Catalysts are substances that speed up chemical reactions. Catalysts are not consumed during chemical reaction. Catalysts speed up chemical reaction by lowering activitaion energy of the reactants.
Manganese dioxide catalyzes the decomposition of hydrogen peroxide to oxygen and water. Manganese dioxide is not consumed during the decomposition since it is a catalyst.
Manganese speeds up the decomposition of hydrogen peroxide by lowering activation energy of hydrogen peroxide.
