摘要/Abstract

利用前驱物形貌导向法，成功制备了Co₉S₈/MoS₂异质结构催化剂，该催化剂在碱性析氢反应（HER）中表现出优异的催化活性及稳定性，其在10 mA·cm^-2处的过电势仅为84 mV.通过X射线粉末衍射（XRD）、透射电子显微镜（TEM）、电子自旋共振（ESR）、拉曼光谱（Raman）、X射线光电子能谱（XPS）和同步辐射（XAFS）等表征，证明了CoS₂/MoS₂在H₂氛围下煅烧形成Co₉S₈/MoS₂的过程中，CoS₂中Co的配位模式从部分八面体向Co₉S₈中的四面体转变，这种转变可活化MoS₂的惰性平面，从而使其更有利于吸附H^*.除此之外，接触角数据表明：该催化剂具有良好的亲水性，有利于电解液渗透及气体分子的迅速扩散，从而促进HER反应速率.由于异质结构间具有强烈的相互作用，该催化剂可表现出良好的结构稳定性.本工作基于Co₉S₈/MoS₂异质结构的成功构筑及对其HER催化机理的充分探讨，为后续硫化物异质结及其在电催化中的应用提供了良好的思路和研究基础.
关键词: 形貌导向法, Co₉S₈/MoS₂, 异质结构, 亲水性, 析氢反应
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. H₂ 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 CoMoO₄ 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 mol·L^-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.
Key words: morphology oriented strategy, Co₉S₈/MoS₂, heterostructure, hydrophilicity, hydrogen evolution reaction


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