Vacancy Promotion in Layered Double Hydroxide Electrocatalysts for Improved Oxygen Evolution Reaction Performance
Muhammad Zubair, Priyank V. Kumar, Malte Klingenhof, Bijil Subhash, Jodie A. Yuwono, Soshan Cheong, Yin Yao, Lars Thomsen, Peter Strasser, Richard D. Tilley, Nicholas M. Bedford
Abstract
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 O upon 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 O facilitated by the partial reduction of Ce 4+ to Ce 3+ 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 O reduces 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 O promoters in LDH electrocatalysts can provide insights for future catalyst design in anodic reactions.