Lattice-Oxygen-Mediated Electronic Reconstruction of High-Entropy Oxides for Durable Fenton-like Water Treatment

Abstract High-entropy catalysts offer broad compositional tunability for peroxymonosulfate (PMS)-based water treatment, yet achieving rapid, selective, and durable oxidation remains challenging because metallic bonding in high-entropy alloys (HEAs) limits electronic communication among metal sites. Here, we construct a quinary high-entropy oxide (HEO, (FeCoNiMnCu)3O4) featuring an oxygen-bridged M-O-M framework that enables local electronic coupling among neighboring metal centers. X-ray absorption spectroscopy and theoretical calculations support oxygen-mediated charge redistribution, with Hirshfeld analysis indicating 0.46e of charge transfer toward adsorbed PMS. Temperature-dependent electrochemical impedance spectroscopy reveals a substantially lower apparent activation energy for interfacial charge transfer in the HEO (0.43 eV) than in the HEA (1.15 eV). Mechanistic experiments support a predominantly nonradical PMS activation pathway involving high-valent cobalt-oxo species and singlet oxygen. The HEO achieved near-complete phenol degradation and 87.9% total organic carbon removal within 10 min, with an apparent rate constant of 0.359 min–1 versus 0.113 min–1 for the HEA. The system maintained >90% phenol removal across pH 3–11, sustained activity over 30 reuse cycles, and retained effective contaminant removal during continuous-flow operation and 50 L bench-scale treatment. These results support lattice-oxygen-mediated electronic reconstruction as a strategy for coupling efficient PMS activation with structural durability in high-entropy oxide catalysts.