Influence of noble metal coatings on the kinetics of hydriding- dehydriding processes at hydrogen-absorbing alloy electrodes

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

Tesalónica, Grecia

Congreso; 55rd ISE Annual Meeting; 2004

ISE

The kinetics of hydriding- dehydriding processes at uncoated and noble metal-coated AB5-type alloy electrodes in alkaline solution was studied. 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 infuence of Pt deposits on the performance of the alloy electrodes was also evaluated. 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 the hydriding-dehydriding 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.