**4. Advantages of g-C3N4 materials in photocatalyst**

The advantages of photocatalysts with varied morphologies are obvious. Twodimensional photocatalysts made in a specific way, for example, have a bigger specific surface area and more reactive sites. Other decorative components introduced throughout the construction process can also be used. However, there are still certain issues, such as a tight reaction temperature requirement and uneven particle distribution.

#### **4.1 Doping of elements**

The use of element doping to change the band structure of photocatalysts and enlarge the light absorption zone is an effective method [9]. Non-metallic (B, O, S, I) doped g-C3N4 has been widely utilized to alter the optical absorption of internal bandgap structure and to adjust the photocatalytic performance of g-C3N4 to promote the redox potential in visible light [10–14]. The light absorption range of nanosheets, on the other hand, reduces due to the quantum confinement effect, which increases the band

gap [15, 16]. As a result, we can apply elemental doping to change the band structure of g-C3N4, which improves both light absorption and charge separation [17]. Oxygen doping, boron doping, phosphorus doping, and halogen doping will all be investigated.
