g-C₃N₄-based 2D/2D composite heterojunction photocatalyst

Employing semiconductor photocatalysis to transform solar energy into chemical energy provides a practicable strategy for the alleviation of energy and environmental crisis. Graphitic carbon nitride (g-C₃N₄) is a popular 2D photocatalyst with numerous advantages, such as visible light response, low cost, and high stability. However, single g-C₃N₄ photocatalyst displays poor performance due to fast recombination of photogenerated electrons and holes. To improve this limitation, many research works have focused on the construction of g-C₃N₄-based 2D/2D heterojunction photocatalysts by hybridizing g-C₃N₄ with other 2D materials. The intimate face-to-face contact in 2D/2D heterojunction offers large contact area and plentiful channels for the migration and separation of photogenerated charge carriers. Furthermore, 2D/2D heterojunction inherits the strengths of 2D structure, including high specific surface area, abundant adsorption sites and active sites. Herein, the preparation, mechanism, and application of g-C₃N₄-based 2D/2D heterojunction photocatalysts are reviewed. Three common preparation methods are summarized, including solid phase reaction, in situ growth, and electrostatic self-assembly. Various photocatalytic mechanisms are discussed, including traditional type-II, Z-scheme and S-scheme mechanisms. A series of applications in energy and environment fields are illustrated. Finally, future directions for the development of g-C₃N₄-based 2D/2D heterojunction photocatalysts are proposed. Copyright © 2021 Wiley-VCH GmbH.