Supramolecular precursor strategy for the synthesis of holey graphitic carbon nitride nanotubes with enhanced photocatalytic hydrogen evolution performance

A simple one-step thermal polymerization method was developed for synthesis of holey graphitic carbon nitride nanotubes, involving direct heating of mixtures of melamine and urea or melamine and cyanuric acid in specific mass ratios. Supramolecular structures formed between the precursor molecules guided nanotube formation. The porous and nanotubular structure of the nanotubes facilitated efficient charge carrier migration and separation, thereby enhancing photocatalytic H₂ production in 20 vol.% lactic acid under visible light irradiation. Nanotubes synthesized using melamine and urea in a 1:10 mass ratio (denoted herein as CN-MU nanotubes) exhibited a photocatalytic hydrogen production rate of 1, 073.6 μmol·h^-1·g^-1 with Pt as the cocatalyst, a rate of 4.7 and 3.1 times higher than traditional Pt/g-C₃N₄ photocatalysts prepared from graphitic carbon nitride (g-C₃N₄) obtained by direct thermal polymerization of melamine or urea, respectively. On the basis of their outstanding performance for photocatalytic H₂ production, it is envisaged that the holey g-C₃N₄ nanotubes will find widespread uptake in other areas, including photocatalytic CO₂ reduction, dye-sensitized solar cells and photoelectrochemical sensors.