Probing the Site-Selective Doping in SrSnO₃:Eu Oxides and Its Impact on the Crystal and Electronic Structures Using Synchrotron Radiation and DFT Simulations

Abstract

The impact of Eu³⁺ doping at the Sr²⁺ and Sn⁴⁺ sites in SrSnO₃ on its structural and electronic properties was studied and correlated with the photocatalytic efficiency. The compounds were synthesized using a modified Pechini method. Refinement of the synchrotron X-ray diffraction (S-XRD) data showed that the samples had an orthorhombic <i>Pbnm</i> symmetry. The incorporation of Eu into the lattice led to increased short- and long-range disorder, inducing additional distortion in the SnO₆. XANES measurements revealed that mixed Eu valences (Eu³⁺ and Eu²⁺) were present in Eu-doped samples, and DFT calculations confirmed the presence of these ions at Sr²⁺/Sr⁴⁺ sites in the SrSnO₃, resulting in changes in the electronic behavior. The catalytic performance toward Remazol yellow dye photodegradation and the catalysts' surface properties were also evaluated. The catalytic efficiency followed the order of Sr(Sn_0.99Eu_0.01)SnO₃ > (Sr_0.99Eu_0.01)SnO₃ > SrSnO₃. The order was clearly related to selected-site doping that changed the degree of the inter- and intraoctahedral distortion and the introduction of different Eu midgap states, which apparently favor charge separation upon photoexcitation during photocatalysis. The results shown here are of great importance to the functionalization of SrSnO₃ and other perovskite materials by lanthanoid ions, especially Eu³⁺, for effective applications as photocatalysts.