What do the different types of catalysts do?

Positive catalysts

Positive catalysts are substances that increase the rate of reaction. They do this by lowering the activation energy barrier, making it easier for a large number of substrate molecules to bind to their active site. This enables more reaction molecules to be converted into products, increasing the percentage of product yield and the rate of reaction. 

Example of positive catalyst: Iron oxide acts as a positive catalyst in the synthesis of ammonia (NH3) by Haber’s process, increasing the yield of ammonia, despite less nitrogen reaction. 

Negative catalysts

Negative catalysts are substances that decrease the rate of reaction. They do this by increasing the activation energy barrier, making it more difficult for substrate molecules to bind to their active site. This decreases the number of reactant molecules that can be converted into products, reducing the percentage of product yield and the rate of reaction. 

Example of negative catalyst: Acetanilide acts as a negative catalyst in the decomposition of hydrogen peroxide (H2O2) into water and oxygen, slowing down the rate of hydrogen peroxide decomposition.