A robust ALD-protected silicon-based hybrid photoelectrode for hydrogen evolution under aqueous conditions

Area of Science:

• Materials Science
• Electrochemistry
• Renewable Energy

Background:

• Photo-electrochemical cells (PECs) offer a sustainable route for hydrogen production via water splitting.
• Key challenges for PECs include achieving sustainability, cost-effectiveness, and long-term stability.
• Developing efficient photocathodes from Earth-abundant elements is crucial for practical applications.

Purpose of the Study:

• To develop an efficient and stable photocathode platform for hydrogen evolution.
• To utilize Earth-abundant materials for cost-effective solar energy conversion.
• To investigate the performance of a novel catalyst-electrode assembly in PECs.

Main Methods:

• Fabrication of a photocathode using a p-type silicon substrate protected by atomic layer deposition (ALD) of TiO2.
• Coating with mesoporous TiO2 and covalent grafting of a cobalt diimine-dioxime molecular catalyst via phosphonate anchors.
• Application of a final ALD-TiO2 layer for enhanced stability.

Main Results:

• The developed photocathode efficiently catalyzes water reduction to hydrogen (H2) in a phosphate buffer (pH 7).
• An onset potential of +0.47 V vs. RHE was achieved, indicating favorable electrochemical performance.
• A current density of -1.3 ± 0.1 mA cm-2 at 0 V vs. RHE under AM 1.5 solar irradiation was recorded.
• The catalyst demonstrated a turnover number of 260 per hour and a turnover frequency of 0.071 s-1.

Conclusions:

• The reported photocathode platform demonstrates high efficiency and stability for solar-driven hydrogen production.
• The use of Earth-abundant materials and robust catalyst anchoring contributes to a cost-effective and sustainable energy solution.
• This work represents a significant advancement in the development of practical photo-electrochemical cells for renewable hydrogen generation.