The ratio of the number of atoms of the active component exposed on the catalyst surface to the total number of atoms in the catalyst.

There are physical and chemical methods for the determination of dispersion:

The physical method is to directly observe the particle size (through the electron microscope or XRD), and calculate the dispersion of metal through the formula.

The first mock exam is to adsorb a model molecule selectively on the surface of precious metal (the premise is to accurately understand its stoichiometry). By calculating the adsorbed gas molecules, the number of atoms on the surface of the metal can be calculated. It is common to have H2 and CO molecules as model gases.