Study on surface modification of g-C3N4 photocatalyst

g-C3N4 powders with different morphology and surface charged property were obtained by acidification, oxidation and exfoliation treatment of melamine. Acid treatment converts -NH2 group in melamine into -NH3NO3 group, and further oxidation reduces the existing CNH bond, promotes the formation of CNC and N(C)3 bond in gC3N4, and ensures the formation of layered g-C3N4 structure; acid treatment and exfoliation were beneficial to increase the pore volume of g-C3N4 and enhance the redox ability of g-C3N4. The degradation rate of acid treated g-C3N4 to Rhodamine B in visible light was 3.13 times that of untreated g-C3N4, and the degradation rate of acid treated g-C3N4 to ciprofloxacin was 5.04 times that of untreated g-C3N4, further indicating that acid treated-oxidation-exfoliated treatment can improve the photocatalytic degradation effect of g-C3N4 and expand the application range of g-C3N4. The layered g-C3N4 with different surface charges can be selectively loaded onto the semiconductor materials with exposed active crystal surfaces, providing conditions for controllable preparation of Z-type heterojunction with enhanced redox ability. •g-C3N4 powders with different redox ability and surface charges was prepared.•Acid treatment promotes the formation of CNC and N-(C)3 bonds in g-C3N4.•Acid-oxidation-exfoliation can improve the photocatalytic degradation of g-C3N4.