Abstract
The commercial P25 titania has been modified with transition metallic species (Cr, Co, Ni, and Cu), added by impregnation with aqueous solutions of the corresponding nitrates. The preparation procedure also includes a heat treatment (500 °C) in argon to decompose the nitrates, remove impurities and to strengthen the metal–TiO2 interaction. The catalysts have been thoroughly characterized using N2 adsorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-visible diffuse-reflectance spectroscopy (UV-vis DRS) and X-ray photoelectron spectroscopy (XPS), and have been tested in the aqueous phase decomposition of acetic acid and in the gas phase oxidation of propene, using an irradiation source of 365 nm in both cases. The photocatalytic activity of the four metal-containing catalysts varies with the nature of the metallic species and follows a similar trend in the two tested reactions. The effect of the nature of the added metallic species is mainly based on the electrochemical properties of the supported species, being Cu/P25 (the sample that contains copper) the best performing catalyst. In the photodecomposition of acetic acid, all the metal-containing samples are more active than bare P25, while in the gas phase oxidation of propene, bare P25 is more active. This has been explained considering that the rate-determining steps are different in gas and liquid media.
Highlights
With the increasing concern in the use of renewable resources and in finding better ways to use solar energy, solar light-activated photocatalysis has become an attractive tool
A series of M/TiO2 photocatalysts (M = Cr, Co, Ni, Cu) were prepared by impregnation of the commercial P25 titania followed by heat treatment in Ar at 500 ◦ C
The characterization results have shown that the textural properties of the M/P25-Ar photocatalysts are very close to those of bare P25-Ar, and only sample Cr/P25-Ar shows a slightly higher surface area
Summary
With the increasing concern in the use of renewable resources and in finding better ways to use solar energy, solar light-activated photocatalysis has become an attractive tool. Heterogeneous photocatalysis is a process of great potential for pollutants abatement in gas and liquid phases. This method has considerable advantages over some existing technologies: it destroys pollutants rather than transferring them to another phase; it usually leads to complete mineralization of organic pollutants into CO2 , H2 O and innocuous mineral salts; it operates at ambient conditions, with any type of substrate, without complex processing requirements and it can be implemented in both aqueous and gaseous applications [1,2]. Heterogeneous photocatalysis, a promising advanced oxidation technology for removing contaminants at trace levels [3], is selected to address the problem of two reactions of environmental interest: acetic acid decomposition and propene oxidation. Due to its high chemical stability and/or low biodegradability [5], HAc is a recalcitrant compound quite
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