Structural effects on voltammograms of the low index planes of palladium and Pd(S)-[n(1 0 0) × (1 1 1)] surfaces in alkaline solution

Voltammograms of the low index planes of Pd and Pd(S)-[n(1 0 0) × (1 1 1)] electrodes have been studied in 0.1 M NaOH. The voltammograms are more complicated than those in acid solutions. An anodic peak due to the desorption of absorbed hydrogen is found on Pd(1 1 1) and Pd(1 0 0). No peak due to the hydrogen desorption is observed on Pd(1 1 0). The onset potentials of the oxide film formation are more negative than those in acid solutions. Coverages of the oxide film on Pd(1 1 1) and Pd(1 0 0) in 0.1 M NaOH are lower than those in 0.1 M HClO4. The coverage on Pd(1 1 0), however, has the same value as the one in 0.1 M HClO4. On Pd(S)-[n(1 0 0) × (1 1 1)] electrodes, oxide film formation at the step can be distinguished from the one at the terrace in 0.1 M NaOH. This result differs from that in H2SO4 in which the oxide film formation gives no peak at the step.