Perovskite-like La_xSr_2-xTi_1-x/2Cu< sub>x/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 La(x)Sr(2-x)Ti(1-x/2)Cu(x/2)O(4)to the visible region is explained by the formation of acceptor levels (Cu2++e(-)-> Cu+/Cu++h+-> Cu2+) in the band gap of Sr2TiO4, which increases the efficiency of separation of photo generated electron-hole pairs. The presence of Cu (I) & vcy; LaxSr2-xTi1-x/2Cux/2O4 enhance photoactivity through the formation of active superoxygen radical on its surface ( Cu++O-2(ad)-> Cu2++& sdot;O(-)2)