Self-supported copper-based gas diffusion electrodes improve the local CO2 concentration for efficient electrochemical CO2 reduction

Electrochemical CO₂ reduction is a sustainable approach in green chemistry that enables the production of valuable chemicals and fuels while mitigating the environmental impact associated with CO₂ emissions. Despite its several advantages, this technology suffers from an intrinsically low CO₂ solubility in aqueous solutions, resulting in a lower local CO₂ concentration near the electrode, which yields lower current densities and restricts product selectivity. Gas diffusion electrodes (GDEs), particularly those with tubular architectures, can solve these issues by increasing the local CO₂ concentration and triple-phase interface, providing abundant electroactive sites to achieve superior reaction rates. In this study, robust and self-supported Cu flow-through gas diffusion electrodes (FTGDEs) were synthesized for efficient formate production via electrochemical CO₂ reduction. They were further compared with traditional Cu electrodes, and it was found that higher local CO₂ concentration due to improved mass transfer, the abundant surface area available for the generation of the triple-phase interface, and the porous structure of Cu FTGDEs enabled high formate Faradaic efficiency (76%) and current density (265 mA¸cm⁻²) at–0.9 V vs. reversible hydrogen electrode (RHE) in 0.5 mol·L⁻¹ KHCO₃. The combined phase inversion and calcination process of the Cu FTGDEs helped maintain a stable operation for several hours. The catalytic performance of the Cu FTGDEs was further investigated in a non-gas diffusion configuration to demonstrate the impact of local gas concentration on the activity and performance of electrochemical CO₂ reduction. This study demonstrates the potential of flow-through gas-diffusion electrodes to enhance reaction kinetics for the highly efficient and selective reduction of CO₂, offering promising applications in sustainable electrochemical processes.