Molecular Engineering of Poly(Ionic Liquid) for Direct and Continuous Production of Pure Formic Acid from Flue Gas

Electrochemical CO₂ reduction reaction (CO₂RR) offers a promising approach to close the carbon cycle and reduce reliance on fossil fuels. However, traditional decoupled CO₂RR processes involve energy-intensive CO₂ capture, conversion, and product separation, which increases operational costs. Here, we report the development of a bismuth-poly(ionic liquid) (Bi-PIL) hybrid catalyst that exhibits exceptional electrocatalytic performance for CO₂ conversion to formate. The Bi-PIL catalyst achieves over 90% Faradaic efficiency for formate over a wide potential range, even at low 15% v/v CO₂ concentrations typical of industrial flue gas. The biphenyl in PIL backbone affords hydrophobicity while maintaining high ionic conductivity, effectively mitigating the flooding issues. The PIL layer plays a crucial role as a CO₂ concentrator and co-catalyst that accelerates the CO₂RR kinetics. Furthermore, we demonstrate the potential of Bi-PIL catalysts in a solid-state electrolyte (SSE) electrolyzer for the continuous and direct production of pure formic acid solutions from flue gas. Techno-economic analysis suggests that this integrated process can produce formic acid at a significantly reduced cost compared to the traditional decoupled approaches. This work presents a promising strategy to overcome the challenges associated with low-concentration CO₂ utilization and streamline the production of valuable liquid fuels and chemicals from CO₂.