Enhanced photocatalytic degradation of VOCs using Ln³⁺-TiO₂catalysts for indoor air purification

Abstract

Two types of lanthanide ion-doped titanium dioxide (Ln³⁺–TiO₂) catalysts including La³⁺–TiO₂and Nd³⁺–TiO₂were prepared by a sol–gel method. The effects of the lanthanide ion doping on the crystal structure, surface area, adsorption properties, pore size distribution, and surface chemical state of the catalysts were investigated by means of XRD, BET,and XPS. As results,the crystal size decreased significantly, while the specific surface area, t-plot total surface area, micropore volume, and the total pore volume increased owing to the lanthanide ion doping. The nitrogen adsorption–desorption isotherms of the catalysts showed that the N₂adsorption ability of the Ln³⁺–TiO₂catalysts was better than the TiO₂catalyst. Among them, the 0.7% Ln³⁺–TiO₂catalysts demonstrated the highest adsorption ability. The photocatalytic activity of the catalysts was investigated in the experiments of the photocatalytic degradation of benzene,toluene,ethylbenzene and o-xylene (BTEX) in a gaseous phase. The photocatalytic efficiency of the TiO₂catalysts with the lanthanide ion doping was remarkably enhanced by BTEX removal. The 1.2% Ln³⁺–TiO₂catalysts achieved the highest photocatalytic activity. The enhanced photodegradation of BTEX is possibly due to the improved adsorption ability and the enhanced electron–hole pairs separation due to the presence of Ti³⁺ on the surface of Ln³⁺–TiO₂catalysts and the electron transfer between the conduction band/defect level and lanthanide crystal field state.