Cobalt Sulfide Nanotubes (Co₉S₈) Decorated with Amorphous MoS_x as Highly Efficient Hydrogen Evolution Electrocatalyst

In this paper, we rationally designed a novel hybrid material consisting of Co9S8 nanotubes decorated with molybdenum sulfide lamellae (Co9S8/MoSx), which was synthesized by consecutive solvothermal treatments. The extensive characterizations of the material using X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy (TEM), and high-resolution TEM analyses certified that the decoration was amorphous MoSx. The analysis of X-ray photoelectron spectra suggested the existence of a strong interface interaction between the two phases (Co9S8 and MoSx). Subsequently investigated as an electrocatalyst for the hydrogen evolution reaction (HER) in acid media, the Co9S8/MoSx hybrid exhibited a better activity than pristine MoSx and Co9S8, requiring an overpotential of −161 mV to drive a current density of −10 mA cm–2, as well as higher stability of the performance than Co9S8. Through experimental analysis, it was established that the improved HER activity and stability of the hybrid mainly resulted from the electrocatalytic synergistic effects between Co9S8 and MoSx.