The electrochemical properties of hydrogen storage composite electrodes

In the present work, new type hydrogen storage composites electrodes Ti 0.9 Zr 0.2 Mn 1.5 Cr 0.3 V 0.3 –x wt% La 0.7 Mg 0.25 Zr 0.05 Ni 2.975 Co 0.525 ( x = 0 , 5 , 10 ) were successively prepared by ball milling method. The structure and electrochemical properties of the composites were investigated by means of XRD, SEM, EDS and electrochemical measurements. It was found that the bulk of the composites still retained the hexagonal C14 Laves structure after short-term ball milling and that the maximum capacity of the composite electrodes was significantly improved to 292.4 and 314.0 mA h/g for x = 5 and 10, respectively, from maximum 48.6 mA h/g of Ti 0.9 Zr 0.2 Mn 1.5 Cr 0.3 V 0.3 alloy electrode. Electrochemical impedance spectra and cyclic voltammograms (CV) measurements revealed that the charge-transfer resistance was reduced with increasing amount of La–Mg-based alloy. The increasing x amount also lifted the values of hydrogen diffusion coefficient D of the composite electrodes obtained by anodic polarization (AP) measurements. These indicated that the La–Mg-based alloy as a surface modifier not only increased the discharge capacity but also improved the charge–discharge kinetics of composite electrode greatly.