Surface modification to control the secondary pollution of photocatalytic nitric oxide removal over monolithic protonated g-C3N4/graphene oxide aerogel

Recently, photocatalytic NO_x treatment has attracted great attention on account of the use of environmental-friendly and tremendous energy source. However, the difficult recovery of most reported powdery photocatalysts and the high generation rate of toxic NO₂ byproduct limit its application. Here, we designed a novel monolithic protonated g-C₃N₄/graphene oxide aerogel through a direct frozen-drying method. A remarkable surface electric charge change of negative g-C₃N₄ to positive protonated g-C₃N₄ can be observed after the protonating treatment, which connects with negative graphene oxide nanosheets through the formation of strong electrostatic self-assembly to accelerate the photogenerated charge carriers transfer. Graphene oxide aerogel acts as a monolithic substrate, which provides abundant porous structure, enhanced visible-light absorption, and electrons transport pathway to improve photocatalytic activity. Importantly, the introduction of H atoms on the N atoms of p-C₃N₄ promotes the activation of oxygen atoms, thus improving the oxidization of NO₂ to nitrate. As a result, protonated g-C₃N₄/graphene oxide aerogel reveals an excellent NO removal ratio (46.1%) and low NO₂ generation (2.4%), demonstrating its excellent promising for air pollution purification. Our current work affords novel innovative insight for the construction of monolithic photocatalysts to control the secondary pollution for environmental remediation.