Sulfur-Mediated Self-Templating Synthesis of Tapered C-PAN/g-C₃N₄ Composite Nanotubes toward Efficient Photocatalytic H₂ Evolution

Hollow one-dimensional (1-D) nanostructures have drawn great attention in heterogeneous photocatalysis. Herein, we report that tapered polyacrylonitrile-derived carbon (C-PAN)/g-C₃N₄ composite nanotubes can be synthesized through a facile sulfur-mediated self-templating method via thermal condensation of polyacrylonitrile (PAN), melamine, and sulfur. The hollow tapered C-PAN/g-C₃N₄ composite nanotubes exhibit superior photocatalytic H₂ evolution performance under visible light irradiation. The 5 wt % C-PAN/g-C₃N₄ composite nanotubes show a 16.7 times higher photocatalytic H₂ evolution rate than that of pure g-C₃N₄, which is even 4.7 times higher than that of a 5 wt % C-PAN/g-C₃N₄ nanosheet composite obtained without sulfur. The hollow nanotubular composite structure provides g-C₃N₄ with higher specific surface area, enhanced light absorption, and better charge carrier separation and transfer, which synergistically contribute to the superior photocatalytic activity. Our work provides a new strategy to develop carbon-based architected photocatalysts.