Deciphering the Synergy of Multiple Vacancies in High-Entropy Layered Double Hydroxides for Efficient Oxygen Electrocatalysis

Abstract

Layered double hydroxides (LDHs) hold the promise of designing efficient and long-lived electrocatalysts for alkaline oxygen evolution reaction (OER), yet control of their activity and durability at ampere-scale current densities remains a challenge. Here, a high-entropy LDH anode integrating multiple metal and oxygen vacancies is reported that achieves superior and robust OER under industrial conditions. The molar ratio of Ni:Cr:Co:Zn:Fe in high-entropy LDHs engineers the electronic structure via the cocktail effect, yielding more high-valent metal ions that promote the electrochemical restructuring. Using various operando characterizations, the generation of γ-NiOOH active-phase on a high-entropy LDH surface is identified, triggering the oxygen-vacancy-site mechanism (OVSM). Importantly, a volcano relationship is found between intrinsic OER activity (overpotential value) and the local coordination structure of Ni active centers (matching with the ΔG_*OH). The integration of multiple metal and oxygen vacancies significantly optimizes the adsorption-free energy of oxygen-containing intermediates that are anchored at Ni active sites, boosting the OVSM. Accordingly, the developed Ni_0.15Cr_0.15Co_0.4Zn_0.1Fe_0.2-LDH@NF achieves 1 A·cm⁻² at 1.81 V and enables stable operation over 300 h in anion exchange membrane water electrolyzer. These findings elucidate the synergistic effects of multiple vacancies in high-entropy LDH electrocatalysts and enlighten the vacancy engineering for designing high-efficiency OER catalysts.