Porous composite nanofibers consisted of cubic Bi 12 TiO 20, and orthorhombic Bi 4 Ti 3 O 12 with pore size of 5–10 nm have been successfully synthesized by combining electrospinning with calcination for photodegrading methyl orange (MO). Calcination temperature has a great effect on the ratio of Bi 12 TiO 20 and Bi 4 Ti 3 O 12 and their morphology, which in turn affects the photocatalytic property of the products. MO was almost completely degraded over the as-prepared samples obtained under the optimizing calcination temperature of 500 °C after irradiating for 40 min under simulated sunlight. Besides, cycle and regeneration experiments show that the porous Bi 12 TiO 20 /Bi 4 Ti 3 O 12 composite nanofibers possess fine cycle stability and regeneration ability, after the regenerative photocatalyst was recycled twice, 91% of the MO was degraded. Based on the characterization results, the mechanism of the improvement in photocatalytic property of Bi 12 TiO 20 /Bi 4 Ti 3 O 12 composite nanofibers was also investigated, and h + played a major role in the photodegradation of MO. In addition, the as-prepared Bi 12 TiO 20 /Bi 4 Ti 3 O 12 composite nanofibers show a certain capacity of photocatalytic hydrogen production under the simulated sunlight. This work not only provides a porous fiber with good photocatalytic activity, but also provides a reference for the preparation and performance study of other fibers.
Chun Du,Donghai Li,Qinyu He,Junming Liu,Wei Li,Guannan He,Yinzhen Wang
Hybrid Bi12TiO20/Bi4Ti3O12 composites with different Bi : Ti molar ratios were successfully fabricated using a one-step solid-state calcination. These samples were characterized using X-ray diffraction, specific surface area analysis, scanning electron microscopy, high-resolution microscopy, selected-area electron diffraction, X-ray photoelectron spectroscopy, UV-vis diffuse reflection spectroscopy, photoluminescence analyses, and photocurrent and electrochemical impedance spectroscopy. Some specified techniques were also used to investigate the photocatalytic properties and the formation of radical species under UV-vis irradiation. The composites provide an efficient pathway for photo-produced electrons and holes to diffuse and transfer to the exterior of the particles for photodegradation, because of the good contact between hybrid Bi12TiO20 and Bi4Ti3O12. Therefore, the hybrid Bi12TiO20/Bi4Ti3O12 can prolong the carrier lifetime as compared to any individual material (Bi12TiO20 or Bi4Ti3O12). In particular, the hybrid Bi12TiO20/Bi4Ti3O12 composite with a Bi : Ti ratio of 12 : 6 had the longest photo-generated carrier lifetime and produced the maximum amount of hydroxyl radicals during UV-vis irradiation; therefore, it demonstrated the best photo-catalytic properties. A Z-scheme mechanism was proposed to explain the hydroxyl radical yield and photodegradation.
Photocatalysis is recognized as one of the most promising techniques for environment purification. However, the inconvenient recovery of powder photocatalysts significantly impeded their practical applications. Immobilization of the photocatalysts on supports to form monolithic photocatalysts is an effective method to solve this problem. Herein, a monolithic photocatalyst Bi 12 TiO 20 /Bi 4 Ti 3 O 12 /SiOC is fabricated by growing optimal Bi 12 TiO 20 /Bi 4 Ti 3 O 12 S-scheme heterojunction onto 3D-printed porous SiOC support. On one side, S-scheme heterojunction facilitates the separation of photoinduced electrons and holes while retaining their strong redox ability. On the other side, the porous structure favors mass transport and improves light harvesting by reflecting the light several times. Under simulated solar light irradiation, the NO removal efficiency of the monolithic photocatalyst Bi 12 TiO 20 /Bi 4 Ti 3 O 12 /SiOC is 16.4 %. Furthermore, the composite has good stability and reusability, suggesting its great potential in practical application. The possible photocatalytic mechanism is proposed according to systematic experiments and density functional theory (DFT). This work provides a rational reference for constructing efficient photocatalysts for environmental purification.
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