Graphitic Carbon Nitride for Photocatalytic Air Treatment

Abstract

<jats:p>Graphitic carbon nitride (g-C3N4) 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-C3N4 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-C3N4 by mesylchloride. Synthesized materials were applied for photocatalytic removal of air pollutants (acetaldehyde and NOx) according to the ISO 22197 and ISO 22197-1 methodology. The efficiency of acetaldehyde removal under UV irradiation was negligible for all g-C3N4 samples. This can be explained by the fact that g-C3N4 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-C3N4 was the superoxide radical. Its production was responsible for a very high NOx removal efficiency not only under UV irradiation (which was comparable with that of TiO2), but also under visible irradiation.</jats:p>

Immobilization of Exfoliated g-C3N4 for Photocatalytical Removal of Organic Pollutants from Water

“…The position of CB of g-C 3 N 4 is very negative (∼ −1.27 V vs. NHE at pH 7 [29]), which indicates that carbon nitride has strong reductive properties, but the position of the VB (1.39 V vs. NHE at pH 7 [29]) is lower than the potential for the •OH/OHcouple, which means that no formation of •OH takes place on the surface of g-C 3 N 4 . This was confirmed by electron paramagnetic resonance (EPR) spectroscopy in our previous work [15].…”

“…g-C 3 N 4 can also be exfoliated by a chemical method, via redox reactions using different oxidants [11,12]. Exfoliated g-C 3 N 4 exhibits higher photocatalytic activity and can be used in different applications such as water or air cleaning [13][14][15]. For these applications, g-C 3 N 4 can be used in the form of suspensions or films.…”

Rapid and Scalable Fabrication of TiO2@g-C3N4 Heterojunction for Highly Efficient Photocatalytic NO Removal under Visible Light

“…showing an excellent response under visible light, non-toxicity, low cost, and ease of fabrication. 73 (Yu et al, 2016;Wang et al, 2019;Baudys et al, 2020;Van Viet et al, 2021b;,…”

Comparison of Graphitic Carbon Nitrides Synthetized from Melamine and Melamine-Cyanurate Complex: Characterization and Photocatalytic Decomposition of Ofloxacin and Ampicillin

“…Comparing these results with the standard redox potentials of superoxide and hydroxyl radicals E o (OH•/H 2 O) = 2.74 V and E o (O 2 /O 2 •− ) = −0.33 V at pH = 7 [ 52 ], one can see that the reaction of holes with water cannot be performed, unlike the reaction of electrons with oxygen, in which superoxide radicals are formed. Their formation was confirmed by electron paramagnetic resonance (EPR) in our previous work [ 53 ]. Therefore, the reactions of superoxide radicals forming hydrogen peroxide (E o (H 2 O 2 /H 2 O) = 1.76 V at pH = 7) [ 54 ] and/or hydroxyl radicals (through hydrogen peroxide) [ 39 , 55 ] can be expected because the superoxide radicals themselves are not able to take part in oxidation reactions.…”