Hydrogen bioelectrooxidation on gold nanoparticle-based electrodes modified by Aquifex aeolicus hydrogenase: Application to hydrogen/oxygen enzymatic biofuel cells

• 20.0 ± 5.3 and 37.2 ± 4.3 nm gold nanoparticles were deposited on a gold electrode.
• O2- and CO-tolerant [NiFe] hydrogenase was immobilized on the AuNP deposits.
• Direct H2 oxidation was obtained with current densities up to 1.85 ± 0.15 mA·cm− 2.
• A biofuel cell was designed delivering 0.25 mW·cm− 2.

For the first time, gold nanoparticle-based electrodes have been used as platforms for efficient immobilization of the [NiFe] hydrogenase from the hyperthermophilic bacterium Aquifex aeolicus. AuNPs were characterized by electronic microscopy, dynamic light scattering and UV–Vis spectroscopy. Two sizes around 20.0 ± 5.3 nm and 37.2 ± 4.3 nm nm were synthesized. After thiol-based functionalization, the AuNPs were proved to allow direct H2 oxidation over a large range of temperatures. A high current density up to 1.85 ± 0.15 mA·cm− 2 was reached at the smallest AuNPs, which is 170 times higher than the one recorded at the bare gold electrode. The catalytic current was especially studied as a function of the AuNP size and amount, and procedure for deposition. A synergetic effect between the AuNP porous deposit and the increase surface area was shown. Compared to previously used nanomaterials such as carbon nanofibers, the covalent grafting of the enzyme on the thiol-modified gold nanoparticles was shown to enhance the stability of the hydrogenase. This bioanode was finally coupled to a biocathode where BOD from Myrothecium verrucaria was immobilized on AuNP-based film. The performance of the so-mounted H2/O2 biofuel cell was evaluated, and a power density of 0.25 mW·cm− 2 was recorded.