The hydrogen electrode reaction characteristics of thin film electrodes of Ni-based hydrogen storage alloys

Abstract

Film-type electrodes of hydrogen absorbing intermetallic compound and alloys, LaNi 5, Ni 0.11 Ti 0.89, Ni 0.50 Ti 0.50 and Ni 0.76 Ti 0.24 were prepared by a flash evaporation method. The hydrogen electrode reaction characteristics of the LaNi 5 and NiTi alloy films in 1 M NaOH are very similar to each other. The reaction proceeds via the Volmer-Tafel reaction route with mixed rate-determining characteristics. The exchange current densities of the constituent steps, as well as the overall reaction, are in the range of 10 −6 A cm −2 (true). Surface analysis by an XPS technique has shown that La or Ti on the electrode surface exists as an electrocatalytically innert oxide of La 2O 3 or TiO 2. Close similarities of these electrodes with pure Ni electrodes indicate that Ni is responsible for the electrocatalytic activity. No synergistic effect is thus noticeable.