Improving the performance of photoelectrochemical CO reduction through ethylene glycol oxidation

Photoelectrochemical CO reduction (ECOR) is emerging as a sustainable alternative fuel production method to conventional methods and CO2 electrolysis. The reaction is most often coupled with oxygen evolution reaction (OER), which is energy-intensive and produces low-value product. To improve the system feasibility, we investigate replacing OER with ethylene glycol oxidation reaction (EGOR), which promises lower energy consumption, produces added-value glycolic acid and enables the recycling of waste PET. To achieve this, we compare CO electrolysis systems based on OER and EGOR. To achieve this, we propose and validate a simplified modelling framework. First, we give insight into the operation of the OER and EGOR based systems. When using modern EGOR catalyst, the voltage reduction exceeds 0.5 V, which translates into a 16% decrease in the reactor’s energy consumption at 400 mA cm−2. Next, we investigate the attractiveness of EGOR in solar-based systems in PV-EC, PEC and PV-PEC configurations. Due to the lower anodic potential, it enables the unbiased solar-based systems to operate at current densities exceeding 10 mA cm−2, marking a significant improvement versus OER based systems. The use of EGOR enabled an upcycling of PET-derived ethylene glycol at significant rate.