Hierarchical structure NiO/CdS for highly performance H2 evolution

In this study, oxygen vacancy-rich ultrathin 2D nanosheets NiO were assembled onto 1D nanorod CdS by a facile solvothermal method for photocatalytic H2 evolution. NiO/CdS with a hierarchical structure exhibits an outstanding photocatalytic activity, the H2 evolution rate of which is as much as 43 mmol/g/h under visible light. According to various characterization results, photocatalytic mechanism about charge transfer process was proposed. Density functional calculations reveal that oxygen vacancies introduce a defect level in the bandgap of NiO, resulting an increased visible light absorption. Furthermore, the formed heterojunction in NiO/CdS efficiently separates the photogenerated holes and electrons, which enhances the photocatalytic activities. Electron spin resonance (ESR) spectrum and X-ray photoelectron spectroscopy (XPS) were carried out to illustrate the existence of oxygen defect. And the mechanism is proposed based on the concentration of Cd2+ ions after photocatalytic reaction. This study paves a new way to design highly efficient heterostructures rationally for photocatalytic H2 evolution.