Inhibition in Surface Reactions

When a substance other than the reactants is adsorbed on the concerned surface, the inhibition occurs. This is due to the fact that on adsorption of the substance, the effective surface area is reduced and therefore, the rate is also reduced. 

Let us consider a unimolecular reaction on the surface. Let that at any time, surface covered by reactant (A) is 0 and surface covered by substance (inhibitor) is Gj. Then 

At low pressure of the reactant, KP (1 + WjPj), the above equation reduces to 

Similarly, the inhibition equation can also be derived for a bimolecular surface reaction. Let us consider a reaction between two reactants A and B and inhibition by a inhibitor (I). If Pu P2 and P are the respective partial pressures of A, B and I, then the fractions of the surface covered by A and B are given as 

However, if the inhibitor is a diatomic molecule and adsorbed atomically, 

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