Graphitic carbon nitride nanosheets with low ON1-doping content as efficient photocatalysts for organic pollutant degradation

Abstract

Oxygen-doped (O-doped) graphitic carbon nitride (g-C₃N₄) usually presents excellent photocatalytic activity compared to pristine g-C₃N₄ with the common O_N2-doping. However, there are very few research studies concerned with the O_N1-doped g-C₃N₄. Herein, g-C₃N₄ nanosheet samples with two different O-doping positions (O_N1 and O_N2) were prepared and characterized. Different O_N1-doping contents were achieved via the polycondensation of g-C₃N₄ under different calcination temperatures for the precursor urea. Results showed that the as-prepared O_N1-doped g-C₃N₄ nanosheets with an oxygen content of 2.16% demonstrated the highest photocatalytic activity in degrading rhodamine B (RhB, 10 mg L⁻¹) with a degradation rate as high as 99% in 3 min under visible light irradiation, which is the best g-C₃N₄ photocatalyst compared to the literature reports for RhB degradation. The improved degradation was related to the decreased oxygen content of O_N1-doped g-C₃N₄ nanosheets instead of normal O_N2-doping, which was also confirmed by DFT computation.