Solvated Electrons-Induced CO2 Valorization via Plasma–Liquid Interface for Sustainable Organic Acid Production

The escalating climate crisis driven by CO2 emissions necessitates performance- and energy-efficient carbon utilization technologies. Catalytic CO2 reduction and valorization into value-added organic acids hold significant promise, yet current systems often require precious metal catalysts, high temperatures, or elevated pressures. Herein, we demonstrate a catalyst-free plasma-electrochemical process for the one-step organic acid synthesis from CO2 and H2O under ambient conditions. This approach employs a gaseous plasma electrode powered by a negative DC source, coupling plasma excitation in the gas phase with solvated electron-induced CO2 reduction in the liquid. Through systematic optimization of key parameters, including electrolyte conductivity, alkali metal cation type, pH, temperature, and discharge configuration, the process achieves an oxalic acid formation rate of 71.68 μmol/h. Mechanistic studies, including product profiling and radical scavenging experiments, reveal that oxalic acid formation proceeds predominantly via solvated electron-mediated CO2 coupling through ·CO2– intermediates, while formic acid is generated from ·CO2– and ·CO hydrogenation. We expect that this work could establish a sustainable route for ambient-condition CO2 conversion using plasma-enabled electrochemistry, advancing the field of catalyst-free carbon valorization.