for OER. In situ X-ray\nabsorption spectroscopy (XAS) uncovers an increase in octahedral Co\nsites and V_O upon addition of Ce that promotes the transformation\nof the LDH into an oxyhydroxide-reactive phase more readily. The presence\nof an OER-active oxyhydroxide phase along with the generation of V_O facilitated by the partial reduction of Ce⁴⁺ to\nCe³⁺ under oxidizing conditions results in a better electrochemical\nactivity of Ce-doped electrocatalysts. Density functional theory calculations\nfurther corroborate the in situ XAS experimental findings by showcasing\nthat the presence of both Ce and V_O reduces the free-energy\nbarrier of the rate-limiting OH* deprotonation step during OER. This\nwork showcases how an enhanced understanding of the role of V_O promoters in LDH electrocatalysts can provide insights for\nfuture catalyst design in anodic reactions.