Proton Reduction Using a Hydrogenase-Modified Nanoporous Black Silicon Photoelectrode

Area of Science:

• Bioinorganic Chemistry
• Materials Science
• Renewable Energy

Background:

• Metalloenzymes with earth-abundant metals show catalytic activity for hydrogen evolution comparable to noble metals.
• Interfacing metalloenzymes with electrodes for efficient charge transfer in artificial systems is a significant challenge.

Purpose of the Study:

• To demonstrate a novel interface for binding metalloenzymes to an electrode surface.
• To evaluate the catalytic performance of a metalloenzyme-electrode system for hydrogen generation.

Main Methods:

• Fabrication of a nanoporous black silicon (b-Si) photocathode.
• Immobilization of [FeFe]-hydrogenase enzyme ([FeFe]-H2ase) onto the b-Si surface.
• Electrochemical characterization of the [FeFe]-H2ase/b-Si photoelectrode for hydrogen evolution.

Main Results:

• The [FeFe]-H2ase/b-Si photoelectrode exhibited a 280 mV more positive onset potential for hydrogen generation compared to bare b-Si.
• Achieved a turnover frequency of ≥1300 s⁻¹ and a turnover number >10⁷, sustaining current densities of ≥1 mA/cm².
• Performance was comparable to a b-Si/Pt electrode at similar light intensities.

Conclusions:

• Nanoporous black silicon provides an effective interface for immobilizing [FeFe]-hydrogenase, enabling high catalytic performance for hydrogen generation.
• This study extends the proof-of-concept for interfacing biologically derived metalloenzymes with inorganic substrates for technologically relevant current densities.
• Long-term stability of the enzyme on the b-Si surface requires further improvement for practical applications.