Tungsten Oxide-Based Z-Scheme for Visible Light-Driven Hydrogen Production from Water Splitting

Area of Science:

• Materials Science
• Photocatalysis
• Renewable Energy

Background:

• Solar-driven water splitting is crucial for renewable energy.
• Traditional Z-scheme systems require multiple photocatalyst types.
• Developing efficient and selective water-splitting systems is essential.

Purpose of the Study:

• To develop a novel Z-scheme system for visible-driven water splitting using only tungsten oxides.
• To achieve efficient and selective production of hydrogen (H2) and oxygen (O2).
• To investigate the mechanism of selective H2 and O2 evolution in neutral and alkaline solutions.

Main Methods:

• Fabrication of a Z-scheme system using sodium tungsten oxide bronze (Na0.56WO3-) and 2D tungsten trioxide (WO3) nanosheets.
• Visible-light-driven water splitting experiments in neutral and alkaline aqueous solutions.
• Analysis of H2 and O2 evolution rates, molar ratios, and apparent quantum yield.
• Density functional theory (DFT) calculations and experimental evidence to study adsorption mechanisms.

Main Results:

• The tungsten oxide-only Z-scheme system achieved efficient H2 (14 μmol h-1) and O2 (6.9 μmol h-1) production.
• An ideal H2:O2 molar ratio of 2:1 was obtained.
• A high apparent quantum yield of 6.06% at 420 nm under neutral conditions was recorded.
• Selective adsorption of iodide (I-) on Na0.56WO3- and iodate (IO3-) on WO3 was confirmed as the key mechanism.

Conclusions:

• A robust and efficient Z-scheme system for visible-driven water splitting was successfully constructed using only tungsten oxides.
• The system demonstrates selective H2 and O2 evolution, crucial for safe and practical applications.
• The preferential adsorption mechanism, supported by DFT calculations, explains the system's high selectivity.
• This approach offers a promising pathway for safe and efficient hydrogen and oxygen production via photocatalysis.