The absorption of hydrogen and deuterium in thin palladium electrodes: Part II: Basic solutions

Abstract

A comparative study of hydrogen and deuterium sorption in Pd from basic solutions (0.1 M NaOH, NaOD, LiOH and LiOD) has been performed, using electrodes obtained by electrochemical deposition of palladium on gold. The amount of absorbed hydrogen or deuterium has been found to depend on the electrode potential. The shape of H(D)/Pd vs. E plots and the rate of hydrogen (or deuterium) absorption are strongly influenced by the composition of the solution. Lithium appears to have a marked influence on the α to β phase transition. The maximum H(D)/Pd ratios were about 0.8 for all studied solutions. The greater isotopic effect has been found during absorption and desorption in lithium solutions. 1. 1. The amount of absorbed hydrogen-deuterium in the bulk of palladium depends on the electrode potential. 2. 2. The shape of the plots of absorbed hydrogen amount from basic solutions vs. absorption potential strongly depends on composition of solution and significantly differs from the shape of the same plots in acidic solution (2). The results show that alkali metal cations markedly influence hydrogen and deuterium sorption processes. 3. 3. Lithium ions seem to affect the α-β transition more than sodium ions. 4. 4. The isotopic effect is much stronger during oxidation of absorbed hydrogen than during absorption. This effect is greater in lithium solutions. 5. 5. No significant influence of solution composition on the maximum values of the H(D)/Pd ratios has been found. 6. 6. The charging curves in all the solutions studied are not reversible, as was the case in acidic solutions. This means that the sorption or desorption causes irreversible changes in the Pd lattice.