Cation and vacancy engineering in high-entropy layered double hydroxides for water oxidation
Layered double hydroxides (LDHs) are promising electrocatalysts for the oxygen evolution reaction (OER), yet their practical application remains limited by poor electrical conductivity and sluggish reaction kinetics. In this work, we synthesize three high-entropy LDHs (HELDHs) featuring a hierarchical architecture of microspheres assembled from ultrathin nanosheets, via a simple hydrothermal method using a combination of low-cost, catalytically active transition metals (Fe, Co, Ni, Mn, Zn, Cu, and Cr). Among them, the FeCoNiMnZn HELDH exhibits outstanding OER performance, requiring an overpotential of only 306 mV to reach a current density of 100 mA cm−2. Notably, during 200 h of continuous operation, the device exhibits a stable and, in some cases, increasing current output. This exceptional activity is attributed to the formation of abundant cation vacancies, induced by Zn leaching, which enhance the intrinsic catalytic properties by optimizing the adsorption energies of key OER intermediates. Density functional theory calculations further validate that these vacancies modulate the electronic structure and lower reaction barriers, underscoring the effectiveness of cation-vacancy engineering in high-entropy systems for efficient and durable water oxidation catalysis. The optimized catalyst was further evaluated as the air cathode in a zinc–air battery, demonstrating practical electrochemical performance.