Upcycling CO2 and PET Waste: Ampere-Level Formate Electrosynthesis in an Integrated Electrolyzer.

The rising accumulation of poly(ethylene terephthalate) (PET) waste and atmospheric CO2 presents serious environmental and health challenges. Herein, we introduce a novel strategy for the simultaneous electrochemical upcycling of PET and CO2 in a single integrated electrolyzer, enabling ampere-level coproduction of formate. Leveraging careful electrode design of three-dimensional Ni foam at the anode for ethylene glycol (EG, derived from PET hydrolysis) electrolysis, formate formation at 1.2 A cm-2 was achieved─outperforming all reported performances for non-noble metal catalysts. A Bi2O2CO3-based gas diffusion electrode (GDE) enabled the selective reduction of CO2 (CO2RR) to formate at the cathode. By prioritizing enhanced reactant transport and electrode architecture beyond catalyst discovery, this integrated system achieved 100 h of stable operation at 0.50 A cm-2 with Faradaic efficiencies of 93.7% (anode) and 86.0% (cathode). Superior energy efficiency was achieved in the proposed membrane-free electrolyzer, with a cell voltage of 2.91 V at 1.0 A cm-2, reducing the input energy by 65% to ca. 0.1 kWh mol-1. This study highlights the critical role of anodic reaction choices and electrode engineering strategies in developing integrated electrolyzers with superior performance metrics.