Surface acidity, catalytic and photocatalytic activities of new type H3PW12O40/Sn-TiO2 nanoparticles

TiO2 and Sn+4 doped TiO2 nanoparticles were prepared via the surfactant-assisted sol-gel method. Then, H3PW12O40 (PTA) was loaded over Sn-TiO2 nanoparticles with different PTA contents by wet impregnation method. The samples have been characterized by XRD, TEM, SEM, FTIR, UV-vis diffuse reflection (DRS) and photoluminescence spectroscopy (PL). The surface acidity was studied by potentiometric titration and the pyridine was used as probe molecules to distinguish between Bronsted and Lewis acid sites. XRD patterns analysis indicates that the crystallite size reduced remarkably with increasing PTA loading. TEM and SEM images exhibit irregular particles shape and the amount of PTA on the Sn-TiO2 surface increased with increasing PTA loading up to 60% wt. The addition of PTA and Sn+4 improved the surface acidity and catalytic activity of TiO2. Moreover, the addition of Sn+4 promoted the electrons transfer between PTA and TiO2 and reduced the recombination of electrons (e-) and holes (h(+)). The catalytic activity was tested by synthesis of 7-hydroxy-4methyl coumarin and 14-phenyl-14H-dibenzo [a,j] xanthene. Both the acidity and catalytic activity increased sharply after modification Sn-TiO2 by PTA and the sample with 50 wt% PTA showed the highest acidity and catalytic activity. Also, the photocatalytic performance of PTA/Sn-TiO2 was confirmed in the degradation of Methylene Blue (MB) and Rhodamine B (RhB) under UV-vis irradiations. The mineralization of MB and RhB were confirmed by Chemical oxygen demand (COD) and total organic carbon (TOC). The results indicate that 20% PTA/Sn-TiO2 showed the highest photocatalytic activity.