Morphology-controlling hydrothermal synthesis of h-WO3 for photocatalytic degradation of 1,2,4-trichlorobenzene

The controlled preparation of hexagonal tungsten trioxide under hydrothermal conditions was developed by adjusting of pH value of the initial reaction solution. The effect of pH on the morphology, composition, texture and thermal stability of the as-prepared oxides was characterized via XRD, SEM, TEM, TG-DSC-MS, BET methods, FT-IR, Raman and UV–Vis spectroscopies. The results indicate that the h-WO3 nanobelts prepared at pH = 2.3 exhibit the highest photocatalytic performance in methanol medium for UV-excited degradation of the hardly destructible chlorarene - 1,2,4-trichlorobenzene (99.2 % in 100 h), while the commercial m-WO3 shows a lower performance, especially, at initial period of action. The origin of difference between prepared and commercial samples is understood using the DFT study of methanol radicalization at the surfaces of h-WO3 and m-WO3, unveiling a promoted formation of methoxy-radicals at the surface of h-WO3 in addition to conventional formation of hydroxymethyl-radicals.