Nanostructured Ti-M mixed-metal oxides:Toward a visible light-driven photocatalyst

摘要

In this report we investigate the structure-activity relationship in Ti-M (M = V,Mo,Nb,W) mixed-metal oxides with anatase structure used for the photoelimination of toluene under sunlight-type excitation.These systems were prepared by a microemulsion method,and their physicochemical properties were characterized by a multitechnique approach using X-ray diffraction-Rietveld,photoelectron spectroscopy,and Raman and UV-visible spectroscopy.The preparation method allowed the incorporation of up to around 20 at% of Mo,Nb,and W,whereas a significantly inferior solubility limit,below 5 at% was observed for V.The presence of nonpunctual defects,intimately related to the existence of MO_x clustering,produced electronic mid-gap states involved in charge recombination and appeared to be the most negative factor influencing photoactivity.The maximization of photoactivity occurred for Ti-M samples with the highest doing level,together with a minimum structural disturbance of the anatase-type structure.The physicochemical bases for the photoactivity behavior of the Ti-M samples as function of the M content and,in particular,the presence of partial (for a specific Ti-M series) or global maxima are discussed.