Cation Substitution in High-Entropy Layered Double Hydroxide Driving D-Band Center Tuning for Oxygen Evolution Reaction

Abstract

The development of electrocatalysts with optimized intermediate adsorption and low energy barriers is crucial for the oxygen evolution reaction (OER). In this work, the d-band center position of high-entropy layered double hydroxides (HE-LDHs) is modulated by substituting Mg2⁺ sites with Fe2+, Cu2+, Co2+, and Ni2+. It is demonstrated that the d-band center position relative to the Fermi level is modified, reaching an optimal energy in (FeCuCoNi)6Al2-LDH. The nature of the incorporated transition metals significantly influenced OH− adsorption kinetics and reduced the overpotential for OER by 55%, compared to native LDH. The stepwise substitution of Mg2⁺ by Fe2⁺ particularly induces charge carrier transfer, switching into Faradaic processes favorable to the enhancement of OER kinetics. This work provides an effective approach that allows decreasing the OER overpotential through adjusting the position of the d-band center, and suggests that d-band tuning via multication insertion can directly shift the material toward an optimal binding strength region, which underlies the observed performance.