Site‐Selected Doping of Upconversion Luminescent Er3+ into SrTiO3 for Visible‐Light‐Driven Photocatalytic H2 or O2 Evolution

A series of upconversion luminescent erbium‐doped SrTiO₃ (ABO₃‐type) photocatalysts with different initial molar ratios of Sr/Ti have been prepared by a facile polymerized complex method. Er³⁺ ions, which were gradually transferred from the A to the B site with increasing Sr/Ti, enabled the absorption of visible light and the generation of high‐energy excited states populated by upconversion processes. The local internal fields arising from the dipole moments of the distorted BO₆ octahedra promoted energy transfer from the high‐energy excited states of Er³⁺ with B‐site occupancy to the host SrTiO₃ and thus enhanced the band‐to‐band transition of the host SrTiO₃. Consequently, the erbium‐doped SrTiO₃ species with B‐site occupancy showed higher photocatalytic activity than those with A‐site occupancy for visible‐light‐driven H₂ or O₂ evolution in the presence of the corresponding sacrificial reagents. The results generally suggest that the introduction of upconversion luminescent agents into host semiconductors is a promising approach to simultaneously harnessing low‐energy photons and maintaining redox ability for photocatalytic H₂ and O₂ evolution and that the site occupancy of doped elements in ABO₃‐type perovskite oxides greatly determines the photocatalytic activity.