Scalable and clean exfoliation of graphitic carbon nitride in NaClO solution: enriched surface active sites for enhanced photocatalytic H2 evolution

Graphitic carbon nitride (g-C3N4) has attracted wide attention as a promising visible-light-driven metal-free semiconductor photocatalyst. The transportation and transformation of photogenerated carriers during the photocatalytic process of g-C3N4 are restricted by the insufficient surface active sites and low charge separation efficiency. As a top-down strategy, the exfoliation of layer-stacked bulk g-C3N4 into nanosheets is widely recognized as an applicable route, yet still challenging in terms of scalable and clean synthesis. Herein, this challenge was tackled via a simple hydrothermal method in NaClO solution, in which the synergetic effect of alkaline metal ion intercalation and the oxidative exfoliation of bulk g-C3N4 was involved. Highly active g-C3N4 nanosheets were easily made in the laboratory in tens of grams and this simple process could readily be extended to the scale of kilograms. The hydrothermal treatment created vertical channels for directional electron transfer and obtained ultrathin holey g-C3N4 nanosheets with remarkable hierarchical porosity and good hydrophilicity. The holey g-C3N4 nanosheets exhibit a high specific surface area (170.7 m(2) g(-1)), a narrow band gap (2.55 eV), a large number of exposed edges, and superior electron transport ability. These holey g-C3N4 nanosheets have an average H-2 evolution rate 9 times that of bulk g-C3N4. This green, facile and scalable method to synthesize few-layer g-C3N4 nanosheets affords a new strategy to design and fabricate other functional 2D materials.