General self-fission strategy via supramolecular self-assembly for high-yield and cost-effective synthesis of g-C₃N₄...

Graphitic carbon nitride (g-C₃N₄) is one of the most promising candidates as a photocatalyst. However, the practical application of g-C₃N₄ has been hindered by its high-cost, low-yield synthesis methods. Herein, we develop a high-yield, cost-effective synthesis strategy for fabricating g-C₃N₄ nanostructures by low-temperature (430 °C) air pre-etching, which can induce the self-fission of supramolecular precursors (SMPs). This new synthesis strategy can achieve a production yield of ∼35 wt% and ∼41 wt% for g-C₃N₄ nanosheets (CNs) and sulfur-doped g-C₃N₄ nanotubes (SCNt), notably higher than the yields of conventional methods (<10 wt%). The underlying mechanism for the higher production yield is that this low-temperature etching method can effectively slow down the decomposition rate of SMPs and in this way promote their polymerization into g-C₃N₄. The pre-etching method can significantly increase the specific surface areas of the obtained sample, resulting in higher BET values of CNs (132.7 m² g^-1) and SCNt (112.9 m² g^-1), which are 2.5 and 3.2 times those for the samples without pre-etching treatment. Moreover, the as-prepared nanostructures exhibit remarkable photocatalytic performance, with hydrogen production rates of 1464.2 and 2883.4 micromol h^-1 g^-1 for CNs and SCNt, respectively, achieving 10.2- and 20.1-fold enhancements over bulk g-C₃N₄. In addition, the successful synthesis of nanosheets from 2,4,6-triaminopyrimidine-cyanuric acid and commercially available melamine-cyanurate precursors further demonstrates the broad applicability of this strategy. Notably, the successful synthesis of 70 g of CNs confirms that the proposed strategy is capable of large-scale production of novel photocatalysts. This scalable and economical strategy lays a solid foundation for future industrial applications of g-C₃N₄-based photocatalysts.