A Discussion about the Kinetics of Adsorption,Desorption and Exchange Reaction of CO on the Transition Metal Surfaces

A kinetic model is proposed to correlate the adsorption and desorption of CO with the exchange reaction of CO（g） with CO（a） occurring simultaneously on the transition metal surfaces. There are two ways for CO to be adsorbed on the surfaces; Direct sticking or via precursor state. The desorption rate is determined by the exchange reaction rate, proportional to the ambient gas pressure, decreasing with coverage, and increasing with surface temperature. The relationship between the coverage and the exchange reaction cross section reveals why the full coverage can not be achieved. A modified Kisliuk equation is derived, applicable to fit various adsorption curves. All the inferences from the model are comparable to the experimental observations.