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

Rhodium-doped SrTiO 3 perovskite as a monophasic titanate-based catalyst (SrTi 1- x Rh x O 3 ) showed photocatalytic activity for oxygen evolution reaction (OER) from water under solar light irradiation with an instant induction period, although Rh 4+ in SrTiO 3 introduces deep trap states thereby diminishing the efficiency of the hydrogen evolution reaction (HER). Despite its potential, the exact crystal structure of Rh:SrTiO 3 has not been yet completely investigated. Overcoming these challenges, here, we synthesized a monophasic SrTi 0.95 Rh 0.05 O 3 (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 Rh 4+ ↔ Rh 3+ synergistic interplay.