Effects of Electronic Charge Transfer between Adsorbate and Solid on Chemisorption and Catalysis

When chemisorption on a semiconductive solid is accompanied by electronic charge transfer between adsorbate and solid, an electronic boundary layer analogous to that in rectifying junctions may develop and polarization of charges in the solid may result. These phenomena may limit or control the chemisorption characteristics. The boundary layer theory developed for electrical contacts and elementary considerations concerning the effect of the polarization potential are applied to derive the form of relationships for the extent, heats, and rates of chemisorption and some consequences with respect to catalysis. An attempt is made to illustrate the detailed physical processes in order to examine the meaning of ``heterogeneity'' and ``active centers'' in cases of this type of chemisorption.