An Oxygen‐Defect‐Induced Unsaturated Coordination Strategy Boosts High‐Selective PET Upcycling via Suppressing Oxygen Evolution

Electrochemical upcycling of polyethylene terephthalate (PET) plastics coupled with hydrogen production offers a sustainable pathway for carbon reutilization and energy sustainability. However, PET‐derived ethylene glycol electro‐oxidation reaction (EGOR) in alkaline conditions inevitably competes with oxygen evolution reaction (OER) due to enhancing OH − utilization for OER under industrially relevant high‐current conditions, reducing electrolysis efficiency and degrading catalyst stability. In this study, we precisely regulate oxygen‐defect concentration to construct an unsaturated CoFeO x (OH) y /CFP catalyst, achieving 93% ± 2% Faradaic efficiency (FE) for formic acid and over 700 h of stability. In situ characterizations and theoretical calculations show that oxygen defects tune the surface electronic structure and promote the timely consumption of electrochemically generated MO x (OH) y species by EG preventing the excessive accumulation of high‐valence species and suppressing OH − evolution into oxygenated OER intermediates. By balancing MO x (OH) y formation with its spontaneous reaction with EG, OH − utilization toward EGOR is enhanced, enabling efficient OER suppression at high anodic potentials. Furthermore, a large‐scale three‐cell electrolyzer (300 cm 2 per piece) achieves 17.4 A at 3 V with nearly 100% FE for hydrogen production, reducing energy consumption by > 21.05% compared with overall water splitting. This work provides mechanistic insights and a practical strategy for industrial PET upcycling integrated with low‐energy hydrogen production.