Studies on the electrochemical properties of MlNi(4.3-x)Co(x)Al(0.7) hydride alloy electrodes

In this paper, the electrochemical properties of MlNi(4.3-x)Co(x)Al(0.7) el ectrode alloys, including high rare dischargeability, exchange current dens ity I-o, limiting current density I-L, and diffusion coefficient of hydroge n in the hydride D-alpha by means of linear polarization, anodic polarizati on, and electrochemical impedance spectroscopy were systematically studied. The results indicate that, with the increase of Co content, the cyclic sta bility is improved markedly, which agrees with previous investigation. Howe ver, activation becomes more difficult, and the high rate dischargeability decreases. The linear polarization and anodic polarization results suggest that the exchange current density I-o and limiting current density I-L decr ease ham the 395 (x=0) to 33 mA g(-1) (x=1.3) and from 2263 (x=0) to 308 mA g(-1), respectively. The electrochemical impedance spectroscopy result als o reveals that the diffusion coefficient of hydrogen in the alloys decrease s rapidly with the increase in Co content in MlNi(4.3-x)C(x)Al(0.7) hydride alloy electrodes. (C) 1999 Elsevier Science S.A. All rights reserved.