In Situ Template-Free Ion-Exchange Process to Prepare Visible-Light-Active g-C3N4/NiS Hybrid Photocatalysts with Enhanced Hydrogen Evolution Activity

Nickel sulfide (NiS) and graphitic carbon nitride (g-C3N4) hybrid photocatalysts were prepared via a simple and reproducible in situ template-free ion-exchange process. The physical and photophysical properties of the g-C3N4/NiS hybrid photocatalysts were characterized by X-ray diffraction (XRD), high-resolution transmission electron microcopy (HRTEM), and ultraviolet visible diffuse reflection spectroscopy (DRS). The photocatalytic hydrogen evolution, photoluminescence spectroscopy (PL), and photoelectrochemical (PEC) experiments indicate that the NiS cocatalysts can efficiently promote the separation of photogenerated charge carriers in g-C3N4 and consequently enhance the H-2 evolution activity. The g-C3N4/NiS-1.5 mol % sample shows the highest photocatalytic activity, and the corresponding H-2 evolution rate is 44.77 mu mol h(-1), which approached that of optimal 2.0 wt % Pt/g-C3N4 (47.61 mu mol h(-1)). A possible photocatalytic mechanism of NiS cocatalysts on the improvement of the photocatalytic performance of g-C3N4 is proposed and supported by PL and PEC results. The g-C3N4/NiS shows high stable photocatalytic hydrogen evolution ability under visible light irradiation.