Entropy of adsorption of carbon monoxide on energetically heterogeneous surfaces

Standard entropies of adsorption (Delta s(0)) of CO on different materials (Cu catalysts, Au catalysts, ZnO and to TiO2) are obtained from static adsorption microcalorimetry, adsorption isobars and temperature-programmed desorption, based on the thermodynamics of adsorption on energetically heterogeneous surfaces. Vibrational entropies of the surfaces s(vib)(sigma) are normally between the rotational and the standard translational entropy of CO in gas phase, and decrease with increasing adsorption energy, which agrees with the explanation of statistical thermodynamics. Delta s(0) reflects both the mobility of adsorbates and the specific adsorbate-adsorbent interaction. Limits for reasonable values of the entropy of adsorption are proposed.