Influence of metal coatings on charging/discharging processes at hydrogen-absorbing alloy electrodes

D.R. BARSELLINI; A. VISINTIN; W.E. TRIACA

Journal of the Argentine Chemical Society

Asociación Química Argentina

Lugar: Buenos Aires; Año: 2003 vol. 91 p. 183 - 191

0365-0375

The electrochemical behavior of uncoated and Pd-coated AB5-type alloy electrodes in alkaline solution was evaluated. Results show that metal-coated alloys with a low Pd content < 10 wt % exhibit fast activation under charge/discharge cycling and present higher discharge capacities and rate capabilities than the uncoated alloy. The exchange currents per unit of mass for different Pd-coated alloy electrodes were obtained from the slopes of linear polarization curves. For coated alloys with a low Pd content the exchange currents are significantly higher than that for the uncoated alloy. The faster kinetics of hydrogen absorption/desorption processes at Pd-coated alloy electrodes is related to the electrocatalytic effect of Pd on the charge transfer process at the electrode/electrolyte interface, which controls the overall reaction rate.