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 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.