The increase in CO2 emissions caused by skyrocketing demand for organic chemicals manufacturing emphasizes the need for a carbon-negative organic product synthesis mechanism to offset the increase. Nonthermal plasma CO2 conversion has emerged as a promising pathway to decarbonize chemicals synthesis, only requiring renewable energy, CO2, and water to enable turnkey and flexible generation of value-added chemicals at room temperature and pressure. We demonstrate that when a CO2 nonthermal plasma is discharged into a bicarbonate-containing electrolyte, high-energy free electrons are introduced into the water, which has been shown to facilitate the reduction of carbon dioxide in the solution, yielding chemical products such as oxalate, formate, and ethanol. The intermediate reduction reactions are thought to involve the generation of C- and O-containing radicals, but this has not been experimentally proven to date. This work aims to probe the radicals generated as a result of CO2 plasma-water interactions via electron paramagnetic resonance (EPR) spectroscopy. EPR confirms the formation of •CO2- and •CO3- radicals due to CO2 plasma-water interactions. Furthermore, we elucidate the contributions of CO2 plasma and aqueous carbonate species to the generation of C-containing radicals, providing further insight into the reaction mechanism leading to stable reduction products.
