Construction of a Reduced Graphene Oxide/TiO₂ Nanotube Structure by the Click Reaction for Photoanodes

The combination of graphene with the traditional attractive photoanode material TiO2 has drawn much attention because of its charming ability in extending the light absorption range and enhancing the separation of photogenerated hole–electron pairs. However, achieving a stable and efficient combination between them is still challenging. Herein, a simple and effective method using the click chemistry reaction under mild conditions is proposed to functionalize two-dimensional (2D) reduced graphene oxide (rGO) onto highly ordered one-dimensional (1D) titanium dioxide nanotubes (TiO2 NTs). TiO2 NTs are first terminated with azide, while rGO is functionalized with alkynes. Then rGO can be tightly “clicked” onto the surface of TiO2 NTs by a one-step click reaction with Cu(I) as a catalyst at room temperature. The bonding process is studied by X-ray diffraction, Raman, infrared spectroscopy, and X-ray photoelectron spectroscopy. A potential growth mechanism has been proposed. The photoelectric properties of the resultant click-rGO/TiO2 NTs are compared with those of the ED-rGO/TiO2 NTs prepared by the traditional electrodeposition method. Results show that click-rGO/TiO2 NTs have a much higher visible light absorption performance, a faster charge transfer rate, and a greatly improved photocurrent response (about 3.3 times, under visible light irradiation) compared with ED-rGO/TiO2 NTs. It is speculated to be derived from the better interaction state and conjugated system that was created during the click reaction process between graphene and TiO2 NTs. The established method is indicated to be very suitable for a uniform, gentle, and efficient modification of 2D graphene on the surface of 1D nanotubes to serve as promising photoanodes.