Reactivation of standard [NiFe]-hydrogenase and bioelectrochemical catalysis of proton reduction and hydrogen oxidation in a mediated-electron-transfer system

Standard [NiFe]-hydrogenase from Desulfovibrio vulgaris Miyazaki F (DvMF-H(2)ase) catalyzes the uptake and production of hydrogen (H-2) and is a promising biocatalyst for future energy devices. However, DvMF-H(2)ase experiences oxidative inactivation under oxidative stress to generate Ni-A and Ni-B states. It takes a long time to reactivate the Ni-A state by chemical reduction, whereas the Ni-B state is quickly reactivated under reducing conditions. Oxidative inhibition limits the application of DvMF-H(2)ase in practical devices. In this research, we constructed a mediated-electron-transfer system by co-immobilizing DvMF-H(2)ase and a viologen redox polymer (VP) on electrodes. The system can avoid oxidative inactivation into the Ni-B state at high electrode potentials and rapidly reactivate the Ni-A state by electrochemical reduction of VP. H-2 oxidation and H+ reduction were realized by adjusting the pH from a thermodynamic viewpoint. Using carbon felt as a working-electrode material, high current densities-up to (200 +/- 70) and -(100 +/- 9) mA cm(-3) for the H-2-oxidation and H+-reduction reactions, respectively were attained. (C) 2018 Elsevier B.V. All rights reserved.