Electrolysis of ethylene-to-ethylene glycol paired with acidic CO2-to-CO

Abstract

Electrochemical conversion of CO2 into CO, ethylene, and other valuable chemicals is a promising method for carbon capture and utilisation. However, when carried out in an alkaline or neutral media, (bi)carbonate formation leads to low atom efficiency in the electrocatalytic process. In contrast, acidic conditions enable CO2 utilization >80%; but there is a need to lower full-cell voltage. In this work, we paired the acidic reaction cathodic CO2-to-CO with acidic anodic ethylene-to-ethylene glycol (C2H4-to-EG) for the first time. For the selective oxidation of ethylene to EG, we employed a homogeneous redox mediator ruthenium-polyoxometalate (Ru-POM) with gold-modified electrodes for the first time to facilitate the redox cycle. This resulted in enhanced selectivity and stability, achieving a Faradaic efficiency (FE) of 83% to EG. At the cathode, a porous nickel single-atom catalyst drives CO2-to-CO in an acidic electrolyte with a FE 97%. The paired system operates at a full-cell voltage of 3.1 V, compared to 3.3 V for a reference system using oxygen evolution reaction. The demonstrated system offers a promising route for reducing carbon emissions with high atom efficiency.