Photoelectrocatalytic plastic upcycling for biocatalytic CO₂ reduction

Photoelectrocatalytic upcycling of CO₂ and plastic wastes continues to be an effective approach to reducing the global carbon footprint and generating value-added fuels. However, simultaneous and selective conversion of these carbon wastes imposes high energy demands in the reforming process. Here, we report a sustainable and chemoselective waste-to-formate production platform that couples biocatalytic CO₂ fixation with photoelectrocatalytic polyethylene terephthalate (PET) plastic upcycling. In-situ spectroscopic analysis and density functional theory (DFT) calculations reveal that the Ni redox cycle (Ni²⁺→Ni^3+/4+) in a Ni(OH)₂-deposited hematite-based photoanode (i) selectively converts the hydrolyzed PET to formate and (ii) accelerates extraction of electrons from ethylene glycol (EG) in hydrolyzed PET. The PET-derived electrons on a carbon-based cathode activate a formate dehydrogenase via an ethyl viologen mediator, promoting chemoselective reduction of CO₂ into formate. The PET-fueled photobiocatalytic system achieved a millimolar-scale of formate production (161.2 mM) with a Faradaic efficiency (FE) of 172.2% over 96 h. This work demonstrates a concurrent valorization of CO₂ and plastic wastes in a biosolar platform for selective synthesis of formate and enhancement of integrated carbon management.