Sustainable Synthesis of Concentrated Formate via CO2 Electrolysis Integrated with Cl2 Formation

Integrating CO2 electrolysis with an industrially relevant anodic reaction enhances the economic feasibility and reduces carbon emissions in practical operations. In this study, we present an electrosynthesis strategy that integrates the CO2 reduction reaction to produce concentrated formate solution with the Cl2 formation in cation exchange membrane-based electrolyzers, scaling from 1 cm2 to 100 cm2 electrode areas. Our process, equipped with two automated pH regulation strategies, achieved selectivities over 80% for formate and 95% for chlorine in a 25 cm2 electrolyzer. Additionally, it demonstrated the ability to achieve formate concentrations up to 5.4 M during extended operation periods, establishing a new benchmark for electrochemical formate/formic acid synthesis. Techno-economic assessment and life cycle assessment further validated the process' sustainability, demonstrating a realistic path to profitability for valuable chemical production from CO2 even without considering potential subsidies and carbon taxes.