Enhanced photocatalytic ammonia oxidation over WO3@TiO2 heterostructures by constructing an interfacial electric field

Abstract

WO₃ nanorods and xWO₃@TiO₂ (WO₃/TiO₂ mass ratio (x) = 1-5) photocatalysts were synthesized using the hydrothermal and sol-gel methods, respectively. The photocatalytic activities of xWO₃@TiO₂ for NH₃ oxidation first increased and then decreased with a rise in TiO₂ content. Among them, the heterostructured 3WO₃@TiO₂ photocatalyst showed the highest NH₃ conversion (58 %) under the simulated sunlight irradiation, which was about two times higher than those of WO₃ and TiO₂. Furthermore, the smallest amounts of by-products (i.e., NO and NO₂) were produced over 3WO₃@TiO₂. The enhancement in photocatalytic performance (i.e., NH₃ conversion and N₂ selectivity) of 3WO₃@TiO₂ was mainly attributed to the formed interfacial electric field between WO₃ and TiO₂, which promoted efficient separation and transfer of photogenerated charge carriers. Based on the results of reactive species trapping and active radical detection, photocatalytic oxidation of NH₃ over 3WO₃@TiO₂ was governed by the photogenerated holes and superoxide radicals. This work combines two strategies of morphological regulation and interfacial electric field construction to simultaneously improve light utilization and photogenerated charge separation efficiency, which promotes the development of full-spectrum photocatalysts for the removal of ammonia.

Keywords: Core-shell structure; Interfacial electric field; Photocatalytic ammonia elimination; Titanium oxide; Tungsten oxide.