Portal de Periódicos da CAPES

Effect of Co content on the kinetic properties of the MlNi4.3−XCoXAl0.7 hydride electrodes

1999; Elsevier BV; Volume: 44; Issue: 23 Linguagem: Inglês

10.1016/s0013-4686(99)00116-4

1873-3859

Hongge Pan, Jianxin Ma, Chunsheng Wang, C.P Chen, Q.D Wang,

Membrane-based Ion Separation Techniques

By means of linear polarization, Tafel polarization and galvanostatic discharge methods, the kinetic properties of MlNi4.3−XCoXAl0.7 (X=0.0, 0.3, 0.5, 0.7, 0.9, 1.1 and 1.3) hydride electrodes, including high rate dischargeability HRD, exchange current density I0, limiting current density IL, the symmetry factor β, and the apparent diffusion coefficient of hydrogen in the α phase Dα have been studied systematically. The results show that the HRD of the electrode with high Co content is lower than that with low Co content. For the MlNi4.3−XCoXAl0.7 hydride electrodes, with Co content increasing from 0.0 to 1.3, the values of I0, IL, β and Dα decreased from 395 to 33 mA/g, 2263 to 308 mA/g, 0.85 to 0.43, 1.42×10−10 to 2.1×10−11 cm2/s, respectively. In order to calculate the electrochemical polarization ηe and concentration polarization ηc based on anodic polarization curve, the experimental anodic polarization curve should be divided into three regions to discuss according to discharge current density Id, namely, Id< IP, IP<Id If. The calculation of ηe and ηc should use different formula in different regions. When discharge current density Id is smaller than Ip, the traditional equation used to calculate the electrochemical overpotential can not be used, when Ip is between Ip and If, both equations used to calculate the electrochemical overpotential and concentration overpotential can be used, and when Id is larger than If, because there exists absorption and adsorption of hydrogen, the traditional equation used to calculate concentration overpotential can not be used in the system of hydride electrodes.