The electrochemical hydrogen storage properties of Ti0.72Zr0.28Mn1.6V0.4 alloy synthesized by vacuum plasma spraying and vacuum copper boat induction melting: A comparative study

In this study, two different rapid solidification techniques; vacuum plasma spraying and vacuum copper boat induction melting, were performed to synthesize Ti0.72Zr0.28Mn1.6V0.4 hydrogen storage alloy. The structure and electrochemical properties of the produced samples were comparatively investigated. The chemical and phase compositions of the samples were characterized by XRD and SEM analysis. The electrochemical hydrogen storage characteristics including the cyclic stability, the maximum discharge capacity, the high rate dischargeability, and the electrochemical impedance spectra (EIS) were measured. Results indicated that both samples consisted of a hexagonal C14 Laves phase matrix and a body centered cubic (BCC) structure of V-based solid solution phase. The electrochemical results showed that in the alloy prepared by induction melting, the maximum discharge capacity was higher, while the cyclic stability of the vacuum plasma sprayed sample was much better. These results were attributed to the quantity and distribution of the presence phases and the anti-corrosion performance of the alloys. Moreover, the results from the electrochemical kinetic experiments showed that the vacuum plasma sprayed sample had superior kinetic parameters, including the hydrogen diffusion rate and charge-transfer resistance, than that for the vacuum induction melted sample. Thus, vacuum plasma spraying could be an efficient production method for preparation of hydrogen storage alloys with improved properties which could be used for Ni-MH secondary batteries as negative electrodes.