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 P d:Ag particles packed into compressed thin wafers. The water vapor desorpti on kinetics, following a hydration session, was monitored using conventiona l photoacoustic (PA) detection and relative humidity monitoring. It was fou nd that the dehydration process was always accompanied by oscillations, wit h a period of the order of minutes. These observations are tentatively expl ained 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 co mpetition between reactive sorption processes on the Pd:Ag surface. (C) 200 0 Elsevier Science B.V. All rights reserved.