(707a) Direct and Continuous Generation of Pure Liquid Fuels Via Electrocatalytic Carbon Dioxide Reduction

With continuously decreased price of renewable electricity, it becomes increasingly attractive to utilize electrical energy for the production of fundamental chemical feedstocks or fuels. Electrochemical CO₂ reduction reaction (CO₂RR) provides a green and sustainable “bottom-up” pathway to generate basic chemical feedstocks ranging from C₁ to C₃ products. Liquid fuels from CO₂RR, such as formic acid, methanol, acetic acid, ethanol, and propanol, are of particular interest due to their high energy densities and ease of storage and distribution. However, this route is still retarded by the following two long-standing challenges in the field: there is still a lack of highly selective, active, and stable catalysts for CO₂RR to produce target liquid fuels, especially for high-value products beyond formic acid; another challenge is that the liquid fuels generated from CO₂RR electrolysis are always in a mixture with conventional liquid electrolyte, which subsequently necessitates energy- and cost-intensive downstream separation processes to recover pure liquid fuels.

Through integrating rational designs in both catalyst and reactor, here we demonstrate a direct and continuous generation of high-purity and high-concentrated liquid fuels via electrochemical CO₂/CO reduction. By designing a novel porous solid electrolyte (PSE) layer between cathode and anode, other than traditional liquid electrolyte, efficient ionic transport was successfully maintained while no impurity ions (e.g. K⁺, Na⁺, HCO₃^-, OH^-...) were mixed into generated liquid fuel. When employed in this novel PSE reactor, we successfully demonstrated directly producing pure formic acid solutions from CO₂RR on Bi-based catalysts with nearly 100 % purity. Through flexible tuning of the carrier gas stream, we also achieved an ultra-high concentration up to nearly 100 wt.%.