Bioelectrocatalytic formate oxidation and carbon dioxide reduction at high current density and low overpotential with tungsten-containing formate dehydrogenase and mediators.

We show a great possibility of mediated enzymatic bioelectrocatalysis in the formate oxidation and the carbon dioxide (CO 2 ) reduction at high current densities and low overpotentials. Tungsten-containing formate dehydrogenase (FoDH1) from Methylobacterium extorquens AM1 was used as a catalyst and immobilized on a Ketjen Black-modified electrode. For the formate oxidation, a high limiting current density ( j lim ) of ca. 24 mA cm − 2 was realized with a half wave potential ( E 1/2 ) of only 0.12 V more positive than the formal potential of the formate/CO 2 couple ( E °′ CO2 ) at 30 °C in the presence of methyl viologen (MV 2 + ) as a mediator, and j lim reached ca. 145 mA cm − 2 at 60 °C. Even when a viologen-functionalized polymer was co-immobilized with FoDH1 on the porous electrode, j lim of ca. 30 mA cm − 2 was attained at 60 °C with E 1/2 = E °′ CO2 + 0.13 V. On the other hand, the CO 2 reduction was also realized with j lim ≈ 15 mA cm − 2 and E 1/2 = E °′ CO2 − 0.04 V at pH 6.6 and 60 °C in the presence of MV 2 + . [ABSTRACT FROM AUTHOR]