Corrosion Behaviors of Mg 0.9-xTi 0.1Pd xNi( x=0.04-0.1) Hydrogen Storage Alloy Electrodes

Abstract

The effects of partial substitution of Pd for Mg on the corrosion behaviors of Mg 0.9- x Ti 0.1Pd x Ni ( x=0.04-0.1) hydrogen storage alloys were studied in this paper. The alloys were prepared by mechanical alloying. The alloy structures became amorphous after ball milling for 120 h, which was confirmed by XRD and TEM analysis. The cyclic charge-discharge tests showed that the Pd addition prolonged the cycle life of the alloys effectively. The corrosion performances of the alloys were investigated by open circuit potential measurements, anodic polarization, electrochemical impedance spectroscopy, and XPS experiments. The increase of Pd content shifted the alloy corrosion potentials towards more positive values. The initial corrosion currents of the alloys and its increment rates along with cycle number decreased with the increase of Pd content in the alloys. The measured electrochemical impedance spectra were fitted well with the proposed equivalent circuit model. The analysis suggested that the thickness and the resistance of passive film on the surface of alloys increased with the increase of Pd content in the alloys. The results of XPS experiments demonstrated that the addition of Pd in the alloys suppressed the oxidation and enhanced the anti-corrosion capabilities of the alloys. When the Pd content reached 0.1, the corrosion resistant performances of Mg 0.9- x Ti 0.1Pd x Ni( x=0.04-0.1) alloys are the best and the discharge capacity retention rate is the highest in the present study.