Ultrafine and Well-Dispersed Nickel Nanoparticles with Hierarchical Structure for Catalytically Breaking a Boron–Hydrogen Bond

The catalytic properties of ultrafine metal nanoparticles (NPs) are usually limited by their dispersion of NPs; support is thus needed for ultrafine metal NPs. However, single-dimensional supports cannot exhibit a superior catalytic performance because of the ease of aggregation. In this work, we design a hierarchical structure comprising 0D ultrafine nickel (Ni) NPs, flower-like 3D MoS2 nanosheets (NSs), and 2D graphene for a superior catalytic performance. In this design, flower-like 3D MoS2 NSs were the support backbone for the growth of 0D ultrafine Ni NPs and 2D graphene was used to hamper the aggregation and deformation of MoS2 NSs. The well-dispersed hierarchical structures with great structural stability exhibited excellent catalytic activity for the catalytic hydrolysis of ammonia–borane and catalytic reduction of 4-nitrophenol by sodium borohydride in aqueous solutions. The mechanism behind the catalytic reduction was also elaborated using the in situ Fourier transform infrared spectroscopy technique. This design strategy provides a powerful approach for ultrafine metal NPs to achieve a superior catalytic performance because the composition of the hierarchical structure could be adjusted and replaced. Moreover, the designed 3D hierarchical structure could be extended to other heterogeneous catalysis systems.