Electrochemical Upcycling of Plastic Waste: A Systematic Review of Catalyst Development, Reactor Engineering and Scale-Up Pathways

This systematic review examines the emerging field of electrochemical upcycling as a route for converting plastic waste into value added chemicals, fuels, and polymer derived intermediates. The review draws on recent experimental and demonstration studies reported from 2021 through 2025, with emphasis on systems that provide quantitative electrochemical performance data, reactor information, and technoeconomic or life cycle evidence. Across the literature, electrochemical upcycling is shown to offer a flexible platform for transforming major waste plastics, particularly polyethylene terephthalate, polyethylene, polypropylene, polystyrene, and mixed plastic streams, through anodic oxidative cleavage, cathodic reductive fragmentation, mediated electrolysis, electroreforming, and paired electrolysis. The manuscript synthesizes current knowledge on catalyst design, mechanistic control, reactor engineering, product selectivity, and scale up readiness. Reported electrocatalysts include noble metals, transition metal oxides and hydroxides, metal phosphide derived oxyhydroxides, doped carbons, single atom catalysts, and molecular mediators, each contributing different advantages in activity, selectivity, and durability. The review also highlights the growing importance of microenvironment control, adsorption tuning, and in situ surface reconstruction in improving catalytic performance. Reactor development has advanced from batch H cells to continuous flow systems, membrane electrode assemblies, zero gap cells, and gas diffusion electrodes, enabling higher current densities, improved mass transfer, and better integration with downstream separations. Performance trends indicate that polyethylene terephthalate-derived feeds are currently the most tractable, with several systems achieving high Faradaic efficiencies and industrially relevant current densities under alkaline flow conditions. In contrast, the electroconversion of polyolefins remains less mature and often requires multistep or hybrid catalytic strategies. Despite encouraging progress, major barriers remain, including feedstock heterogeneity, catalyst degradation, salt management, separation energy, and inconsistent reporting standards. The review concludes that meaningful scale up will depend on standardized test feeds, harmonized performance metrics, integrated pilot demonstrations, co designed separation technologies, and policy support that can accelerate early markets for circular chemicals and fuels.