Humanity is engaged in the reduction of the amount of harmful compounds in the environment on a daily basis. The use of photocatalysis and semiconductor photocatalysts has proven to be a useful solution in the recent years. Photocatalysis uses solar energy, which is a cheap and clean source and its quantities are not limited. Polymeric carbon nitride C$_3$N$_4$ has received much attention due to its thermal and chemical stability, suitable band gap (2,7 eV), environmental friendliness and undemanding synthesis. This work deals with the synthesis of layered C$_3$N$_4$ (g-CN)—undoped and noble metal-doped—and appropriate analyses to characterise each prepared photocatalyst and test its activity. The molecular structure and crystallinity of photocatalysts remain unchanged when doped with silver or palladium, but their surface area increases. The rate of the charge carrier recombination is reduced in most of the doped photocatalysts compared to g-CN. It was demonstrated by EPR analysis that the generation of photoelectrons under light and their amount is greater in most of the doped photocatalysts than in g-CN. Doping also affects the lifetime of charge carriers. We determined which oxygen species are formed. It turns out that Pd-doped photocatalysts generate more ˙OH radicals than g-CN and Ag g-CN. In contrast, the generation of ˙O2$^–$/e$^–$ with Pd g-CN practically does not occur, the same is observed with g-CN. The generation of ˙O2$^–$/e$^–$ is greater in Ag g-CN, especially in photocatalysts treated in a hydrogen atmosphere. Most doped photocatalysts are capable of greater degradation of the pollutant (BPA) than g-CN. Doping with noble metals therefore helps to improve the activity of the photocatalyst.
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