ИСТИНА

Further improvement of the photocatalytic activity (PCA) of titania based catalysts is one of the key research issues in the field of heterogeneous catalysis. Unfortunately, the presence of the “invisible” XRD-amorphous part in the catalysts is often underestimated. This decreases the validity of comparison between different catalysts, because the PCA of the amorphous phase is significantly lower than that of crystalline samples. Therefore, a reliable quantitative method for the amorphous phase analysis is required. In this study we quantitatively measured the total amorphous phase amount in commercially available P25 Evonik (Degussa) and Hombikat UV100 titania catalysts, as well as in pre-synthesized mesoporous titania by XRD phase analysis of multiple sample/standard mixtures. Furthermore, we could distinguish the water content in the amorphous phase from water adsorbed on the material surface using thermal analysis. Additionally, PCA measurements were performed in liquid in an IceGlass quartz reactor with the use of methyl orange (MO) as a photodegradable agent. A high-pressure Hg bulb (5W) was used for illumination. The pH stabilization was achieved using a phosphate buffer solution (pH 6.7). MO concentration changes were measured every 3-5 sec. in a U-shape flow cell with continuous sampling by a peristaltic pump system. We found the negative correlation between the weight amount of amorphous phase and the PCA of titania catalysts. This result was confirmed by measurements of the annealed samples with the decreased amount of the amorphous phase. This work was supported by RFBR (grant №15-03-99537 А) and M.V.Lomonosov Moscow State University Program of Development.