Cobalt-boron amorphous alloy prepared in water/cetyl-trimethyl-ammonium bromide/n-hexanol microemulsion as anode for alkaline secondary batteries

Amorphous cobalt-boron (Co-B) with uniform nanoparticles was prepared for the first time via reduction of cobalt acetate by potassium borohydride in the water/cetyl-trimethyl-ammonium bromide/n-hexanol microemulsion system. The sample was characterized by X-ray diffraction, transmission electron microscopy, nitrogen adsorption-desorption, X-ray photoelectron spectroscopy, inductively coupled plasma, cyclic voltammetry, differential scanning calorimetry, temperature-programmed desorption. scanning electron microscopy, charge-discharge test and electrochemical impedance spectra. The results demonstrate that electrochemical activity of the as-synthesized Co-B was higher than that of the regular Co-B prepared in aqueous solution. It indicates that the homogeneous distribution and large specific surface area helped the electrochemical hydrogen storage of the as-synthesized Co-B. Furthermore, the as-synthesized Co-B even had 347 mAh g(-1) after 50 cycles, while the regular Co-B prepared in aqueous solution only had 254 mAh g(-1) after 30 cycles at a current of 100 mA g(-1). The better cycling performance can be ascribed to its smaller interfacial impedance between electrode and electrolyte. (C) 2009 Elsevier Ltd. All rights reserved.