Is There a Temperature Effect in Photochemical Reactions

Although the concept of catalysis by light is quite wrong, photoactivated catalysis does exist but here the catalyst is not light, it is an electronically excited molecule which is indeed recovered unchanged (but in its ground state) after the reaction. Such a catalyst is active only in its excited state. 

The following scheme illustrates the process of photoactivated catalysis, C being the catalyst for a reaction R — P 

Sensitized photo-oxidation reactions are an example of such photoactivated catalysis (Section 4.5) in which C would be a dye which absorbs light and forms excited oxygen molecules (P) through energy transfer these excited oxygen molecules then lead to various oxidation reactions. There are other important examples of photoactivated catalysis in photoelectrochemistry (section 4.5.1). 

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