Monophasic Titanate-Based Photocatalyst with Heteroatom Mixed Iso-Aliovalency Enabling Water Oxidation

Area of Science:

• Materials Science
• Catalysis
• Photochemistry

Background:

• Rhodium-doped strontium titanate (SrTiO₃) perovskites show promise as photocatalysts for the oxygen evolution reaction (OER).
• The precise crystal structure and the exact mechanism of Rh-doped SrTiO₃ in photocatalysis remain incompletely understood.
• Deep trap states introduced by Rh⁴⁺ can hinder the hydrogen evolution reaction (HER).

Purpose of the Study:

• To synthesize and precisely determine the crystal structure of monophasic SrTi_0.95Rh_0.05O₃ (RSTO).
• To investigate the pivotal role of Rh iso-aliovalency reversibility in photocatalytic water oxidation.
• To elucidate the mechanism of the oxygen evolution reaction (OER) in RSTO.

Main Methods:

• Synthesis of monophasic SrTi_0.95Rh_0.05O₃ (RSTO).
• Structural, morphological, optical, and electronic characterization using XRD, FE-SEM, HR-TEM, XPS.
• Advanced X-ray absorption spectroscopy (XAS) measurements in total electron yield (TEY) and fluorescence yield (TFY) modes.

Main Results:

• A monophasic SrTi_0.95Rh_0.05O₃ perovskite oxide with a precisely determined crystal structure was successfully synthesized.
• The study highlights the critical role of reversible Rh⁴⁺ ↔ Rh³⁺ redox dynamics in enabling excellent photocatalytic water oxidation.
• Characterization confirmed the synergistic interplay of Rh⁴⁺ ↔ Rh³⁺ in the OER process.

Conclusions:

• The synthesized RSTO exhibits excellent photocatalytic activity for OER, driven by the reversible redox behavior of rhodium.
• Understanding the Rh iso-aliovalency reversibility is key to optimizing titanate-based photocatalysts for water splitting.
• This work provides crucial structural and mechanistic insights into Rh-doped SrTiO₃ for efficient photocatalytic water oxidation.