ADSORPTION-KINETICS ON CHEMICALLY-MODIFIED OR BIMETALLIC SURFACES

Surface adatom modifiers that act as promoters or poisons on transitio n metal catalysts can have a large influence on adsorption kinetics al ong with their influence on adsorption energetics. Accounting for this effect requires recognition of the role of a new kind of intrinsic pr ecursor -the modifier precursor state. A mathematical description of t he adsorption kinetics of molecules on chemically modified or bimetall ic surfaces incorporating this state has been derived based on Kisliuk 's statistical model [P. Kisliuk, J. Phys. Chem. Solids 3, 95 (1957)]. The resulting equation can be used to explain satisfactorily data on CO adsorption kinetics on chemically modified (Cl-, P-, S-, H-, O-, an d K-precovered) Pt(111) surfaces. This concept should have broad impli cations for many systems in heterogeneous catalysis, such as bimetalli c and alloy surfaces and coadsorbed layers, and for the multicomponent surfaces that are involved in materials growth and processing.