Highly efficient photo-oxidation of water-soluble and gaseous organic pollutants over ZnO:ZnWO4 heterostructure

Reference	Presenter	Authors (Institution)	Abstract
05-010	Kele Tatiane Gomes Carvalho	Carvalho, K.T.(Brazilian Agricultural Research Corporation); Lopes, O.F.(University of Sao Paulo); Ferreira, D.C.(University of Sao Paulo); Ribeiro, C.(Brazilian Agricultural Research Corporation, São Carlos, SP, Brazil);	The heterogeneous photocatalysis applied to organic contaminants degradation in liquid and gaseous phases has received increasing attention due to the simple operation, low cost, reusability, clean and safe. However, most of the widely used photocatalysts have two main limitations in practical applications: (i) the low solar energy conversion efficiency due to their wide band gap and (ii) the high recombination rate of photoinduced electron-hole pairs. In this sense, suitable heterostructures formation between different semiconductors has attracted attention due to the great potential to provide a viable alternative to improve their photocatalytic performances. Zinc oxide (ZnO) is an important n-type semiconductor with an energy band gap of 3.4 eV (wurtzite phase) that have been extensively investigated due to its remarkable photocatalytic properties. Among various materials with high potential to be designed as heterostructures with ZnO, zinc tungstate (ZnWO4) arises as an interesting material due to its proper physical and electronic properties. Thus, we report here a versatile ZnO:ZnWO4 heterostructure suitable for photocatalytic degradation of pollutants in liquid and gaseous media. The materials could be easily prepared by a hydrothermal method driven by the difference in chemical solubility of the components, enabling good morphological control and providing catalysts with high surface areas. This heterostructured material was effective in the oxidation of methylene blue dye, caffeine, and drug amiloride in aqueous solution, and ethylene gas under UV irradiation. The enhanced photocatalytic performance of the ZnO:ZnWO4 heterostructures compared to the isolated phases was attributed to the spontaneous formation of heterojunctions between ZnO and ZnWO4 during the synthesis step, increasing electron/hole pair lifetimes. In addition, recycling experiments revealed that the heterostructure was stable over time, indicating the commercial potential of this material.
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