Photoacoustic assessment of oscillations in water vapor desorption from nanostructured catalytic surfaces

In this Letter, we report on the short and long term dynamical behavior of water vapor sorption–desorption cycling on catalytic active nanoclustered Pd:Ag particles packed into compressed thin wafers. The water vapor desorption kinetics, following a hydration session, was monitored using conventional photoacoustic (PA) detection and relative humidity monitoring. It was found that the dehydration process was always accompanied by oscillations, with a period of the order of minutes. These observations are tentatively explained in terms of a PA model appropriate for damp porous materials in which we incorporated a term to describe these oscillations as arising from a competition between reactive sorption processes on the Pd:Ag surface.