Sulfur‐Stabilized High Entropy Oxysulfides Enable Efficient CC Bond Cleavage in Ethylene Glycol Electrooxidation for Sustainable Plastic Upcycling to Formate

The conversion of plastic waste into value‐added chemicals coupled with energy‐efficient H 2 production is a sustainable strategy for addressing environmental and energy challenges, for example, the selective electrooxidation of polyethylene terephthalate (PET)‐derived ethylene glycol (EG) to C1 products via CC bond cleavage is important for advancing PET electro‐reforming. Herein, a high‐entropy transition metal oxysulfide is synthesized through the one‐step room‐temperature incorporation of S into a high‐entropy transition metal oxide and evaluated as a catalyst for EG electrooxidation under alkaline conditions. Covalently bound S stabilizes O vacancies and high‐valence transition metal states through defect‐induced charge redistribution, enhancing lattice stability and promoting the establishment of an advantageous electronic structure. The developed catalyst is highly active, selective, and durable, achieving efficient CC bond cleavage and formic acid production with a faradaic efficiency of 84.6%. S incorporation enhances both lattice‐oxygen and adsorbed‐oxygen mechanism pathways for CC bond cleavage and accelerates hydrogen atom transfer, thereby enabling concerted formate formation. Replacing the anodic O 2 evolution reaction with EG electrooxidation markedly reduces the required cell voltage, highlighting the high–entropy oxysulfide's promise as an electrocatalyst for plastic upcycling and energy–efficient green H 2 generation.