Transparent Ta₃ N₅ Photoanodes for Efficient Oxygen Evolution toward the Development of Tandem Cells

Area of Science:

• Materials Science
• Electrochemistry
• Renewable Energy

Background:

• Photoelectrochemical water splitting is a key technology for sustainable hydrogen production.
• Developing efficient photoelectrodes is crucial for practical water splitting systems.

Purpose of the Study:

• To fabricate transparent tantalum nitride (Ta3N5) photoanodes on GaN/sapphire substrates.
• To construct a tandem cell for overall water splitting and hydrogen evolution.

Main Methods:

• Fabrication of transparent Ta3N5 photoanodes on n-type GaN/sapphire.
• Integration of Ta3N5 with a photocathode for tandem water splitting.
• Construction of a stand-alone tandem cell using a dual-CuInSe2 (CIS) unit and Pt/Ni electrode.

Main Results:

• Achieved a photocurrent of 6.3 mA/cm² at 1.23 V vs. RHE with the GaN-interlayered Ta3N5 photoanode.
• Ta3N5 transparency (>600 nm) enabled light transmission to the CIS photocathode (absorbs up to 1100 nm).
• Demonstrated a solar-to-hydrogen conversion efficiency exceeding 7% in the tandem cell.

Conclusions:

• Transparent Ta3N5 photoanodes are effective for promoting O2 evolution in tandem water splitting.
• The developed tandem cell architecture shows significant potential for efficient hydrogen generation.
• This approach advances the development of practical photoelectrochemical systems for renewable hydrogen production.