Preparation of the TiO₂/Graphic Carbon Nitride Core-Shell Array as a Photoanode for Efficient Photoelectrochemical Water Splitting

The photoelectrochemical (PEC) oxygen evolution reaction over a photoanode is a promising process for renewable energy. The fascinating properties of graphic carbon nitride (g-CN) in water splitting make the photoelectrode engineering of it for PEC use quite meaningful. In this work, we report the fabrication of the core-shell-structured TiO₂/g-CN composite film by hydrothermal growth for TiO₂ nanorod arrays and solvothermal growth for the g-CN layer. Herein, TiO₂ is used as an effective electron-transfer layer, and g-CN is used as a visible light absorption layer. Different reaction conditions were investigated in order to obtain the uniform TiO₂/g-CN nanorod core-shell structure. Outstanding photoelectrochemical performances of the optimized composites were obtained compared to that of pristine TiO₂ or g-CN because the high-quality heterojunction between g-CN and TiO₂ turned out to effectively reduce the recombination of charge carriers and improve the photoelectric conversion ability. Thus, the photocurrent density under visible light of TiO₂/g-CN reached 80.9 μA cm^-2, which is 21 times that of g-CN under 0.6 V (vs SCE). Finally, a systematic photoelectrocatalytic mechanism of charge carrier migration and the recombination path in the TiO₂/g-CN nanorod core-shell heterojunction was proposed, which can be considered to be a probable explanation of efficient PEC performance.