Hydrogen Detection during Catalytic Surface Reactions: Evidence for Activated Lateral Hydrogen Mobility in the Water-Forming Reaction on Pd

By use of a Pd-Si${\mathrm{O}}_2$-Si structure as a hydrogen sensor, very small changes in the hydrogen pressure can be detected. Furthermore, such a structure can be used to detect hydrogen with perfect discrimination during a catalytic surface reaction. By using this technique, together with work-function and desorption measurements, in the study of the water-forming reaction on Pd, we conclude that hydrogen has an activated lateral mobility on Pd.