Boosting hydrogen evolution over Ni6(SCH2Ph)12 nanocluster modified TiO2 via pseudo-Z-scheme interfacial charge transfer

Abstract

Solar energy driven photocatalytic hydrogen (H2) evolution over nanocluster modified semiconductor-based photocatalysts and understanding the charge transfer between the interface of nanocluster and semiconductor is of great importance. In this work, a benzyl thiol protected nickel nanocluster (Ni6(SCH2Ph)12) is developed as co-catalyst for the photocatalytic hydrogen evolution over TiO2 catalyst. By mildly depositing the nanocluster onto the TiO2 surface, a thirty times enhancement of hydrogen evolution efficiency and an evolution rate of 5600 μmol g−1cat h−1 is achieved under simulated sunlight irradiation. It is found that the presence of visible light could not simulate catalytic activity solely, however, it could be a promoter to improve the hydrogen evolution efficiency of Ni6/TiO2 upon ultraviolet irradiation. The boosting photocatalytic hydrogen evolution is ascribed to the efficient electron transfer from TiO2 to the nanocluster via a dynamic excitation and electron-hole recombination process assisted by the benzyl group of the ligands, which is evidenced by experimental characterizations and DFT calculations. A pseudo-Z-scheme charge transfer route under simulated solar light irradiation is proposed to illustrate the enhancement of heterogeneous photocatalysis.