TiO₂-on-C₃N₄ double-shell microtubes: In-situ fabricated heterostructures toward enhanced photocatalytic hydrogen...

Structural design, doping, and construction of heterojunctions are effective strategies for producing highly efficient photocatalytic materials. Herein, N-doped TiO₂ was formed on hexagonal C₃N₄ tube through in-situ hydrolysis of a Ti source on a supramolecular precursor, followed by thermal treatment. As a result, a double-shell microtube, C₃N₄@TiO₂ heterostructure was fabricated. It was worth noting that the supramolecular precursor was prepared from melamine and cyanuric acid, which not only served as a template for the double-shell tubular structure, but also provided nitrogen for the doping of TiO₂. The photocatalytic efficiency of C₃N₄@TiO₂ was investigated by conducting hydrogen production experiments. The hydrogen production rate of C₃N₄@TiO₂ was measured to be 10.1 mmol h^-1 g^-1, which is 4 times and 15 times that of C₃N₄ and TiO₂, respectively. The improved photocatalytic activity of C₃N₄@TiO₂ can be ascribed to (1) the tubular structure that provides a large number of reaction sites and enhances mass transport, (2) the heterojunction that is beneficial to charge separation, and (3) doping of TiO₂ with nitrogen which extends its optical absorption range to visible light. This work demonstrates a facile method for synthesizing a highly efficient photocatalyst towards hydrogen evolution by modifying its structure and chemical composition as well as forming a heterojunction.