Materials that slows down chemical reactions?

Answer 1

In biological chemical reactions, examples of these are called enzyme inhibitors. Enzymes speed up reactions, but enzyme inhibitors slow them down. This can be by either competing with the reactants for a spot on the enzyme, or by altering the enzyme's structure so that it does not speed up reactions anymore. In either case, enzyme inhibitors slow down chemical reactions.

Answer 2

Substances like inhibitors and catalysts can slow down chemical reactions by interfering with the reaction pathway or by providing an alternative reaction pathway with a higher activation energy. Other materials that can slow down reactions include certain solvents or diluents that reduce the collision frequency of reactant molecules.