Creating a Low‐Potential Redox Polymer for Efficient Electroenzymatic CO₂ Reduction

Increasing greenhouse gas emissions have resulted in greater motivation to find novel carbon dioxide (CO 2 ) reduction technologies, where the reduction of CO 2 to valuable chemical commodities is desirable. Molybdenum‐dependent formate dehydrogenase (Mo‐FDH) from Escherichia coli is a metalloenzyme that is able to interconvert formate and CO 2 . We describe a low‐potential redox polymer, synthesized by a facile method, that contains cobaltocene (grafted to poly(allylamine), Cc‐PAA) to simultaneously mediate electrons to Mo‐FDH and immobilize Mo‐FDH at the surface of a carbon electrode. The resulting bioelectrode reduces CO 2 to formate with a high Faradaic efficiency of 99±5 % at a mild applied potential of −0.66 V vs. SHE.