The Principles of Catalysis

What is a catalyst?

In chemistry, a catalyst is a substance that decreases the activation energy of a chemical reaction without itself being changed at the end of the chemical reaction. Catalysts participate in reactions but are neither reactants nor products of the reaction they catalyse. A catalyst is a substance that can increase the rate of a chemical reaction by interacting with reactant molecules via a pathway that makes the formation of products energetically easier.

How do homogeneous and heterogeneous catalysts differ?

Catalysts can be split into two categories:

Homogeneous catalysts

Homogeneous catalysts are in the same physical state (gas, liquid, solid) as the reactants and products. They may all, for example, be dissolved in a solvent like water or they may all be gases in our atmosphere.


Heterogeneous catalysts

Heterogeneous catalysts are in a different physical state to the reactants and products. For example, the catalyst may be a solid while the reactants and products are gases.