Site‐Selected Doping of Upconversion Luminescent Er 3+ into SrTiO 3 for Visible‐Light‐Driven Photocatalytic H 2 or O 2 Evolution

A series of upconversion luminescent erbium‐doped SrTiO 3 (ABO 3 ‐type) photocatalysts with different initial molar ratios of Sr/Ti have been prepared by a facile polymerized complex method. Er 3+ 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 BO 6 octahedra promoted energy transfer from the high‐energy excited states of Er 3+ with B‐site occupancy to the host SrTiO 3 and thus enhanced the band‐to‐band transition of the host SrTiO 3 . Consequently, the erbium‐doped SrTiO 3 species with B‐site occupancy showed higher photocatalytic activity than those with A‐site occupancy for visible‐light‐driven H 2 or O 2 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 H 2 and O 2 evolution and that the site occupancy of doped elements in ABO 3 ‐type perovskite oxides greatly determines the photocatalytic activity.