Catalysts are materials that speed up reactions by providing a different channel for bond breaking and formation. The lower activation energy required for this alternate pathway than for the uncatalyzed reaction is crucial. Catalysts are frequently specific for a single reaction, and this is especially true for enzymes that catalyze biological reactions, such as biofuels produced from the fermentation of carbohydrates. Catalysts are exploited in the synthesis of almost all compounds, and have revolutionized the chemical industry.
A homogeneous catalyst is one in which the catalyst and the reactants are in the same phase. A heterogeneous catalyst, on the other hand, is in a distinct phase from the reactants and products, and is frequently used in industry since it is easy to separate from the products, however it is less specific and allows for side reactions.