Enhanced Charge Carrier Separation in WO₃/BiVO₄ Photoanodes Achieved via Light Absorption in the BiVO₄ Layer

Area of Science:

• Materials Science
• Photochemistry
• Renewable Energy

Background:

• Photoelectrochemical (PEC) water splitting converts solar energy and water into hydrogen and oxygen.
• Tungsten trioxide (WO3) and bismuth vanadate (BiVO4) heterojunctions show improved PEC performance over individual components.
• Internal charge recombination limits PEC efficiency in WO3/BiVO4 systems when both materials absorb light.

Purpose of the Study:

• To enhance photoelectrochemical water splitting efficiency by optimizing WO3/BiVO4 heterojunction performance.
• To investigate the role of the BiVO4 layer in sensitizing WO3 and preventing direct photoexcitation.
• To improve charge separation and reduce recombination losses in WO3/BiVO4 photoanodes.

Main Methods:

• Fabrication of WO3/BiVO4 heterojunction photoanodes with varying BiVO4 layer thicknesses.
• Photoelectrochemical (PEC) measurements under frontside (through BiVO4) and backside (through WO3) irradiation.
• Ultrafast transient absorption spectroscopy to analyze charge carrier dynamics.

Main Results:

• Frontside irradiation through the BiVO4 layer significantly enhanced charge separation compared to backside irradiation.
• Optimized WO3/BiVO4 electrodes demonstrated a 40% increase in photocurrent density under frontside irradiation.
• Spectroscopic analysis confirmed improved charge dynamics and reduced recombination with the BiVO4 sensitization strategy.

Conclusions:

• Exploiting the BiVO4 layer to sensitize WO3 and shield it from direct photoexcitation is an effective strategy to boost PEC water splitting.
• Optimized light management in WO3/BiVO4 heterojunctions is crucial for maximizing solar hydrogen production.
• This approach offers a pathway to more efficient and cost-effective solar fuel generation.