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 (CO2 ) reduction technologies, where the reduction of CO2 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 CO2 . 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 CO2 to formate with a high Faradaic efficiency of 99±5 % at a mild applied potential of -0.66 V vs. SHE.