Today, many chemical reactions are known, the course of which depends not so much on the composition of the reacting substances as on their physical state.
Many of them are impossible without certain conditions.
Photocatalysis reactions also belong to this type.
In the broad sense, photocatalysis is aProcess of multiple (from thousands to millions of times) acceleration of the course of chemical reactions with the simultaneous action of a catalyst substance and light radiation. The peculiarity of photocatalysis consists precisely in the fact that the separate effect of the light radiation or the catalyst on the reagents does not have any significant effect.
There are several types of photocatalysis. In photoinduced catalysis, an increase in the rate of passage of the reaction is provided by a catalyst, which is formed from a previously inactive substance (pre-cusp) under the influence of light. Under certain conditions, similar reactions can occur even after the irradiation has ceased.
Photoactivated catalysis is similar to catalysisPhotoinduced (in it also a catalyst is formed from the precursor under the influence of light). However, during the course of the main reaction, the catalyst is again converted into a pre-cursor. Therefore, constant irradiation is necessary to ensure catalysis.
Catalytic photoreactions as a speciesPhotocatalysis is characterized by the fact that the catalyst in them plays a traditional role. Under the influence of light, the reacting substances change, passing into the so-called excited state. It makes possible their effective interaction with the catalyst. Accordingly, the reaction is only under the influence of light.
Photocatalytic reactions are very commonin nature. The most striking example of natural photocatalysis is photosynthesis. In the chemical industry today photocatalysis is used very widely. With it, various reactions of oxidation, reduction, polymerization of hydrogenation and dehydrogenation, precipitation of metals are accelerated. Based on the effect of photocatalysis, air purification systems are produced.