Facile preparation of NiS/CdS-t composite photocatalyst for hydrogen evolution from aqueous solution of sulphide/sulphite under visible light

Highlights: ► The nanostructured NiS/CdS photocatalyst was prepared by a facile two-step method. ► After aged for six days, the photocatalyst achieved a maximal rate of H₂ evolution. ► The rate of H₂ evolution on NiS(0.14)/CdS-6 is about 33 times that of CdS-6. - Abstract: The nanostructured NiS/CdS-t (t = aging period in day number) composite photocatalysts were prepared by a facile two-step synthesis method. The photocatalytic activity of H₂ evolution over NiS/CdS could be greatly enhanced by changing the aging period of CdS. The NiS/CdS achieved a maximal rate of H₂ evolution when CdS was aged for 6 days before hydrothermal treatment. It was demonstrated that the composite NiS(0.14)/CdS-6 could achieve a H₂ evolution rate up to 1517 μmol h⁻¹ and show high photocatalytic stability for H₂ evolution under long-term light irradiation. The rate of H₂ evolution on NiS(0.14)/CdS-6 is about 7.5 times that of NiS(0.14)/CdS-3 and 33 times that of CdS-6. The notable improvement can be attributed to the fast electron transfer from CdS to NiS, which is proved by the surface photovoltage spectroscopy and photoluminescent measurements, as well as the increasing percentage of hexagonal-CdS in the mixture of cubic and hexagonal CdS