Influences of molybdenum substitution for cobalt on the phase structure and electrochemical kinetic properties of AB5-type hydrogen storage alloys

The effects of the partial replacement of Co with Mo on the phase structure and electrochemical kinetic properties of La0.35Ce0.65Ni3.54Co0.80-xMn0.35Al0.32Mox (x=0.00, 0.10, 0.15, 0.20, 0.25) hydrogen storage alloys prepared by arc-melting method were sys-tematically studied in this paper. The X-ray diffraction (XRD) showed that after partial substitution of Mo for Co, the alloys remained a single LaNi5 phase with a hexagonal CaCu5-type structure. The P-C isotherms indicated that the equilibrium pressure gradually decreased with in-creasing of Mo content. Electrochemical studies showed that the substitution of Mo for Co could greatly increase discharge capacity, improve activation ability and reduce self-discharge of alloy electrodes. The alloy with x=0.25 exhibited a higher rate dischargeability (HRD1200= 50.9%). Moreover, Mo is a vital element in favor of kinetic properties of AB5-type hydrogen storage alloys. As Mo content increased, the ex-change current density I0, the hydrogen diffusion rate gradually increased.