Multi‐shaped Amorphous Alloy Ni‐B: Ultrasonically Aided Complexing‐reduction Preparation, Catalytic Ability for NaBH₄ Hydrolysis Yielding H₂ Gas

Abstract

Abstract The multi‐shaped amorphous alloy (Ni‐B) powders were prepared by complexing reduction route using sodium borohydride (NaBH 4 ) as reductant with assistance of ultrasonic wave. The selected complexants, i.e. water, ammonia, salicylic acid, and ethylene diamine tetraacetic acid (EDTA) possess sequentially escalating complexation ability. The chemical composition and shapes of the product samples obtained under different conditions were characterized by X‐ray powder differaction, selected area electron diffraction, and transmission electron microscope. The influence of reaction conditions such as the types of Ni‐B, temperatures, NaBH 4 concentrations, and sodium hydroxide (NaOH) content on the hydrogen generation rate of hydrolysis of NaBH 4 solution were investigated in detail. The results show that the as‐prepared Ni‐B powders all belong to amorphous alloy with variable element contents, and the Ni‐B sample prepared from EDTA complexation, possessing the best fineness and dispersity, has the strongest catalytic activity. The mean apparent activation energy of the hydrolysis reaction is 64.90 kJ · mol –1 . The NaBH 4 concentration has little impact on hydrogen generation rate, implying that the catalytic hydrolysis of NaBH 4 solution should be the pseudo zero‐order reaction. Keeping the NaOH content at below 5 % could inhibit the hydrolysis of NaBH 4 solution, but the NaOH contents from 10 % to 15 % will significantly promote the hydrolysis rate of NaBH 4 . The hydrolysis reaction mechanisms, especially the effect of NaOH content on the hydrolysis reaction were also analyzed.