Catalytic and photocatalytic performance of mesoporous CuxO–TiO2

In this work the synthesis of mesoporous CuxO–TiO2 xerogels and their application in the catalytic and photocatalytic degradation of azo dye acid black 1 (AB1) are presented. To study the effect of Cu precursor, copper (II) formate, copper (II) chloride, and copper (II) nitrate were incorporated into the titanium alkoxide solution at various Cu/Ti atomic ratios. XRD, TEM, and N2-adsorption studies evidenced the crystallite size and textural properties dependency on Cu-precursor and Cu/Ti ratio. All catalysts were mesoporous and underwent pore enlargement with increasing Cu content. They showed first order kinetics for AB1 discoloration with the reaction rate constant k being in the range of 0.2–0.5 min−1 in catalytic degradation (dark experiments), slightly improving under diffuse illumination, and clearly increasing under UV light in catalysts obtained from inorganic precursors with large Cu content. Under dark conditions, degradation proceeds through a Fenton like mechanism, while under illumination it benefits from interfacial charge transfer from TiO2 to Cu (II). Both mechanisms require an intimate contact between Cu (II) and titania, which is favored in catalysts formed from inorganic Cu-precursors, in contrast to formate precursors that favored bulk CuO formation.