Template-free large-scale synthesis of g-C3N4 microtubes for enhanced visible light-driven photocatalytic H2 production

A template-free hydrothermal-assisted thermal polymerization method has been developed for the large-scale synthesis of one-dimensional (1D) graphitic carbonnitride (g-C3N4) microtubes. The g-C3N4 microtubes were obtained by simple thermal polymerization of melamine-cyanuric acid complex microrods under N2 atmosphere, which were synthesized by hydrothermal treatment of melamine solution at 180 °C for 24 h. The as-obtained g-C3N4microtubes exhibited a large surface area and a unique one-dimensional tubular structure, which provided abundant active sites for proton reduction and also facilitated the electron transfer processes. As such, the g-C3N4 microtubes showed enhanced photocatalytic H2 productionactivity in lactic acid aqueous solutions under visible light irradiation (λ ≥ 420 nm), which was ∼ 3.1 times higher than that of bulk g-C3N4 prepared by direct thermal polymerization of the melamine precursor under the same calcination conditions.