Template-Free Synthesis of Phosphorus-Doped g-C₃N₄ Micro-Tubes with Hierarchical Core–Shell Structure for High-Efficient Visible Light Responsive Catalysis

This work reports a new form of tubular g-C₃N₄ that is featured with a hierarchical core–shell structure introduced with phosphorous elements and nitrogen vacancies. The core is self-arranged with randomly stacked g-C₃N₄ ultra-thin nanosheets along the axial direction. This unique structure significantly benefits electron/hole separation and visible-light harvesting. A superior performance for the photodegradation of rhodamine B and tetracycline hydrochloride is demonstrated under low intensity visible light. This photocatalyst also exhibits an excellent hydrogen evolution rate (3631 µmol h⁻¹g⁻¹) under visible light. Realizing this structure just requires the introduction of phytic acid into the solution of melamine and urea during hydrothermal treatment. In this complex system, phytic acid plays as the electron donor to stabilize melamine/cyanuric acid precursor via coordination interaction. Calcination at 550 °C directly renders the transformation of precursor into such hierarchical structure. This process is facile and shows the strong potential toward mass production for real applications.