TiO-on-CN double-shell microtubes: In-situ fabricated heterostructures toward enhanced photocatalytic hydrogen evolution.

Structural design, doping, and construction of heterojunctions are effective strategies for producing highly efficient photocatalytic materials. Herein, N-doped TiO was formed on hexagonal CN tube through in-situ hydrolysis of a Ti source on a supramolecular precursor, followed by thermal treatment. As a result, a double-shell microtube, CN@TiO 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 TiO. The photocatalytic efficiency of CN@TiO was investigated by conducting hydrogen production experiments. The hydrogen production rate of CN@TiO was measured to be 10.1 mmol h g, which is 4 times and 15 times that of CN and TiO, respectively. The improved photocatalytic activity of CN@TiO 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 TiO 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.