Solvent effects in the synthesis of CoB catalysts on hydrogen generation from hydrolysis of sodium borohydride

Solvent effects are important in synthetic chemistry, especially in preparing nanosized materials in solution. The sizes, morphologies, and properties of nanoparticles obtained from solution are greatly influenced by the solvents used. CoB catalysts were synthesized in solvents with different viscosity and polarity, including water, methanol, ethanol, and n-propanol. Solvent effects on the size and morphology of CoB were investigated using X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), and nitrogen sorption measurements. CoB catalysts possessed non-crystalline structures composed of discrete nanoparticles, but became more agglomerated with increasing solvent viscosity. The hydrolysis of NaBH4 showed that catalyst morphology and texture greatly affected catalytic activity. XPS showed that Co and B were each present in elemental and oxidized states in the CoB catalysts, and that the Co/B surface ratio varied greatly with a higher Co/B ratio resulting in better catalytic properties. Solvent effects were analyzed in terms of steric hindrance and viscosity, and a mechanism for CoB synthesis in the different solvents was proposed.

摘要分别以不同粘度和极性的水、甲醇、乙醇、正丙醇为溶剂制备了钴硼催化剂, 并通过X射线衍射、场发射扫描电镜、透射电镜、X射线光电子能谱和N2吸附等表征手段对溶剂效应进行了深入探索. 所制备的钴硼催化剂具有非晶结构, 且随着溶剂粘度的增加, 粒子团聚现象加剧. 不同溶剂中制备的钴硼催化剂对于硼氢化钠水解产氢反应的活性具有显著差异, XPS测试表明钴元素和硼元素均以元素态及氧化态形式存在, 而且不同溶剂中制备的钴硼催化剂具有不同的表面钴/硼比, 具有高钴/硼比的催化剂有更好的催化性能. 从溶剂的粘度、溶剂分子的空间位阻效应等方面对溶剂效应进行了分析, 并提出了钴硼催化剂在不同溶剂中可能的形成机理.

Graphical AbstractSolvent effects in the synthesis of non-crystalline CoB catalysts on the structures, morphologies, and catalytic properties were studied. A possible mechanism was proposed.Figure optionsDownload as PowerPoint slide