Graphitic Carbon Nitride for Photocatalytic Air Treatment

Graphitic carbon nitride (g-C(3)N(4)) is a conjugated polymer, which recently drew a lot of attention as a metal-free and UV and visible light responsive photocatalyst in the field of solar energy conversion and environmental remediation. This is due to its appealing electronic band structure, high physicochemical stability and earth-abundant nature. In the present work, bulk g-C(3)N(4) was synthesized by thermal decomposition of melamine. This material was further exfoliated by thermal treatment. S-doped samples were prepared from thiourea or further treatment of exfoliated g-C(3)N(4) by mesylchloride. Synthesized materials were applied for photocatalytic removal of air pollutants (acetaldehyde and NO(x)) according to the ISO 22197 and ISO 22197-1 methodology. The efficiency of acetaldehyde removal under UV irradiation was negligible for all g-C(3)N(4) samples. This can be explained by the fact that g-C(3)N(4) under irradiation does not directly form hydroxyl radicals, which are the primary oxidation species in acetaldehyde oxidation. It was proved by electron paramagnetic resonance (EPR) spectroscopy that the dominant species formed on the irradiated surface of g-C(3)N(4) was the superoxide radical. Its production was responsible for a very high NO(x) removal efficiency not only under UV irradiation (which was comparable with that of TiO(2)), but also under visible irradiation.