Effect of Manganese Concentration and Calcination Temperature on Photochemical Properties of TiOF2/MnO(OH)

The heterostructures TiOF2/(0.5–5 wt.%)MnO(OH) attract attention as potential catalysts for pollutant removal from water. In this paper, a novel synthesis route was proposed through the precipitation of MnO(OH) particles out of an alkaline solution on the TiOF2 particles. The formation of manganese oxyhydroxide was confirmed by X-ray diffraction analysis. The presence of manganese in proportions up to 1 wt.% recalculated to MnO(OH) did not affect the morphology of TiOF2/MnO(OH) particles. Higher concentrations of Mn caused the appearance of mostly spherical particles of dimensions ca. 100 nm. The effect of calcination temperatures 300–600 °C on the structure and photocatalytic activity of the particles was analyzed. It was found that calcination of the powder formed TiO2 phase with mainly anatase structure as well as Mn3O4. After calcination at 600 °C, the appearance of fluorine was detected, indicating the formation of fluorinated titanium dioxide. For higher manganese concentrations, the fluorine proportion in F-TiO2 samples decreased. Increased Mn content in TiOF2/MnO(OH) significantly improved its photocatalytic activity, shortening the degradation time and increasing the degradation degree of methylene blue (MB). However, an increase in the calcination temperature decreased the degradation degree of MB. It was found that the optimal concentration of MnO(OH) was 5 wt.%.