Electrochemical Upcycling of Polyethylene Terephthalate: Catalyst Design, Reaction Mechanisms, and Integrated Paired Electrolysis

Abstract

Polyethylene terephthalate (PET) waste has become a persistent global environmental challenge, motivating the development of sustainable recycling and valorization strategies beyond conventional mechanical and thermochemical routes. Electrochemical PET upcycling has recently emerged as a promising alternative, enabling the selective oxidation of PET-derived ethylene glycol (EG) into value-added C1 and C2 products. This review provides a comprehensive overview of the reaction pathways, catalyst design principles, and integrated paired-electrolysis strategies for EG electro-oxidation (EGOR). We summarize advances in electrocatalysts spanning noble metals, transition-metal compounds, metal-organic frameworks, organic catalysts, and heterojunction architectures. Beyond anodic EGOR, we discuss energy-efficient paired electrolysis configurations coupling EGOR with cathodic reactions such as hydrogen evolution, two-electron oxygen reduction to H2O2, CO2 reduction, and nitrate reduction, highlighting their roles in lowering cell voltage and enabling co-production of value-added chemicals. Mechanistic insights derived from in situ spectroscopy and theoretical calculations are critically examined to elucidate active-site evolution, intermediate stabilization, and reaction-depth control. Finally, key challenges and future opportunities are identified, including selectivity control at industrial current densities, impurity tolerance, product separation, and standardized testing protocols. This review aims to provide a mechanistic and system-level framework to guide the rational design of selective, energy-efficient, and scalable electrochemical PET upcycling technologies.