Effects of amorphous Co-C on the structural and electrochemical characteristics of La0.8Mg0.2Ni0.8Mn0.1Co0.5Al0.1 hydrogen storage alloy

Amorphous Co-C powder prepared by ball milling was introduced to improve the performance of La0.8Mg0.2Ni0.8Mn0.1Co0.5Al0.1 hydrogen storage alloy. The structural and electrochemical properties of the as-prepared La0.8Mg0.2Ni0.8Mn0.1Co0.5Al0.1-x wt.% Co-C composites were investigated systematically. Scanning electron microscopic images show La0.8Mg0.2Ni0.8Mn0.1Co0.5Al0.1 alloy was coated by Co-C particles. X-ray diffraction patterns suggest that the composite almost remained original phase structures of La0.8Mg0.2Ni0.8Mn0.1Co0.5Al0.1 and Co-C in both charge and discharge processes. The maximum discharge capacity of the composites reached 414 mAh g(-1) at a current density of 50 mA g(-1) at 298 K. The cyclic stability and the discharge capacities of the composite electrodes were noticeably improved in comparison with single La-Mg-Ni-based alloy due to increased corrosion resistance and the catalysis of the Co-C powder. Cyclic voltammogram and potentiodynamic polarization studies on the composite indicate that the electrochemical kinetics was improved and the corrosion resistance was increased. The cycling performance of the composite electrode at high current density is good as well. (c) 2008 Elsevier B.V. All rights reserved.