The given blank can be filled with catalysts.
Catalysis refers to the procedure of enhancing the rate of a chemical reaction by supplementing a substance called catalyst. It is not expended in the catalyzed reaction and can spontaneously function regularly. Due to this, only a minute concentration of catalysts are needed to change the rate of reaction in principle.
Usually, the chemical reactions take place briskly in the existence of a catalyst as the catalyst offers an unconventional reaction mechanism with a lesser activation energy in comparison to the non-catalyzed mechanism.