Graphitic carbon nitride based nanocomposites: a review

Abstract

Graphitic carbon nitride (g-C₃N₄), as an intriguing earth-abundant visible light photocatalyst, possesses a unique two-dimensional structure, excellent chemical stability and tunable electronic structure. Pure g-C₃N₄ suffers from rapid recombination of photo-generated electron–hole pairs resulting in low photocatalytic activity. Because of the unique electronic structure, the g-C₃N₄ could act as an eminent candidate for coupling with various functional materials to enhance the performance. According to the discrepancies in the photocatalytic mechanism and process, six primary systems of g-C₃N₄-based nanocomposites can be classified and summarized: namely, the g-C₃N₄ based metal-free heterojunction, the g-C₃N₄/single metal oxide (metal sulfide) heterojunction, g-C₃N₄/composite oxide, the g-C₃N₄/halide heterojunction, g-C₃N₄/noble metal heterostructures, and the g-C₃N₄ based complex system. Apart from the depiction of the fabrication methods, heterojunction structure and multifunctional application of the g-C₃N₄-based nanocomposites, we emphasize and elaborate on the underlying mechanisms in the photocatalytic activity enhancement of g-C₃N₄-based nanocomposites. The unique functions of the p–n junction (semiconductor/semiconductor heterostructures), the Schottky junction (metal/semiconductor heterostructures), the surface plasmon resonance (SPR) effect, photosensitization, superconductivity, etc. are utilized in the photocatalytic processes. Furthermore, the enhanced performance of g-C₃N₄-based nanocomposites has been widely employed in environmental and energetic applications such as photocatalytic degradation of pollutants, photocatalytic hydrogen generation, carbon dioxide reduction, disinfection, and supercapacitors. This critical review ends with a summary and some perspectives on the challenges and new directions in exploring g-C₃N₄-based advanced nanomaterials.