Ultrathin metal Ni layer on ZnO/TiO2 photoelectrodes with excellent photoeletrochemical performance in multiple electrolyte solutions

It is well known that the oxygen vacancy (Ovac) as the electron-donor dopant in semiconductor can increase the electron-holes separation in photoeletrochemical (PEC) water splitting. Furthermore, the metal Ni can promote the hydrogen evolution reaction (HER) on the surface of semiconductor. In this paper, the ZnO/TiO2 photoelectrodes with rich Ovac was synthesized by electrostatic adsorption through using ZIF-8 as the precursor. Then the ultrathin Ni layer with about 7 nm was deposited on the surface of ZnO/TiO2 (Ni/ZnO/TiO2) by vacuum thermal evaporation method. The Ni/ZnO/TiO2 photoelectrodes showed the highest photocurrent than ZnO/TiO2, Ni/ TiO2 and pure TiO2 photoelectrodes. The durability of Ni/ZnO/TiO2 photoelectrodes was keeping for 10 h in multiple electrolyte solutions under AM 1.5 G illumination and the photocurrent decline can be ignored. The UV–vis absorption spectra demonstrated that the ultrathin Ni layer showed plasma with ZnO/TiO2 for enhancing the water splitting performance. Furthermore, the ultrathin Ni layer enhanced the photogenerated charges transfer for improving the PEC performance. This work provides a new method for ultrathin metal Ni layer with Ovac semiconductor photoelectrode to improve the PEC performance in multiple electrolyte solutions.