Perovskite-like LaxSr2−xTi1−x/2Cux/2O4 (x = 0.2, 0.3, 0.5) oxides with the K2NiF4-type structure active in visible light range: new members of the photocatalyst family

A layered perovskite-like oxides LaxSr2−xTi1−x/2Cux/2O4 (x = 0.2, 0.3, 0.5) with a K2NiF4-type structure were obtained. The introduction of copper into the titanium sublattice reduces the band gap. Copper in these materials serve as a photoactivity regulator and is presented in two oxidation states in accordance with optical, voltammetric and EPR data. LaxSr2−xTi1−x/2Cux/2O4 (x = 0.2) exhibits the greatest photoactivity in the oxidation of phenolic compounds and As(III) under the influence of UV and blue light; with increasing degree of substitution x, the photoactivity of LaxSr2−xTi1−x/2Cux/2O4 decreases. This is explained by the formation of a magnetic polaron, which is observed in LaxSr2−xTi1−x/2Cux/2O4 (x = 0.5) in the temperature range from 50 to 200 K and is proven by ESR method. The expansion of the spectral range of LaxSr2−xTi1−x/2Cux/2O4 to the visible region is explained by the formation of acceptor levels $$\left( {{\text{Cu}}^{2 + } + {\text{e}}^{ - } \to {\text{Cu}}^{ + } / {\text{Cu}}^{ + } + {\text{h}}^{ + } \to {\text{Cu}}^{2 + } } \right)$$ in the band gap of Sr2TiO4, which increases the efficiency of separation of photogenerated electron–hole pairs. The presence of Cu (I) в LaxSr2−xTi1−x/2Cux/2O4 enhance photoactivity through the formation of active superoxygen radical on its surface ( $${\text{Cu}}^{ + } {\text{ + O}}_{{{2}\left( {{\text{ad}}} \right)}} \to {\text{Cu}}^{{2 + }} +\cdot{{\text{O}}}_{{2}}^{ - }$$ ).