In this paper, the structural characterization of the ternary phase Y3 (Fe, Mo)29 compound has been investigated in great detail by refi+L43nement of the X-ray diffraction pattern. The structural relationship of the 3:29 phase with 2:17 and 1:12 phases has been studied according to theoretical calculations and experimental results. The results show that the 3:29 compound belongs to A2/m. space group and the 3:29 compound is a kind of mixed structure of 2:17 and 1:12 structures.

In this paper, the electrochemical properties of MlNi4.3-xCoxA10.7electrode alloys, including high rate dischargeability, exchange current density 10, limiting current density IL, and diffusion coefficient of hydrogen in the hydride Da by means of linear polarization, anodic polarization, and electrochemical impedance spectroscopy were systematically studied. The results indicate that, with the increase of Co content, the cyclic stability is improved markedly, which agrees with previous investigation. However, activation becomes more difficult, and the high rate dischargeability decreases. The linear polarization and anodic polarization results suggest that the exchange 21 current density I0 and limiting current density IL decrease from the 395 (x=0) to 33mAg (x=1.3) and from 2263 (x=0) to 308mA g-1, respectively. The electrochemical impedance spectroscopy result also reveals that the diffusion coefficient of hydrogen in the alloys decreases rapidly with the increase in Co content in MlNi4.3-xCoxAl0.7 hydride alloy electrodes.

In this paper, the degradation mechanism of the Ti-V-based multiphase hydrogen storage electrode alloys (Ti0.8Zr0.2) (V0.533Mn0.107Cr0.16-Ni0.2)x (x=2, 4, 6) during electrochemical cycling has been studied systematically by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and electrochemical impedance spectroscopy (EIS). The reasons for the improvement in cycling stability of the electrodes with increasing x have also been discussed. The results show that the capacity degradation of the electrode is mainly caused by the following two reasons. The first one is the pulverization of the alloy particles during cycling, which leads to an increase in contact resistance and decrease in electric conductivity between alloy particles. The second one is the oxidation and corrosion/dissolution of the active alloy constituents in alkaline electrolyte during cycling, which leads to an increase in surface reaction resistance and decrease in discharge capacity of the alloy electrodes. With increasing x, the portion of stable and inactive hydride formed in the alloy during cycling decreases, and the pulverization resistance

Hydrogenation and dehydrogenation of two different phases in a multiphase Ti-V-based alloy Ti0.8Zr0.2V1.867Mn0.373Cr0.56Ni0.7, namely the C14 Laves phase with hexagonal structure and the V-based solid solution phase with body centered cubic (bcc) structure during electrochemical charging and discharging were investigated by X-ray powder diffraction (XRD) analysis. For the alloy investigated, the C14 Laves phase component, which had good surface electrochemical activity for decomposing water, was hydrogenated from the very beginning of the charging process and was providing hydrogen to both phase components throughout the entire electrochemical charging process. The V-based solid solution phase, which had no or very low surface electrochemical activity for decomposing water during electrochemical charging, could obtain hydrogen only from its neighboring C14 Laves phase component when the hydrogen content of which was high enough to build up an adequate pressure to feed hydrogen to its neighboring phase component. The V-based solid solution phase experienced a phase change when the hydrogen in it reached a definite level, namely from bcc to body centered tetragonal (bct) structure. Probably due to the high stability of bct hydride phase of the V-based solid solution phase, it did not revert back to the initial bcc structure during the electrochemical discharging process conducted in our experiment at the room temperature and atmospheric pressure.

This paper describes the effects of treating the alloy powder of an electrode with 6 MKOH solution containingy M KBH4 (y=0.0, 0.005, 0.01, 0.02 and 0.03) on the kinetic properties of the electrode, including high rate dischargeablilty HRD, exchange current density I0, symmetry factor β, limiting current density IL, diffusion coeffcient of hydrogen in the a-phase Da, and electrochemical polarization ηe and concentration polarization ηc. The results show that the kinetic parameters HRD, 10, IL and Daincrease markedly with the increase in the concentration of KBH4, the ηe and ηc decrease rapidly with increasing concentration of KBH4, but the symmetry factor β does not change.