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

Rhodium-doped SrTiO3 perovskite as a monophasic titanate-based catalyst (SrTi1-xRhxO3) showed photocatalytic activity for oxygen evolution reaction (OER) from water under solar light irradiation with an instant induction period, although Rh4+ in SrTiO3 introduces deep trap states thereby diminishing the efficiency of the hydrogen evolution reaction (HER). Despite its potential, the exact crystal structure of Rh:SrTiO3 has not been yet completely investigated. Overcoming these challenges, here, we synthesized a monophasic SrTi0.95Rh0.05O3 (RSTO) perovskite oxide with a precisely determined crystal structure and highlighted an unconsidered pivotal role of the Rh iso-aliovalency reversibility that enables excellent photocatalytic water oxidation. With structural, morphological, optical, and electronic insights from XRD, FE-SEM, HR-TEM, XPS, and advanced XAS measurements in both total electron yield (TEY) and fluorescence yield (TFY), the oxygen evolution reaction (OER) process is attributed to the redox dynamics of Rh4+ ↔ Rh3+ synergistic interplay.