Comparison of photocatalytic activity of αFe2O3-TiO2/P on the removal of pollutants on liquid and gaseous phase

The photocatalytic activity of mixed oxide α-Fe2O3/TiO2 doped with P (αFe-Ti/P) was evaluated on diuron degradation in aqueous solution and NOx oxidation under UV and visible light irradiation. The microwave-assisted sol-gel route was used to prepare the αFe-Ti/P catalyst. The TiO2 doped with P (Ti/P), α-Fe2O3/TiO2 (αFe-Ti) and TiO2 (Ti) were also synthesized under similar conditions as reference catalysts. The samples were characterized by different instrumental techniques (XRD, UV–VIS with DRS, PL, N2 adsorption, pHPZC, XPS, HRTEM, and FTIR). The photocatalytic activity on diuron degradation in aqueous media under UV and visible light followed the tendency Ti/P > αFe-Ti/P > αFe-Ti > Ti. The characteristics of the catalysts that enhanced photocatalytic reaction in liquid media were the low value of point of zero charge associated with Brønsted surface acid sites, narrow band-gap, small crystallite size, reduced e-/h+ recombination rate, and large surface area attributed to the P incorporation on the TiO2. On the other hand, the NOx oxidation on the gas-phase reaction under UV and visible light followed the trend αFe-Ti > Ti > Ti/P > αFe-Ti/P. These results could be related to the assemble of αFe2O3 nanoparticles with TiO2 to form αFe2O3/TiO2 heterostructure that extended the optical absorption in the visible range and increased the basicity of the prepared TiO2 based material (Lewis basic surface sites).