Unlocking the potential of thermally exfoliated ultrathin g-C3N4 nanosheets: abundant active sites for enhanced solar photocatalysis

Abstract

Tailoring the surface properties of catalysts by introducing various functional groups with superior adsorption properties has been a promising strategy to boost photocatalytic performance. In this study, the thermal exfoliation of graphitic carbon nitride (g-C₃N₄) was utilized to produce ultrathin nanosheets that exhibit a high specific surface area and abundant active sites. The exfoliated g-C₃N₄ nanosheets (CN-600) were produced by heating pristine g-C₃N₄ (CN) in ambient air at 600 °C for 2 hours, and exhibit a specific surface area of 171.05 m² g⁻¹, and a higher quantity of functional groups (–NH₂ and oxygen). The morphological analysis demonstrates exfoliated nanosheets (average thickness ∼1.44 nm) with curly edges and fluffy structures. XPS analysis estimates the surface atomic ratio (C/N) as 0.988 and 0.758 for CN and CN-600, respectively, confirming lower structural flaws of the latter. CN-600 demonstrates a noteworthy improvement in its ability to degrade multiple pollutants and antibiotics in diverse aqueous solutions, showcasing its superior photocatalytic activity under solar radiation. CN-600 exhibits a higher rate constant than pristine CN by 3.66, 7.01, and 1.42 times, respectively, in the degradation of methylene blue, rhodamine B, and ciprofloxacin. This enhancement in photocatalytic performance is corroborated by a larger specific surface area of the nanosheets, an abundance of active sites, a higher number of functional groups (–NH₂ and oxygen), and a reduced distance of charge transfer between the layers. Overall, the g-C₃N₄ nanosheets exhibit significant potential as a high-performance photocatalytic material that operates efficiently with visible light, offering a plethora of possible applications in the fields of energy and the environment.