Effect of Argon Ion-Bombardment on Adsorption and Exchange Reaction of Hydrogen by Evaporated Nickel Films

Effect of activating treatment on the evaporated films of nickel has been investigated on hydrogen adsorption and hydrogen-deuterium exchange reaction in the pressure range of 10-6–10-3 Torr at room temperature. Adsorbed hydrogen can be distinguished into reversible and irreversible parts, the former can be removed easily by pumping at room temperature and the latter can not. Freundlich isotherm is applicable to the reversible hydrogen and the irreversible adsorption is decribed by Langmuir isotherm with dissociation. The ion-bombardment gave drastical increases of hydrogen adsorption, although surface area of nickel film measured by xenon adsorption showed no change by both bombardment and annealing. The rate of exchange reaction was found to obey the rate law, V = kP1.3 in the both cases after bombardment and annealing. It is concluded that the rate of the exchange is controlled by the reaction step, 2H(a)irr+D2(a)rev=2 HD, and that small part of the dissociative hydrogen which is adsorbed irreversibly might be effective on the exchange reaction near the room temperature.

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