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. Electroenzymatic CO2 reduction: A low‐potential redox polymer that contains cobaltocene grafted to poly(allylamine) was designed to simultaneously mediate electron transfer to the molybdenum‐dependent formate dehydrogenase (Mo‐FDH) from Escherichia coli (a metalloenzyme that interconverts formate and CO2) and immobilize Mo‐FDH at the surface of a carbon electrode. The resulting bioelectrode reduces CO2 to formate with high Faradaic efficiency.