Study of photocatalytic activity in two light ranges of Sr$_2$Mn$_{0.4}$Ti$_{0.6}$O$_4$ oxide with the K$_2$NiF$_4$-type structure

The photocatalytic properties of single-phase sample Sr$_2$Mn$_{0.4}$Ti$_{0.6}$O$_4$ is studied as a representative of a series of Sr$_2$Mn$_x$Ti$_{1-x}$O$_4$ solid solutions ($x$ = 0.05, 0.15, 0.25, 0.4) obtained by the SHS. The sample annealed at 1200$^\circ$C is characterized by a uniform distribution of Sr, Ti and Mn in the oxidation degree (4+) inside the aggregates, the average size of which does not exceed 1$\mu$m. According to UV-Vis-NIR spectroscopy data, a narrowing of the band gap of Sr$_2$TiO$_4$ from 3.16 to 1.8 eV is observed when it is doped with 40 mol% of manganese. This is due to the high photoactivity of Sr$_2$Mn$_{0.4}$Ti$_{0.6}$O$_4$ in the HQ oxidation reaction in UV and blue light.