Boosting Current Density of Electrocatalytic CO ₂ Reduction using Metal–Enzyme Hybrid Cathodes

Abstract As a promising solution to global warming, electrocatalytic reduction of carbon dioxide (CO 2 RR) to liquid fuel has attracted great attention. A primary challenge in industrializing CO 2 RR technologies for producing liquid fuel is the mass transfer limitation of CO 2 , which significantly reduces the current density of CO 2 RR. This study proposes a new enzyme‐enhanced electrocatalysis platform for boosting CO 2 RR current density. This platform integrates an enzyme of bovine carbonic anhydrase (bCA), stabilized on carbon nanotubes (bCA@CNT), into formate/formic acid selective metal catalysts such as tin (Sn) and bismuth (Bi) to prepare Metal‐bCA (M‐bCA) hybrid cathodes. The incorporation of bCA enhances both the CO 2 hydration and the reversible dehydration of bicarbonate to CO 2 in the cathode. This dynamic catalysis of bCA facilitates rapid local regeneration of dissolved CO 2 from bicarbonate at the catalyst surface, thereby boosting the current density of CO 2 RR. Consequently, the formate current density of the Sn‐bCA cathode was 3.3 times higher than that of the bare Sn cathode in a membrane‐electrode assembly (MEA)‐type cell. Furthermore, the Bi‐bCA cathode achieved an excellent current density of 442 mA cm −2 , 1.5 times higher than the bare Bi cathode, for direct production of highly concentrated (3.4 mol L −1 ) formic acid in a 3‐compartment cell.