What is Photocatalysis?
'''Photocatalysis''' is using light as a [[catalyst]] to increase the rate of a photoreaction. Most known photoreactions begin when light creates a [[free radical]] in the reaction system. Light can have a lot of energy and is able to break chemical bonds. For example some things fade or lose their color when left in sunlight. When light breaks the chemical bonds, free radicals are produced. A free radical is a [[molecule]], [[atom]] or an [[ion]] that needs an [[electron]]. The free radical will take electrons from other molecules or atoms and this starts [[chemical reaction]]s.<ref>[https://www.sciencedirect.com/topics/earth-and-planetary-sciences/photocatalysis#:~:text=Photocatalysis%20is%20a%20photo-activated,have%20sufficiently%20high%20energy%20levels. https://www.sciencedirect.com/topics/earth-and-planetary-sciences/photocatalysis#:~:text=Photocatalysis%20is%20a%20photo-activated,have%20sufficiently%20high%20energy%20levels.]</ref> == Terms and background == '''Photo'''- is a prefix showing that light is involved. '''Photolysis''' is when light cuts (breaks bonds) of a molecule. In a chemical reaction there are reactants also called [[reagent]]s that you begin with. Once the reaction takes place you have products. In the example below [[methane]] (CH<sub>4</sub>) and [[oxygen]] (O<sub>2</sub>) are the reactants and [[carbon dioxide]] (CO<sub>2</sub>) and water (H<sub>2</sub>O) are the products. ''CH<sub>4</sub> + 2O<sub>2</sub> → CO<sub>2</sub> + 2H<sub>2</sub>O'' ==Catalysis== Catalysis is using a catalyst to change the rate of a chemical reaction. For the reactants to become the products the reaction must overcome an energy barrier. This energy barrier is known as the activation energy (E<sub>a</sub>). For example, when you lit the methane gas you are providing the activation energy to burn(react). ==Rate== Rate is how fast or slow a chemical reaction happens. ==Catalyst== Catalyst is a substance present but not consumed in a reaction like the other reagents while increasing the rate of the