High-Entropy MnFeCoNiZn-ZIF Couples Interfacial Hole Transfer with Water Oxidation Kinetics in Metal Oxide Photoanodes

Abstract

Photoelectrochemical water oxidation is constrained by inefficient interfacial hole transfer and sluggish oxygen evolution kinetics in semiconductor photoanodes. Here, a high-entropy MnFeCoNiZn zeolitic imidazolate framework (HEZ) cocatalyst was constructed on BiVO4 by in situ potentiostatic electrodeposition. The ultrathin, structurally disordered HEZ layer integrates compositionally diverse metal sites with an electronically coupled semiconductor/cocatalyst interface. Raman and X-ray photoelectron spectroscopy reveal pronounced interfacial electronic redistribution and valence-state regulation of the multimetallic centers, while photoluminescence and modulated photocurrent/photovoltage measurements reveal reduced radiative recombination and accelerated interfacial hole transfer. Density functional theory calculations further show that Zn incorporation into MnFeCoNi-ZIF lowers the free-energy requirement of the key *O-to-*OOH step from 1.28 to 0.95 eV and produces a more balanced oxygen-evolution free-energy profile. Consequently, HEZ-BiVO4 delivers a photocurrent density of 6.23 mA cm–2 at 1.23 V versus the reversible hydrogen electrode, an applied-bias photon-to-current efficiency of 1.91%, a bulk charge-separation efficiency of 99.6%, and a surface charge-injection efficiency of 95%. The photoanode retains 94% of its initial photocurrent after 10 h. Extension of HEZ modification to Fe2O3 and WO3 demonstrates a transferable strategy for coupling interfacial charge management with multimetallic water-oxidation catalysis.