Design and fabrication of NiS decorating 2D ultra-thin TiO2 thin film nanocomposites with enhanced photocatalytic hydrogen evolution activity

A novel p-n heterostructural film photocatalyst of oriented NiS/TiO2 nanosheets arrays was designed and successfully fabricated via a simple spin coating technique and its photodegradation activities of hydrogen (H-2) evolution were investigated in detail. The physical and chemical properties of the as-obtained NiS/TiO2 nanosheets samples were investigated by a variety of analytical techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Raman, UV-Vis spectra, photoluminescence (PL), N-2 adsorption-desorption and X-ray photoelectron spectra (XPS). Combining p-type NiS with n-type TiO2 nanosheets to construct distributed p-n heterojunctions, the absorption edge of NiS/TiO2 red-shifted to about 481 nm and its photoresponse in visible range significantly enhanced and the optical band gap in reduced from 3.14 to 2.55 eV. The 10-NiS/TiO2 composite films showed higher surface area (112.3 m(2)/g) than compared with pristine NiS (66.5 m(2)/g) and TiO2 (77.1 m(2)/g). The optimum NiS loading content was found to be 10 wt% and the corresponding hydrogen production rate is ca.7481.1 mu molh(-1) g(-1), being about 17 times higher than that of pure TiO2 (450.4 mu molh(-1) g(-1)). Correlation analysis suggests that the excellent H-2 photocatalytic activity of the NiS/TiO2 p-n heterostructures would stem from the synergy effects between the high efficient charge separation and transfer driven by the built-in electric field at interfaces of NiS/TiO2.