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

Abstract

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 Reversible Electrochemical Interconversion of Formate and CO2 by Formate Dehydrogenase from Cupriavidus necator

“…Several metal-based (iron, ruthenium, manganese, silver, palladium, and copper) catalysts have been employed in the literature to reduce CO 2 using electrochemical methods. , However, many of these systems are nonspecific (giving multiple products) and require high overpotentials, organic solvents, and high temperatures and pressures, which limits their practical applicability. Enzyme-based catalysis offers high specificity and function under ambient conditions and in neutral aqueous solution. − So far, only two enzyme classes are known to be capable of reducing CO 2 , Ni-dependent CO dehydrogenase (CO 2 → CO) and formate dehydrogenases isolated from different organisms (CO 2 → HCOO – ) …”

“…Enzymebased catalysis offers high specificity and function under ambient conditions and in neutral aqueous solution. 49−51 So far, only two enzyme classes are known to be capable of reducing CO 2 , Ni-dependent CO dehydrogenase (CO 2 → CO) 52 and formate dehydrogenases isolated from different organisms (CO 2 → HCOO − ). 51 C. necator FdsDABG is in fact one such enzyme and is highly efficient in the catalytic reduction of CO 2 to HCOO − (k cat = 11 s −1 ) with NADH as the chemical reductant.…”

Connecting Biological and Synthetic Approaches for Electrocatalytic CO2 Reduction

“…[149] The use of enzymes in CO 2 R electrolyzers is also emerging (Table 1). [49,58,154,155] For instance, a FDH from Methylbacterium extorquens, which required an electron mediator, was immobilized on PTFE-coated Ketjen Black and electroreduced CO 2 to formate at a low overpotential (when considering only the cathode potential) for 5 h. [154] While this biohybrid system achieved a record current density (À 18 mA cm À 2 ) using a high enzyme loading (1.2 nmol) on the GDE, the turnover frequency was comparable with solution-phase enzyme systems ( � 170 s À 1 for a GDE [154] versus � 50 s À 1 for solution phase [101] ). An alternative approach to immobilize FDH to GDEs is the use of redox polymers containing methyl viologen moieties.…”

Electrochemical energy storage in an organic supercapacitor via a non-electrochemical proton charge assembly

“…Amidst the pressing need to address escalating global energy demands and rapid industrialization, a great deal of attention has been focused on developing high-power and high-energydensity energy storage and conversion devices. [1][2][3][4][5][6][7] Electrochemical capacitors (ECs), or supercapacitors, have emerged as particularly promising candidates due to their superior power density, long lifetime, and high cyclic stability in comparison to secondary batteries. [8][9][10][11] These ECs can bridge the power-energy trade-off between batteries (high energy) and traditional dielectric capacitors (high power).…”