Interfacial Bi-S bonds modulate band alignment for efficient solar water oxidation.

Area of Science:

• Materials Science
• Photochemistry
• Catalysis

Background:

• Interfacial chemical bonds are crucial for enhancing photoanode performance in photoelectrochemical (PEC) water oxidation.
• Tuning these bonds and understanding their effect on band alignment and charge dynamics is challenging.

Purpose of the Study:

• To introduce Bi-S bonds at the CdIn2S4 (CIS)/Bi2WO6 (BWO) heterojunction interface.
• To investigate the influence of Bi-S bonds on band alignment and charge carrier dynamics.
• To optimize photoanode performance for PEC water oxidation.

Main Methods:

• Fabrication of CIS/BWO heterojunctions with introduced Bi-S bonds.
• In situ irradiated X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) for interfacial analysis.
• Theoretical calculations to understand charge transfer mechanisms.
• Photoelectrochemical measurements to evaluate performance.

Main Results:

• The introduction of Bi-S bonds successfully modified the band alignment from type II to a direct Z-scheme.
• Enhanced carrier separation efficiency was observed due to the Bi-S bond acting as an atomic-level charge transfer channel.
• The optimized CIS/BWO photoanode achieved a photocurrent density of 4.25 mA cm-2 at 1.23 V vs. RHE and a low onset potential of 0.30 V RHE.

Conclusions:

• Atomic-level tuning of interfacial structures, specifically through the introduction of Bi-S bonds, can significantly improve photoanode performance for PEC water oxidation.
• The direct Z-scheme band alignment facilitated by Bi-S bonds is key to enhanced charge separation and extraction.
• This study offers a novel strategy for designing advanced photoanodes by precise control of interfacial chemistry.