What role does adsorption play in heterogeneous catalysis?

Explanation

In heterogeneous catalysis, generally the reactants are gaseous whereas the catalyst is a solide. The reactant molecules are adsorbed on the surface of the solide catalyst by physical adsorption or chemical adsorption. As a result, the concentration of the reactant molecules on the surface increases and hence the rate of reaction increases. Alternatively, one of the reactant molecules undergoes fragmentation on the surface of the solid catalyst producing active species which react faster. The product molecules in either case have no affinity for the solid catalyst and are desorbed making the surface free for fresh adsorption. This theory is called adsorption theory.