Visible Light-Driven Z-Scheme Water Splitting Using Oxysulfide H₂ Evolution Photocatalysts

Area of Science:

• Materials Science
• Photocatalysis
• Renewable Energy

Background:

• Developing efficient photocatalysts is crucial for sustainable energy solutions.
• Oxysulfide materials offer promising properties for visible-light-driven water splitting.
• Optimizing synthesis methods and cocatalyst loading is key to enhancing photocatalytic activity.

Purpose of the Study:

• To synthesize a Sm₂Ti₂S₂O₅ (STSO) oxysulfide photocatalyst with improved crystallinity and activity using a novel flux method.
• To investigate the effect of cocatalyst loading (IrO₂ and Pt) on the photocatalytic performance of STSO.
• To demonstrate a visible-light-driven Z-scheme water splitting system for H₂ and O₂ production using STSO and other oxysulfide photocatalysts.

Main Methods:

• Novel flux method for STSO synthesis.
• Co-loading of IrO₂ (oxidative) and Pt (reductive) cocatalysts onto STSO.
• Construction of a Z-scheme system using STSO for H₂ evolution and modified WO₃/PtO_x for O₂ evolution, with a triiodide/iodide redox mediator.

Main Results:

• The flux-method-synthesized STSO exhibited higher crystallinity and photocatalytic activity compared to conventionally prepared samples.
• Co-loading of both IrO₂ and Pt was essential for maximizing STSO's photocatalytic efficiency.
• Successful demonstration of visible-light-driven Z-scheme water splitting, producing H₂ and O₂.
• Other oxysulfide materials like La₅Ti₂CuS₅O₇ and La₆Ti₂S₈O₅ were also effective in the Z-scheme system.

Conclusions:

• The novel flux method is effective for preparing highly crystalline and active STSO photocatalysts.
• Cocatalyst selection and loading are critical for optimizing Z-scheme photocatalytic water splitting.
• The developed Z-scheme system provides a viable pathway for efficient solar-driven hydrogen production using various oxysulfide photocatalysts.