Introducing Oxygen Vacancies into a WO₃ Photoanode through NaH₂PO₂ Treatment for Efficient Water Splitting

Area of Science:

• Materials Science
• Electrochemistry
• Photocatalysis

Background:

• Tungsten oxide (WO₃) is a promising photoanode material for photoelectrochemical (PEC) water splitting due to its high light absorption and suitable band structure.
• However, its application is limited by poor photoinduced electron-hole separation and subsequent recombination.

Purpose of the Study:

• To enhance the efficiency of WO₃ photoanodes for PEC water splitting.
• To suppress electron-hole recombination by introducing oxygen vacancies (O_V) on the WO₃ surface.

Main Methods:

• Surface modification of WO₃ photoanodes using sodium hypophosphite (NaH₂PO₂) treatment.
• Formation of an oxygen vacancy (O_V)-enriched amorphous surface layer (approx. 4 nm thick).
• Characterization of charge carrier density, electrochemical surface area, and charge transfer properties.

Main Results:

• NaH₂PO₂ treatment successfully introduced oxygen vacancies, creating an amorphous surface layer.
• The modified WO₃ photoanode exhibited increased charge carrier density and enlarged electrochemical surface area.
• Significant improvements in charge separation and surface injection efficiencies were observed.
• The charge transfer process was accelerated, leading to enhanced PEC performance.

Conclusions:

• Introducing oxygen vacancies via NaH₂PO₂ treatment is an effective strategy to mitigate electron-hole recombination in WO₃ photoanodes.
• The enhanced charge dynamics and surface properties contribute to improved photoelectrochemical water splitting performance.
• The modified WO₃ photoanode achieved a current density of 0.96 mA cm^-2 at 1.23 V, demonstrating its potential for efficient water splitting.