Metal- and Site-Specific Roles of High-Entropy Spinel Oxides in Catalytic Oxidative Polymerization of Water Contaminants

Abstract

High-entropy spinel oxides (HESOs) have emerged as promising catalysts due to their multimetal interactions, compositional flexibility, and superior structural stability; however, the roles of each metal in catalytic reactions remain elusive. In addition, catalytic organic recycling via polymerization has attracted increasing attention as a sustainable strategy for wastewater treatment. Herein, we synthesized HESOs incorporating five transition metals (Fe, Co, Ni, Cr, and Mn) using a low-temperature microwave-assisted method to achieve highly dispersed metal species in nanoparticles for catalytic peroxymonosulfate (PMS) activation for organic transformation and elucidate the different metal site catalysis. Comprehensive characterizations confirmed the single-phase spinel structure, high configurational entropy, and site-selective cation distribution among the tetrahedral and octahedral sites within the HESOs. The HESOs demonstrated superior activity in PMS activation for the polymerization of bisphenol A (BPA), outperforming single metal-based oxides. Mechanistic studies revealed that BPA degradation followed a nonradical electron transfer pathway mediated by surface catalyst-PMS* complexes. The enhanced catalytic activity was attributed to the distinct roles of individual metal components at different sites: Co served as the predominant electron donor, Cr facilitated strong PMS adsorption, and Ni supported the redox cycling of Co²⁺/Co³⁺. These metal-specific contributions synergistically enhanced the PMS activation efficiency, enabling BPA removal via oxidative polymerization with minimal oxidant consumption. Overall, this work provides in-depth insights into the metal- and site-specific roles in multisite synergy of HESOs and demonstrates their innovative application in Fenton-like catalysis toward fast water decontamination in a more selective and low-chemical-consumption manner for carbon recycling.