1. Catalysis and photocatalysis

Every catalytic reaction requires the use of a catalyst, a substance that initiates the catalytic process and appears both as a reactant and a product of the reaction, i.e. it is restored at the end of the process, and therefore does not appear in the overall reaction balance. In fact, the catalyst is involved in one (or more) stages of the reaction, which explains its influence on the speed of the reaction, and is then regenerated in a subsequent stage. As a result, the catalyst is used in much smaller quantities than the other reagents. What's more, the catalyst has no influence on the composition of the thermodynamic equilibrium at the end of the reaction....