Carbon-Coated Graphitic Carbon Nitride Nanotubes for Supercapacitor Applications

A carbon-coated g-C3N4 nanotube (C-TCN) was constructed via the concurrent thermal polymerization of urea and carbonization of glucose. When the mass ratio of glucose to urea was 1/30, after the precursors were concurrently recrystallized from water, partially dried, and heated at 550 °C for 2 h, the carbon/g-C3N4 hybrid (TCN-200) with high nanotube content could be successfully prepared, the diameter of which was in the range of 45–80 nm. The formation mechanism of C-TCN was proposed as follows. As the cocrystal of urea and glucose could form a stacked layered structure because of hydrogen bonding, the newly formed carbon dots (CDots) originated from the carbonization of glucose might uniformly distribute on the surface of g-C3N4 layers that originated from the thermal polymerization of urea, and CDots could hinder the aggregation of g-C3N4 layers to form nanosheets like bulk g-C3N4 (BCN). With the increase of CDots, the adjacent CDots tended to interact and aggregate on the surface of g-C3N4 layers, which will drive the g-C3N4 layers to crimp and finally form nanotubular structures. With TCN-200 as the electrode material of the supercapacitor, its specific capacitance is ∼2 times that of BCN, owing to the synergistic advantages of highly conductive carbon and nanotubular structures. This facile one-step dual in situ method can afford a guidance for further studies of some TCN-based functional composites.