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

Solar energy driven photocatalytic hydrogen (H-2) 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 (Ni-6(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 mu mol g(-1)cat 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 Ni-6/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.

Automated summary

This study developed a benzyl thiol protected nickel nanocluster as a co-catalyst for photocatalytic hydrogen evolution over TiO2 catalyst, achieving a thirty times enhancement of hydrogen evolution efficiency by depositing the nanocluster on the TiO2 surface. The presence of visible light could not solely simulate catalytic activity, but it could promote the hydrogen evolution efficiency of Ni-6/TiO2 under ultraviolet irradiation.