Photocatalysis
Catalyst is a substance present but not consumed in a reaction like the other reagents while increasing the rate of the reaction. The graph below shows the catalyst’s effect on the activation energy. The Y (vertical) axis shows the activation energy while the x (horizontal) axis shows the reaction over time.  With no catalyst present (black line) the reaction has a higher energy to overcome. In the presence of a catalyst (red line) the activation energy is reduced.