Template-free synthesis of 2D porous ultrathin nonmetal-doped g-C3N4 nanosheets with highly efficient photocatalytic H2 evolution from water under visible light

• The 2D porous ultrathin O-doped g-C3N4 nanosheets was obtained by template-free method (the calcined method and chemical oxidation method at room temperature).
• The simultaneous modulations of the morphology, intrinsic electronic structure and band positions of the bulk g-C3N4 result in enhanced photocatalytic performance (photocatalytic H2 evolution and photocatalytic degradation of pollutants).
• By XPS VB, ESR analysis and so on, the photocatalytic mechanism was researched detailedly.

The novel two-dimensional (2D) porous ultrathin oxygen-doped g-C3N4 nanosheets (PUOCNs) were prepared. The comprehensive characterization methods were used to study morphology, microstructure, crystal structure, chemical states and photocatalytic performance of PUOCNs. 2D porous ultrathin structure and the introduction of oxygen are beneficial to the enhancement of the photocatalytic activity of PUOCNs. The average H2 evolution rate of PUOCNs is ∼189.3 μmol h−1, which is ∼5.2 times higher than that of the bulk g-C3N4 and the degradation efficiency of organic dye methyl orange (MO) is almost 71 times higher than that of the bulk g-C3N4. The enhanced photocatalytic activity is due to the more adsorption sites and more active sites, the enhanced redox ability and improved electron transport ability, which leads to less recombination and a more efficient separation of photogenerated electron and hole pairs. Through XPS VB and ESR analysis, the photocatalytic mechanism was also researched in detail.

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