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

The d‐band center position of layered double hydroxide is adjusted via multication insertion in the octahedral site. The optimal position of the d‐band, near the Fermi level, enhances OER performance through optimal OH− adsorption kinetics, resulting in a 55% reduction in overpotential compared to the native catalyst. 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. The d-band center position of layered double hydroxide is adjusted via multication insertion in the octahedral site. The optimal position of the d-band, near the Fermi level, enhances OER performance through optimal OH − adsorption kinetics, resulting in a 55% reduction in overpotential compared to the native catalyst. 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 Mg 2 ⁺ sites with Fe 2+, Cu 2+, Co 2+, and Ni 2+. It is demonstrated that the d-band center position relative to the Fermi level is modified, reaching an optimal energy in (FeCuCoNi) 6 Al 2 -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 Mg 2 ⁺ by Fe 2 ⁺ 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. Advanced Science, EarlyView.