Studies On The Preparation, Structure And Electrocatalytic Properties Of Ni-based Amorphous Alloys Nanoparticles

The research objectives of this dissertation are to increase antioxidation ability and thermal stability of the Ni-B amorphous alloy nanoclusters,to inhibit its crystallization and agglomeration,and to expand its application field.The main research contents and results are summarized as below:1.The Ni-B and Ni-Mo-B amorphous alloys powders with a size of around 10nm were prepared by chemical reduction with KBH₄ in aqueous solution.The Ni-Mo-B alloy exhibits better thermal stability and stronger antioxidation ability than the Ni-B alloy.2.Electrocatalytic oxidation of methanol,ethanol and propanol on the nanosize Ni-B amorphous alloy powdermicroelectrode in alkaline media was studied with cyclic voltammetry.It is shown that the nanosize Ni-B amorphous alloy powdermicroelectrode has stronger electrocatalytic activities for the oxidation of methanol,ethanol and propanol than Ni nanowire electrode,highly preferred orientation(220)nickel electrode.Compared to highly preferred orientation(220)nickel electrode,in 1 mol·L^-1KOH solution containing primary alcohols,the onset potential of Ni(â…¡)oxidation on the nanosize Ni-B amorphous alloy powdermicroelectrode is negatively shifted about 0.04V with peak potential showing a considerable decrease,and the current densities of Ni(â…¡)oxidation are increased approximately by the 2 orders of magnitude.The kinetic parameters were determined with the steady polarization curves.The results show that the rate constants for the oxidation of methanol,ethanol and propanol by Ni(â…¢),the rate constants for the oxidation of Ni(â…¡)to Ni(â…¢)and the rate constants for the reduction of Ni(â…¢)to Ni(â…¡)on the nanosize Ni-B amorphous alloy powdermicroelectrode are increased by about 2,3,2-3 orders of magnitude,respectively,in comparison with those on the highly preferred orientation(220)nickel electrode. The onset potential and peak potential of Ni(â…¡)oxidation on the nanosize Ni-B amorphous alloy powdermicroelectrode are lower than those on the Ni-B nanocrystalline powdermicroelectrode and the electroless Ni-B amorphous alloy microdisk electrode.Thus,the strong electrocatalytic activity of the nanosize Ni-B amorphous alloy powdermicroelectrode is concerned with its nanometer properties and amorphous properties.3.The nearly monodispersed Ni-B and Ni-La-B amorphous alloys nanoclusters with a size of around 10-15nm and an even size distribution,that is the smallest monodispersed size of the unsupported amorphous alloy nanoclusters so far,were prepared in W/O microemulsion.The crystallization process of Ni-La-B amorphous alloy nanoclusters includes the two steps:one is the transformation of Ni-La-B amorphous alloy into Ni-La-B crystalline alloy,the other is the decomposition of Ni-La-B crystalline alloy into Ni-La nanocrystalline and free B.It is found that the rate of the latter is higher than the former through determining phase transition activation energy.4.The activities of hydrogen adsorption and evolution of the nanosize Ni-B amorphous alloy powdermicroelectrode and its activity of electrocatalytic hydrogenation(ECH)for cyclohexanone are stronger than high surface area nickel microelectrode.The ECH reaction occurs between the weakly chemisorbed H atoms and cyclohexanone.The activity of ECH is depressed by the formation of irreducibleβ-Ni(OH)₂.