Synthesis of n-type TaON microspheres decorated by p-type Ag₂O with enhanced visible light photocatalytic activity

Constructing p–n heterojunction photocatalysts with high performance has attracted great attention. Here, we report a microspherical Ag₂O/TaON p–n heterojunction as a novel and efficient visible-light-driven (VLD) photocatalyst. Porous TaON microspheres (diameters: 0.8–2 μm) were prepared by a solvothermal precipitation-nitridation method, and then the in situ growth of Ag₂O nanoparticles (size: ∼12 nm) on their surfaces was realized by a simple deposition method. All Ag₂O/TaON heterojunctions were much more active than pristine TaON or a mechanical mixture of Ag₂O and TaON in the degradation of organic pollutants (cationic dye rhodamine B, anionic dye methyl orange and neutral para-chlorophenol) under visible light (λ > 400 nm). Significantly, the highest photocatalytic activity was observed in the heterojunction with a Ag/Ta molar ratio of 0.1/1 (0.1Ag–Ta). The RhB degradation rate constant using 0.1Ag–Ta is approximately 9.7 and 3.1 times higher than those obtained by using TaON microspheres, and the mechanical mixture, respectively. The superior photocatalytic performance of Ag₂O/TaON is ascribed to the hierarchical superstructure and efficient charge separation. The mainly involved active species (holes and superoxide radicals) were identified via radical trapping experiments and electron paramagnetic resonance spectroscopy. The results demonstrate that Ag₂O/TaON is a potential VLD photocatalyst for wastewater treatment.