Research progress for the controlled synthesis and photocatalytic performance of deep-coloredgraphitic carbon nitride

Graphitic carbon nitride (g-C₃N₄) is a highly concerned photocatalytic material, renowned for its excellenttability, suitable band gap, and favorable visible-light responsiveness. However, inherent drawbacks such as narrow visible-light absorption range, low specific surface area, and inefficient charge-carrier separation and transport significantly impede its practical use.Extensive research indicates that darkening the color of photocatalytic materials can effectively broaden their visible-light absorption spectrum, which not only enhances the utilization of light energy but also accelerates charge-carrier separation and transport efficiency. Conventionally synthesized g-C₃N₄ typically appears as a light-yellow powder. In contrast, strategies such as defect engineering, element doping, and morphology controlling can be employed to prepare dark-colored g-C₃N₄ powders. These strategies involve introducing defects like nitrogen or cyano defects into g-C₃N₄, doping with elements such as bromine or oxygen, or modifying the crystallinity and morphology of g-C₃N₄.This paper gives an overview ofthe advantages of dark-colored g-C₃N₄ and its recent progress. Subsequently, the preparation methods, structural characterization, photocatalytic performance, and applications for dark-colored g-C₃N₄were introduced.Finally, the development trends of future structural regulation strategies for dark g-C₃N₄, as well as the challenges it faces, such as the mechanism of color change and the contribution rate of light absorption performance, are summarized and prospected.