Advancing Graphitic Carbon Nitride-Based Photocatalysts toward Broadband Solar Energy Harvesting

In recent years, increasing efforts have been devoted to widening the light response range of graphitic carbon nitride (g-C3N4) for photocatalytic environmental remediation and fuel production. To delineate the state-of-the-art and suggest future directions, we critically assess the recent reports on the design of broadband g-C3N4 based photocatalysts for harvesting photons from ultraviolet to visible, and further to near-infrared (NIR). In this Review, we first introduce the fundamentals of g-C3N4, including molecular structure, electronic structure, and synthesis methods. We then discuss the strategies adopted to extend the optical absorption of g-C3N4 toward longer wavelengths, with a particular emphasis on the use of plasmonic and upconversion materials, as well as on its coupling with narrow-bandgap semiconductors to construct heterojunctions. We then summarize the photocatalytic systems using the three major strategies for photocatalytic applications, especially for NIR photocatalysis. We also point out the limitations of each strategy and potential solutions. Finally, we discuss the challenges in this dynamic research field and provide perspectives for future research. This Review may offer guidance for the rational design of g-C3N4-based photocatalysts for broadband solar photon harvesting.