Vacancy Promotion in Layered Double Hydroxide Electrocatalysts for Improved Oxygen Evolution Reaction Performance

Layered double hydroxides (LDHs) are promising catalysts for the oxygen evolution reaction (OER) given their modular chemistry and ease of synthesis. Herein, we report a facile strategy for inclusion of oxygen vacancies (V_O) using Ce as a promoter in Co-Ni LDHs that significantly enhances the activity for OER. In situ X-ray absorption spectroscopy (XAS) uncovers an increase in octahedral Co sites and V_Oupon addition of Ce that promotes the transformation of the LDH into an oxyhydroxide-reactive phase more readily. The presence of an OER-active oxyhydroxide phase along with the generation of V_Ofacilitated by the partial reduction of Ce⁴⁺to Ce³⁺under oxidizing conditions results in a better electrochemical activity of Ce-doped electrocatalysts. Density functional theory calculations further corroborate the in situ XAS experimental findings by showcasing that the presence of both Ce and V_Oreduces the free-energy barrier of the rate-limiting OH∗ deprotonation step during OER. This work showcases how an enhanced understanding of the role of V_Opromoters in LDH electrocatalysts can provide insights for future catalyst design in anodic reactions.