Pivot roles of noble metal in single-phase TaXzON (0 < Z ≤ 0.001) and heterostructured Xδ/TaXz−δON (X = Pt, Ru, 0.001 < Z ≤ 0.016) visible light photocatalysts based on photoinduced interfacial charge transfer for hydrogen production

Abstract

Noble metal modification has been demonstrated to be an efficient strategy to improve the photocatalytic performance of TaON photocatalysts. However, the previous studies about the noble metal modification are only restricted to the surface loading of metallic noble metal, investigations have seldom been focused on the simultaneously deposited and doped X/TaX_zON (X = Pt, Ru) photocatalyst. In this work, single-phase Ta_1−zX_zO_1+zN_1−z (X = Pt, Ru, 0 < Z ≤ 0.001) (as TaX_zON) and heterostructured X_δ/Ta_1−z+δX_z−δO_1+z−δN_1−z+δ (X = Pt, Ru, 0.001 < Z ≤ 0.016) (as X_δ/TaX_z−δON) photocatalysts were synthesized by a sol–gel method in combination with a post-treatment nitridation process. The chemical states and form of noble metals in the as-prepared TaX_zON and X_δ/TaX_z−δON samples were characterized by XPS and HRTEM. In a few noble metal doping sol–gel processes, the visible-light photocatalytic activity of single-phase TaPt_zON (Z = 0.0005) and TaRu_zON (Z = 0.0005) showed a rate of H₂ production at 51 and 90 μmol h⁻¹ higher than that of the pristine TaON. With the increase of noble metal content, the photocatalytic activity of heterostructured Pt_δ/TaPt_z−δON (Z = 0.004) and Ru_δ/TaRu_z−δON (Z = 0.004) exhibited a rate of H₂ evolution at 198 and 258 μmol h⁻¹ which was about 28 and 6 times than the TaON loaded noble metal by photodeposition, respectively. Moreover, further photodeposition of noble metal was performed at the heterostructured materials. It was found that the highest photocatalytic activity of the catalyst was achieved based on X_δ/TaX_z−δON (X = Pt, Ru, Z = 0.002). This enhanced photocatalytic activity is mainly ascribed not only to the doping effect leading to formation of an isolated energy level contributing to more visible-light absorption but also to the well-distributed noble metal on the surface of the photocatalysts with strong interaction with TaON resulting in photoinduced interfacial charge transfer. This work may provide some insight into the smart design of novel and high-efficiency photocatalytic materials.