Interface control and catalytic performances of Au-NiSx heterostructures

Nickel sulfides (NiSx) as promising catalysts for hydrogen evolution reaction (HER) have attracted much interest. However, the HER catalytic activities of NiSx reported are relatively low for their poor electrical conductivity. The HER catalytic performance of NiSx is expected to be further enhanced by increasing their electronic conductivity. Constructing heterostructures consisting of noble metal and semiconductor has been proven to be an efficient method to promote their physicochemical performances benefitting from synergistic effects along the metal-semiconductor interface. Here, Au-NiSx heterostructures including core@shell, yolk-shell, and oligomer-like structures have been designed and synthesized by different solvothermal methods. A formation mechanism involving the Kirkendall effect has been proposed for the yolk-shell structure with an empty space around the Au core rather than the seeded grown core@shell structure. Catalytic performance measurements indicate that the Au@NiSx core@shell nanoparticles (NPs) exhibit superior HER catalytic property to Au-NiSx yolk-shell, oligomer-like structures, and "pure" NiSx NPs, resulting from the electron transfer between Au and NiSx interfaces. The overpotentials of Au-NiSx NPs with core@shell and yolk-shell nanostructures are 253 mV and 263 mV at 10 mA/cm(2), respectively, which are lower than those of oligomer-like Au-NiSx (283 mV) and pure NiSx (321 mV) NPs. The Tafel slope of Au@NiSx core@shell structure (43.7 mV/dec) is also the lowest. These results demonstrate that the core@shell NPs possess the best HER performances, followed by their yolk-shell and oligomer-like counterparts. These findings confirm that the physicochemical performances of the metal-semiconductor heterostructures can be efficiently optimized by adjusting the electron transfer through the interface structure control.