In heterogeneous catalysis, the reactants and the catalyst are in different phases, typically solid and gas or liquid. The catalyst is usually a solid material with a high surface area, which provides a large number of active sites for the reactants to adsorb onto and interact with. The role of surface area in heterogeneous catalysis is crucial, as it directly affects the catalytic activity of the substance.A larger surface area means that there are more active sites available for the reactants to adsorb onto, which increases the probability of successful collisions between the reactant molecules and the catalyst's active sites. This, in turn, leads to an increase in the rate of the catalytic reaction, enhancing the overall catalytic activity of the substance.In practical applications, catalysts with high surface areas are often used to improve the efficiency of industrial processes. For example, nanoparticles or porous materials can be employed as catalysts due to their large surface area-to-volume ratios, which provide a high number of active sites for the reactants to interact with.In summary, the surface area of a catalyst plays a significant role in heterogeneous catalysis, as it directly affects the number of active sites available for reactants to interact with. A larger surface area leads to increased catalytic activity, making the reaction more efficient and effective.