Internal electric field in carbon nitride-based heterojunctions for photocatalysis

Carbon nitride is one of the most promising metal-free photocatalysts to harvest solar light for energy conversion and pollutant treatment. Unfortunately, its photocatalytic performance is impeded by the sluggish charge carriers due to the high symmetry of unit cells of chemical structure. Fabrication of an internal electric field (IEF) in carbon nitride-based photocatalysts is evidenced to be a productive strategy to actuate the fast separation of photo-excited charge carriers and navigate their migrations to active sites for high apparent quantum efficiency (AQE) and throughputs. In the current work, a comprehensive review of IEF in different types of carbon nitride-based heterojunctions will be well presented. Emphasis will be put on the latest progress of IEF generation by hosting 2-dimensional (2D) carbon nitride nanosheets with different dimensional materials, IEF modulation by interfacial engineering as well as IEF identification and monitoring. Relationships between IEF and photocatalytic performances in various processes will also be enlightened. Finally, this review will suggest the challenges and future perspectives of IEF-driven photocatalysis. This review brings the intrinsic impetus of charge carriers in a photocatalyst to the forefront and is anticipated to provide guidance to configure powered IEF in 2D carbon nitride-based heterostructures toward efficient energy conversion and environmental purification.