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

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.