Surface chemistry

Surface chemistry studies chemical processes at interfaces, where local coordination and composition differ from the bulk. Adsorption can concentrate reactants, change their electronic environment and enable surface-mediated catalysis. The active surface can be a solid–gas, solid–liquid or other interface.

For a spherical particle of radius $r$, the surface-area-to-volume ratio is $3/r$. Making particles smaller therefore increases the fraction of material exposed to the environment. This geometric change helps explain why fine particles can react differently from a bulk specimen of the same nominal composition. Surface structure, defects and adsorbed species still matter: geometric area alone does not count chemically active sites.