Electrochemical properties of hydrogenase on glass carbon electrodes modified with carbon nanotubes

Abstract

Hydrogenase (H2 ase) purified from phototropic bacteriumThiocapsa roseopersicina was coassembled with carbon nanotubes (CNTs) on glass carbon electrodes. Both oxidized CNTs and Nafion-CNT composites were used to modify the electrodes. The pure H2 are formed dot-like domains, while the oxidized CNT-H2 ase and Nafion-CNT-H2 ase composites formed wire-like and large closely packed aggregates, respectively. The reductive potentials for the [4Fe-4S]2+/1+ clusters of H2ase were at about −500, −650, and −700 mV (vs Ag/AgCl) for the electrodes modified with pure H2ase, Nafion-SWNT-H2ase, and Nafion-MWNT-H2ase composites, respectively. Potential step chronocoulometry measurements indicated a larger charge-transfer diffusion coefficient between the H2ase and electrodes when the CNTs were co-assembled with H2ase, suggesting that the CNTs can not only act as a supporting layer to immobilize enzymes, but also act as a highly conductive wire throughout the films.