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

Abstract

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).