What role does adsorption play in heterogeneous catalysis?

(N/A) Heterogeneous catalysis is a process where the catalyst and reactants exist in different phases. The mechanism is explained by the adsorption theory,which involves the following steps:
$i$. Adsorption of reactant molecules onto the surface of the solid catalyst.
$ii$. Occurrence of a chemical reaction on the surface through the formation of an intermediate.
$iii$. Desorption of the reaction products from the catalyst surface.
$iv$. Diffusion of the products away from the catalyst surface.
In this process,the solid catalyst surface provides active sites where the concentration of gaseous reactants increases,thereby increasing the rate of reaction. Once the reaction occurs,the products have a lower affinity for the surface and are desorbed,freeing the active sites for further reactant molecules.