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

Graphitic carbon nitride (g-C 3 N 4) 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-C 3 N 4 photocatalyst is the recombination of the photogenerated 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–C 3 N 4 –based heterostructures can promote electron-hole pair separation through the charge transfer across the interface of the g-C 3 N 4 /semiconductor. In this review, the photocatalysis mechanism is discussed and several types of g-C 3 N 4 /semiconductor heterostructures including type II, Z-scheme, and S-scheme heterostructures are explained. Recent advances in different types of g–C 3 N 4 –based heterostructures have been addressed. The synthesis methods for mesoporous, 0D, 1D, and 3D g–C 3 N 4 and different modifications on this photocatalyst are reviewed. [Display omitted] • g-C 3 N 4 heterostructures are designed to improve charge carrier separation. • g-C 3 N 4 heterostructures increase the life time of electron and hole. • Type II, Z-scheme, and S-scheme heterostructures show different charge carrier path. • S-scheme heterojunctions are able to preserve the powerful photogenerated electrons and holes. • g-C 3 N 4 heterostructures improve the photocatalytic performance in pollutant degradation or H 2 production. [ABSTRACT FROM AUTHOR]