Auto-inhibition of hydrogen gas evolution on gold in aqueous acid solution

It was demonstrated recently that dramatic changes in the redox behaviour o f gold/aqueous solution interfaces may be observed following either cathodi c or thermal electrode pretreatment. Further work on the cathodic pretreatm ent of gold in acid solution revealed that as the activity of the gold surf ace was increased, its performance as a substrate for hydrogen gas evolutio n under constant potential conditions deteriorated. The change in activity of the gold atoms at the interface, which was attributed to a hydrogen embr ittlement process (the occurrence of the latter was subsequently checked by surface microscopy), was confirmed, as in earlier work, by the appearance of a substantial anodic peak at ca. 0.5 V (RHE) in a post-activation positi ve sweep. Changes in the catalytic activity of a metal surface reflect the fact that the structure (or topography), thermodynamic activity and electro nic properties of a surface are dependent not only on pretreatment but also , in the case of the hydrogen evolution reaction, vary with time during the course of reaction. As will be reported shortly, similar land often more d ramatic) time-dependent behaviour was observed for hydrogen gas evolution o n other metal electrodes.