Vertically aligned NiS2/CoS2/MoS2 nanosheet array as an efficient and low-cost electrocatalyst for hydrogen evolution reaction in alkaline media

Recently, the rational design of non-precious metal electrocatalysts for highly efficient hydrogen evolution reaction (HER) in alkaline media has received considerable interests in sustainable and renewable energy researches. Herein, vertically aligned and interconnected NiS2/CoS2/MoS2 nanosheet arrays on Ni foam were prepared by a two-step procedure that conducted by the hydrothermal synthesis of Ni-Co molybdate nanosheet array as the precursor and followed by the vapor phase sulfurization to achieve in situ conversion. Basing on the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations, it can be found that the honeycomb-like structure of the Ni-Co molybdate nanosheet array was well preserved after the sulfurization process. The high-resolution TEM (HRTEM) characterization reveals that the NiS2/CoS2/MoS2 nanosheet array provided abundant well-exposed active edge sites and multiple heterointerfaces towards enhanced alkaline HER performance. Electrochemical studies demonstrated that the ultrathin NiS2/CoS2/MoS2 nanosheets exhibited excellent HER performance with an overpotential of 112 mV at 10 mA cm-2 and a smaller Tafel slope of 59 mV dec-1 in comparison with NiS2/MoS2 (155 mV and 89 mV dec-1) and CoS2/MoS2 (124 mV and 75 mV dec-1) samples by taking the advantage of the well-exposed multiple heterointerfaces. This work presents a facile and reliable synthetic strategy for the rational design of highly efficient electrocatalysts for the HER in alkaline solution based on non-precious metal sulfide nanocomposite.