Photocatalytic properties of exposed crystal surface-controlled rutile TiO2 nanorod assembled microspheres

• TiO2 microspheres with rutile nanorods were fabricated.
• The exposed surface of nanorods could be controlled by adjusting NaCl concentration.
• Mechanism for the formation of TiO2 nanorods and microspheres was proposed.
• The TiO2 microspheres exhibited superior photocatalytic activity.

The photocatalytic activity of TiO2 is correlated with its exposed crystal surface, phase composition, morphology, and crystallite size. In this study, TiO2 microspheres with exposed crystal surface-controlled rutile TiO2 nanorods were fabricated by employing a simple hydrothermal reaction in the presence of NaCl solution. The crystal phase, morphology, and size of the as-obtained materials were significantly dependent on the NaCl concentration. The exposed crystal surface of TiO2 nanorods could be tailored by adjusting the NaCl concentration. With increasing NaCl concentration, the exposed area of the (1 1 1) crystal surface gradually decreased, whereas the area of the newly exposed (0 0 1) surface gradually increased. Characterization results indicated that the crystal phase of the TiO2 microspheres was the only rutile structure in the system and no brookite phase was found. The diameter of the microspheres can be changed from 3.5 μm to 2 μm by tuning the NaCl concentration. Photocatalytic degradation of papermaking wastewater using the synthesized materials showed that the photocatalytic activities of the samples are affected by the exposed (0 0 1) crystal surface of TiO2, which can induce the separation of electrons and holes, thereby resulting in improved photocatalytic activity.

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