Graphitic carbon nitride (g-C3N4) synthesis and heterostructures, principles, mechanisms, and recent advances: A critical review

Graphitic carbon nitride (g-C3N4) is a semiconductor polymeric photocatalyst with an attractive electronic band structure, a moderate band gap energy, facile synthesis, and functionalization which can be applied as a photocatalyst in the visible light of the spectrum. The main problem of the g-C3N4 photocatalyst is the recombination of the photo -generated electron-hole pairs. The photogenerated electrons in the conduction band (CB) tend to return to the valence band (VB) with subsequent recombination which is unfavored for photocatalysis. It is difficult for a single-component photocatalyst to harvest a large portion of the sunlight spectrum, and simultaneously, possess a suitable spatial charge separation and efficient redox ability. Constructing a heterojunction aims to satisfy the above three factors in a photocatalyst heterojunction system. Constructing g-C3N4-based heterostructures can promote electron-hole pair separation through the charge transfer across the interface of the g-C3N4/semiconductor. In this review, the photocatalysis mechanism is discussed and several types of g-C3N4/semiconductor heterostructuresincluding type II, Z-scheme, and S-scheme heterostructures are explained. Recent advances in different types of g-C3N4-based heterostructures have been addressed. The synthesis methods for mesoporous, 0D, 1D, and 3D g-C3N4 and different modifications on this photocatalyst are reviewed.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.