NiO/Ni/TiO2 nanocables with Schottky/p-n heterojunctions and the improved photocatalytic performance in water splitting under visible light

Construction of Schottky junction or p-n heterojunction is admitted as an effective way for improving the separation of photo-induced carriers through its built-in electric field. In this work, fabrication of cooperative Schottky and p-n (SPN) heterojunction has been realized by intercalating metal Ni into a NiO/TiO2 p-n junction, forming a NiO/Ni/TiO2 Sandwich-like heterojunction. The special heterostructure was confirmed by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and the high-resolution transmission electron microscopic (HRTEM), Brunauer Emmett Teller (BET). After a serial of contrast experiments with solo Schottky or p-n junction, it was found that the electron-hole separation in this NiO/Ni/TiO2 SPN heterojunction was enhanced through charge transfer channel, and it was also in accordance with their related optical and photoelectrical properties characterizations, such as photoluminescence (PL) spectrum and UV-Vis diffused reflectance spectra. In the following photocatalytic water splitting process under visible light, the hydrogen generation rate of NiO/Ni/TiO2 reached up to 4653 mu mol h(-1) g(-1), which was 10.2, 6.7 and 2.3 times of those of TiO2 (457 mu mol h(-1) g(-1)), Ni/TiO2 (691 mot h(-1) g(-1)) with a Schottky junction and NiO/TiO2 (2059 mu mol h(-1) g(-1)) with a p-n junction, respectively. This SPN heterojunction with excellent photo-induced electron-hole separation ability opens a new window to exploring photocatalyst for water splitting. (C) 2018 Elsevier Inc. All rights reserved.