Enhanced photocatalytic ammonia oxidation activity and nitrogen selectivity over Ag/AgCl/N-TiO₂ photocatalyst

The removal of ammonia (NH₃) emitted from agricultural and industrial activities is of great significance to protect human health and ecological environment. Photocatalytic NH₃ oxidation to N₂ under mild conditions is a promising strategy. However, developing visible light photocatalysts for NH₃ oxidation is still in its infancy. Here, we fabricate N-TiO₂ and Ag/AgCl/N-TiO₂ photocatalysts by sol-gel and photodeposition methods, respectively. The introduction of N not only endows TiO₂ with visible light response (absorption edge at 460 nm) but also results in the formation of heterophase junction (anatase and rutile). Thus, N-TiO₂ shows 2.0 and 1.8 times higher than those over anatase TiO₂ and commercial TiO₂ for NH₃ oxidation under full spectrum irradiation. Meanwhile, surface modification of Ag can simultaneously enhance visible light absorption (generating localized surface plasmon resonance effect) and charge separation efficiency. Therefore, the photocatalytic activity of Ag/AgCl/N-TiO₂ is further improved. Furthermore, the presence of N and Ag also enhances the selectivity of N₂ product owing to the change of reaction pathway. This work simultaneously regulates photocatalytic conversion efficiency and product selectivity, providing some guidance for developing highly efficient photocatalysts for NH₃ elimination.