Electrochemical properties of MmNi3.03Si0.85Co0.60Mn0.31Al0.08 hydrogen storage alloys in alkaline electrolytes—A cyclic voltammetric study at different temperatures

Hydrogen diffusion behavior in α-solid solution phase of LmNi3.55Co0.75Mn0.4Al0.3 metal hydride electrode—Effect of temperature

“…The obtained results were found to be consistent with the reported values for alloy electrodes with the same or similar composition at low concentration of hydrogen initially charged [9,14,[16][17][18]21,24,25]. Conversely, some reports suggest that the values of hydrogen diffusion coefficient are one or maybe two orders of magnitude lower or higher [8,10,11,13,15,[26][27][28]. This great discrepancy in the reported values of hydrogen diffusion coefficient in the alloy electrodes, even with the same composition, might be attributed to the following.…”

“…The reported values for the hydrogen diffusion coefficient in the AB 5 -type intermetallics, being determined for various compositions, vary over seven orders of magnitude (10 −5 to 10 −11 cm 2 s −1 ) [8][9][10][11][12][13][14][15][16][17][18]. Despite this diversity, there is a point upon which various authors agree; the existing decrease of the hydrogen diffusion coefficient, during the discharge of the MH electrode, with an increasing concentration of hydrogen initially absorbed into the alloy electrode [8,9,[12][13][14][15][16][17][18].…”

“…The performance of a MH electrode is determined by both the rate of the hydrogen diffusion process within the bulk of electrode and/or the kinetic of the charge-transfer reaction occurring at the electrode/electrolyte interface [8][9][10][11]. Since hydrogen diffusion may be the rate-determining step, the evaluation of the hydrogen diffusion coefficient (an important diagnostic parameter of this process) may assist in understanding the hydrogen transport phenomena in the MH electrode.…”

Effects of Al content on the electrochemical properties of La0.78Ce0.22Ni3.95-xCo0.65Mn0.3Si0.1Alx alloys at 20–80 °C

“…It is notable that so many flocculent corrosion products appear on the alloy surface at elevated temperature, which was reported as rare earth hydroxides [13,34,35]. The large existence of soluble and insoluble corrosion products over the fresh surfaces clogs the conductive pathways between alloy particles [8], and consequently speeds up the irreversible capacity loss at elevated temperatures. Furthermore, the cracks and flocculent oxidation in the La 0.78 Ce 0.22 Ni 3.95 Mn 0.3 Si 0.1 Co 0.65 free-Al alloy (Fig.…”

Investigations on rate constants of the charging/discharging processes for metal hydride electrodes

“…The electrochemical method is a powerful instrument to research the kinetics performance and a series of them has been utilized to measure the kinetics parameters of hydrogen storage alloys [5][6][7][8]. Among these methods, constant potential and constant current discharge can only be used to measure an average diffusion coefficient from the given depth of discharge (DOD) to fully discharge state (100% DOD), because these methods disregard the dependence of the hydrogen diffusion coefficient on hydrogen concentration in the electrode [9].…”