Efficient and cost-effective electrocatalysts for coproduction of formate through electrocatalytic oxidation of PET-derived ethylene glycol coupled with CO2 reduction

Electrocatalytic CO 2 reduction reaction (CRR) to produce value-added chemicals offers a sustainable strategy to address energy crisis and climate change. However, the conventional CRR is always coupled with the anodic oxygen evolution reaction (OER), suffering from large overpotential, and high energy consumption. To overcome this, we proposed an alternative system by pairing CRR with the electrocatalytic oxidation of ethylene glycol (EGOR), a product derived from the depolymerization of polyethylene terephthalate (PET) plastic waste. This novel coupled system enabled the simultaneous production of formate on both electrodes, achieving the dual utilization of plastic waste and CO 2 . In this study, we developed a commercially viable system combining a robust NiOOH electrocatalyst synthesized through a facile electrodeposition for EGOR with a low-cost Bi 2 O 3 electrocatalyst for CRR. The NiOOH electrocatalyst achieved Faradaic efficiencies over 88 % for EG oxidation into formate within a broad potential window (1.4–1.8 V RHE ), while Bi 2 O 3 delivered Faradaic efficiencies more than 90 % for CO 2 -to-formate conversion within −0.8 to −1.2 V RHE . When integrated in a two-electrode configuration, the EGOR/CRR system produced formate at both electrodes with Faradaic efficiencies above 85 % across a wide cell voltage (2.0–2.6 V), requiring a ∼300 mV lower cell potential compared to the OER/CRR system. This coupled system reached commercial-level current densities above 200 mA cm −2 or 400 mA cm −2 at 3.0 V when implemented in the flow cell or the MEA cell, respectively. These results demonstrated the potential to use waste-derived reactants and commercially accessible eletrocatalytsts to realize energy-efficient and scalable conversion into formate.