Bioelectrocatalytic CO2 Reduction by Redox Polymer-Wired Carbon Monoxide Dehydrogenase Gas Diffusion Electrodes

The development of electrodes for efficient CO2 reduction while forming valuable compounds is critical. The use of enzymes as catalysts provides the advantage of high catalytic activity in combination with highly selective transformations. We describe the electrical wiring of a carbon monoxide dehydrogenase II from Carboxydothermus hydrogenoformans (ChCODH II) using a cobaltocene-based low-potential redox polymer for the selective reduction of CO2 to CO over gas diffusion electrodes. High catalytic current densities of up to −5.5 mA cm−2 are achieved, exceeding the performance of previously reported bioelectrodes for CO2 reduction based on either carbon monoxide dehydrogenases or formate dehydrogenases. The proposed bioelectrode reveals considerable stability with a half-life of more than 20 h of continuous operation. Product quantification using gas chromatography confirmed the selective transformation of CO2 into CO without any parasitic co-reactions at the applied potentials.The authors are grateful for financial support from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) in the framework of the SPP2240 (e-biotech) [445820469] and the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska- Curie MSCA-ITN "ImplantSens" [813006]. J.A.B. acknowledges funding from the DFG SPP 1927 "Iron−Sulfur for Life" project (Project No. BI 2198/1-1) and the Max Planck Society. P.R.-M. thanks the University of Oxford for a Glasstone Research Fellowship and Linacre College Oxford for a Junior Research Fellowship