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 μmol h−1 g−1, which was 10.2, 6.7 and 2.3 times of those of TiO2 (457 μmol h−1 g−1), Ni/TiO2 (691 μmol h−1 g−1) with a Schottky junction and NiO/TiO2 (2059 μmol 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.