Study on the electrochemical properties of Mg 0.8Ti 0.1Al 0.1 −xPd xNi ( x = 0.02–0.08) hydrogen storage alloys

Abstract

Abstract. The Mg 0.8 Ti 0.1 Al 0.1 −x Pd x Ni ( x = 0.02–0.08) hydrogen storage alloys were prepared by mechanical alloying (MA) and the electrochemical properties of the alloy electrodes were studied systematically. Charge-discharge measurement shows that the maximum discharge capacity decreases from 383.5 mAh g −1 ( x = 0.02) to 360.3 mAh g −1 ( x = 0.08), however, the cycle stability is improved obviously due to the enhancement of the anti-corrosion performance, the capacity retention ratio 100%× C 100 / C 1 increases from 39.6% ( x = 0.02) to 49.0% ( x = 0.04), 58.6% ( x = 0.06) and 58.4% ( x = 0.08), respectively. At the discharge current density 500 mA g −1 , the high rate dischargeability (HRD) increases from 59.2% ( x = 0.02) to 73.5% ( x = 0.08), indicating that the electrochemical kinetics of the alloy electrodes is improved with the increasing of Pd content. In addition, electrochemical impedance spectroscopy (EIS), linear polarization and potentiostatic discharge measurements were also employed to study the kinetics of the alloy electrodes. The results obtained indicate that the electrochemical kinetics of the alloy electrodes is jointly controlled by the charge-transfer reaction rate on the alloy surface and the hydrogen diffusion rate in the bulk of the alloys, and the latter is the rate-determining step of discharge process.