Abstract:

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.

Key words: Sodium borohydride, Hydrolysis, Hydrogen generation, Cobalt boride, Non-crystalline structure, Solvent effect