Construction of Co9S8/MoS2 Heterostructures for Enhancing Electrocatalytic Hydrogen Evolution Reaction

The large-scale use of coal, oil, and natural gas will cause environmental pollution and resource shortages, which is incompatible with the sustainable development. Therefore, it is essential to the development of renewable energy. H-2 has a high heat of combustion, and it's combustion products do not include greenhouse gases. so it is considered as an ideal clean energy carrier. Industrial hydrogen production methods will bring CO2 inevitably. As an emerging energy conversion device, hydrogen produced by water splitting has simple equipment and little pollution, making it the first choice for clean energy in the future. Generally, the adsorption energy of hydrogen on the surface of precious metal catalysts is close to zero, and its hydrogen evolution reaction (HER) performance is the most prominent. Pt is an excellent HER catalyst. Commercial Pt/C has high alkaline HER performance, but its higher cost, material instability and resource scarcity limit its widespread applications. Therefore, this research is devoted to the development of high-activity, low-cost transition metal catalysts for HER by water splitting. Firstly, CoMoO4 nanorods were synthesized by hydrothermal method. Then, using the precursor morphology oriented strategy method, the activated Co9S8/MoS2 heterostructure catalyst was successfully prepared by sulfurating Co-MoO4 into CoS2/MoS2 and further, calcining CoS2/MoS2 nanorod in hydrogen atmosphere. X-rays diffraction (XRD), transmission electron microscopy (TEM), electron spin resonance (ESR), Raman spectra, X-ray photoelectron spectra (XPS) and synchrotron-based X-ray absorption fine structure (XAFS) characterizations exhibit that the Co coordination mode change from octahedron in CoS2 to tetrahedron in Co9S8, leading to the activation of inert basal plane in MoS2. Owing to this activation, the interlayer spacing of MoS2 is reduced and thus generate abundant defects. Meanwhile, the increased electrochemical surface area (ECSA) and roughness of the catalysts are more conducive to the adsorption of H*. The test of the contact angle data show that the electrode has good hydrophilicity, which can facilitate the penetration of electrolyte and diffusion of gas molecules quickly. When the current density is at 10 mA.cm(-2) in 1 KOH solution, an overpotential of 84 mV and a Tafel slope of 93 mV.dec(-1) can be achieved. Due to the strong interaction between different components of the heterostructures, the nanorods possess good structural stability in alkaline solutions. This work highlights the vital role of the sulfides heterostructure construction in HER, opening a new way to advanced alkaline HER catalysts.