Graphene-like graphitic carbon nitride (g-C3N4) as a semiconductor photocatalyst: Properties, classification, and defects engineering approaches

Graphitic carbon nitride (g-C3N4) is a promising polymeric semiconductor comprised of carbon and nitrogen, both of which have natural abundance, making it an attractive and affordable candidate to drive light-induced catalysis and chemical conversions. Recently, much attention has been devoted to tailor functional features of g-C3N4 for using them in photocatalytic applications, particularly photocatalyzed hydrogen (H2) evolution reaction and pollution control by catalyzing and thus eliminating toxic pollutants. It enabled us to systematically review significant advancements made to exploit the application of graphitic carbon nitride (g-C3N4) as a promising semiconductor photocatalyst. This paper presents a systematic overview of various forms of graphitic carbon nitride including bulk, mesoporous, exfoliated to ultrathin sheets and nanostructured variants, highlighting each form's distinct properties and advantages. Furthermore, the intrinsic properties of these structures have been thoroughly discussed, including metal-free composition, crystal structure, optical properties, and thermal stability. Moreover, a comprehensive survey of various synthesis pathways, including poly-addition and poly-condensation methods using different precursors, is provided. In addition, the mechanism of photocatalysis as well as barriers and limitations to efficient photocatalytic performance, primarily due to rapid charge recombination, are being addressed. This review also underscores the significance of co-catalyst loading in augmenting the photocatalytic performance of pristine g-C3N4 materials. By conducting an exhaustive examination of these aspects, the research underscores the enormous promise of g- C3N4 in transforming the realm of renewable energy generation and ecological sustainability.