Papers

Author: Long Ma (Chong Qing University) - CO₂ electrolysis offers an efficient pathway to produce carbon-based chemicals and fuels using renewable energy and resources. However, it remains a major challenge to accomplish both high current densities and long-term stable operation to satisfy industrial application demands. A prevalent strategy to overcome CO₂ transport limitation is the adoption of gaseous CO₂ feedstock electrolysis systems. The gaseous electrochemical reduction of CO₂ (ECR) system can employ hydrophobic gas diffusion electrode efficiently deliver CO₂ to active catalytic interfaces, achieving current densities exceeding 500 mA cm⁻² that satisfy industrial operational requirements. However, gaseous CO₂ can readily react with hydroxyl ions, which are produced during cathodic reduction, to form (bi)carbonates precipitates. Strategies such as physical washing, pulsed operation, and the use of bipolar membranes can partially alleviate these problems but do not fully resolve them. Aqueous-phase ECR is considered a promising route to inhibit carbonate formation during CO₂ electroreduction, thereby addressing the issues of carbonate crystallization. This system would eliminate the need for hydrophobic gas diffusion layers, in principle overcoming challenges associated with flooding and salt formation in conventional gas-phase ECR [1]. However, because the diffusion rate of CO₂ in water is approximately four orders of magnitude lower than in the gas-phase, CO₂ mass transport in aqueous-phase ECR system severely limited [2]. Herein, we propose a pressurized aqueous-based CO₂ electrolyzer, by enhancing CO₂ mass transport and achieving ampere-level ECR current densities. It is found that CO2 pressurization strategy not only promoted CO₂ mass transport, but also effectively improved the kinetics of ECR. Under the optimum conditions, aqueous-based CO₂ electrolyzer achieved over 95% CO Faraday efficiency at 1000 mA cm-2 under 6 atm of CO₂.