Zhiqiao He,Yuanqiao Shi,Chao Gao,Lina Wen,Jianmeng Chen,Shuang Song
A novel visible-light-active BiOCl/BiVO4 photocatalyst with a p–n heterojunction structure was prepared using a hydrothermal method. The photocatalytic activity of the heterojunction was investigated by monitoring the change in methyl orange (MO) concentration under visible-light irradiation. The results reveal that the composite exhibited markedly improved efficiency for MO photodegradation in comparison with pure BiVO4, BiOCl, and Degussa P25. This is ascribed to the B-type heterojunction structure with a strong oxidative ability and efficient charge separation and transfer across the BiOCl/BiVO4 p–n junction. The highest activity was obtained in the BiOCl/BiVO4 heterojunction using a composite of 13 mol % BiOCl and 87 mol % BiVO4. The removal of MO was mainly initiated by valence-band holes, but dissolved oxygen also played a crucial role in consuming the conduction-band electrons. This was verified by the effects of scavengers and N2 purging.
Herein, Fe 3 O 4 quantum dots modified BiOCl/BiVO 4 p-n heterojunction was successfully synthesized by a facile strategy. Multiple techniques were carried out to characterize the as-prepared samples. Results show that the photocatalysts possess regular crystal structure and consisted of BiOCl/BiVO 4 nanosheet structure with Fe 3 O 4 QDs on its surface. Particularly, 20% Fe 3 O 4 QDs@BiOCl/BiVO 4 p-n heterojunction shows universal outstanding photocatalytic activity for removing four different broad-spectrum antibiotics under visible light. Meanwhile, the mineralization degree and degradation pathways of antibiotic were further studied by 3D-EEMs and LC-MS/MS. The improved photocatalytic performance for degradation of broad-spectrum antibiotics mainly attributes to the effective charge carrier mobility, large specific surface areas, and strong visible light absorption. The photocatalytic reaction mechanism was also revealed by the electron spin resonance (ESR) technique and the active species trapping experiments. The photocatalyst stays stable crystal structures after four reaction cycles and it can be easily separated from the solution by an external magnetic field both demonstrate that the Fe 3 O 4 QDs@BiOCl/BiVO 4 p-n heterojunction has unlimited potential for practical usage. This work is expected to be widely applicable to the removal of broad-spectrum antibiotics.
Graphical Photocatalysis : The sandwiched Bi 2 S 3 −BiOCl/BiVO 4 composites were fabricated and exhibited better photocatalytic performance than single BiVO 4 and binary Bi 2 S 3 /BiVO 4 composites due to the accelerated photogenerated charge transfer and separation, abundant exposed active sites, and enhanced visible light absorption. The development of cost-efficient and feasible strategies for producing efficient photocatalysts is crucial to advance photocatalytic pollutants degradation. Herein, we report a high photocatalytic active hierarchical sandwiched Bi 2 S 3 −BiOCl nanoarrays/BiVO 4 nanosheets composites fabricated using biomass-derived BiVO 4 porous nanosheets as starting substrate material. BiVO 4 porous nanosheets were first prepared via an impregnation-calcination process using biomass template method. Subsequently, the ion exchange reactions during solvothermal reaction realized the in situ nucleation and growth of Bi 2 S 3 nanorods and BiOCl nanoflakes nanoarrays from both sides of BiVO 4 porous nanosheets, resulting in the formation of hierarchical sandwiched Bi 2 S 3 −BiOCl nanoarrays/BiVO 4 nanosheets composites. Specifically, well-defined Bi 2 S 3 nanorods and BiOCl nanoflakes nanoarrays are vertically grown on the surface of BiVO 4 nanosheets to provide plenty of accessible active sites and enable visible light harvesting. The tight contact between different components promises fast electron transfer and excellent durability. Consequently, optimized sandwiched Bi 2 S 3 −BiOCl/BiVO 4 composite exhibits superior photocatalytic activity for pollutants degradation.
Lulu Zhu,Baiyu Zhang,Qian Su,Runlu Liu,Jingyi Lin,Hua Wang,Shenmin Zhu,Yao Li
Photoinduced charge separation and surface reactions are essential for ensuring high quantum efficiency of the photochemical and photophysical processes. BiVO4-based heterojunctions are promising materials for high-performance photocatalysts; however, their photocatalytic performance is significantly lower than the theoretical limit due to the sluggish water oxidation dynamics and rapid recombination of charge carriers on the catalyst surface. To address these issues, oxygen vacancies (OVs) are introduced to a rationally designed BiVO4-based heterojunction using built-in potential and gradient OVs to promote the separation of carriers and increase the photocatalytic activity. The heterojunctions with OVs exhibit a 2-fold increase in the photocatalytic activity for phenol degradation compared with that of pristine BiVO4. Additionally, density functional theory is applied to elucidate the synergistic mechanism of light absorption and charge separation in BiOCl/BiVO4 p–n heterojunction photocatalysts containing vacancies. The obtained results demonstrate a synergistic effect of vacancies and the built-in potential, providing a pathway for defect engineering in photocatalytic processes.
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