Sustainable Formate Synthesis: Integrating Ethylene Glycol Oxidation with Carbon Dioxide Electrocatalysis Using Redox-Stabilized Earth-Abundant Electrodes

Carbon dioxide electroreduction (CO2ER) coupled with water oxidation (oxygen evolution reaction, OER) presents a promising solution for effectively mitigating global warming. However, this process is compromised by the sluggish OER, which yields only undesirable O2. Here, we couple selective CO2ER with partial ethylene glycol oxidation (EGO) to concurrently produce formate in both half-reactions. The enhancement of active sites and optimization of formate selectivity are the principal objectives during the design of both electrodes. For CO2ER, redox stabilization of Sn-based cathodes is investigated via Pb doping, thus ultimately improving the Faradaic efficiency from 68% to ∼89%. To replace OER with EGO, we employed CuO@Ni(OH)2 on copper foam, reducing the applied potential by 200 mV at 50 mA/cm2. Finally, an EGO-coupled CO2 electrolyzer achieves 10 mA/cm2 at an overall cell voltage 180 mV lower than that of a conventional CO2 electrolyzer. This study showcases the integration of divergent electrochemical processes for concurrent electrosynthesis without precious metals to achieve cost-effective and sustainable formate production from CO2 and plastic waste.