A BrO3–-modified Bi2O3/Bi(OH)3 heterojunction photocatalyst was in situ fabricated by a facile one-pot method and applied in photocatalytic nitrogen fixation. In comparison with Bi(OH)3, the Bi2O3/Bi(OH)3 heterojunction has a larger specific surface area from the nanoflower-like morphology and an extended visible light absorption range. Of special importance, the proper band gap match between Bi(OH)3 and Bi2O3, the multiple charge transfer channels via the BrO3– bridge, and the oriented electron migration in the type-II heterojunction mechanism make a stronger charge separation efficiency. Therefore, the BiO/BiHO-3 sample presented the highest photocatalytic nitrogen reduction performance with an ammonia production rate of 45.28 μmol g–1 h–1, which was 10 times higher than that of Bi(OH)3. Photogenerated cavities are consumed during H2O oxidation to produce O2 and H2O2. However, the O2 production was small, and the H2O2 yield was about 78.5 μmol g–1 h–1. For CO2 reduction, the CO production rate was 52.86 μmol g–1 h–1, which was 1.6 and 1.9 times those of Bi(OH)3 and Bi2O3. This work provides useful guidance for the design and synthesis of efficient catalysts for photocatalytic N2 fixation.
Chi Song,Lin-jie Wang,Si-miao Sun,Ying Wu,Li-jie XU,Lu Gan
A series of ternary composite photocatalysts of Bi 2 O 3 /Bi embedded in porous carbon (Bi 2 O 3 /Bi/PC) was prepared by the high-temperature pyrolysis of a bismuth-based metal organic framework (CAU-17(Bi)). They were used as photocatalysts for the degradation of organic Rhodamine B dye (RhB) in water under visible light. Results showed that the Bi 2 O 3 /Bi/PC composites with different Bi 2 O 3 /Bi ratios could be obtained through changing the extent of the carbothermal reduction of Bi 2 O 3 during pyrolysis. The photocatalystpyrolyzed at 800 o C showed the highest photocatalytic performance and had a wide applicable pH value range and excellent recyclability and stability.The components in the ternary composites exhibited a synergetic effect in the removal of RhB, where Bi 2 O 3 acted as a low-band gap semiconductor, metallic Bi transferred electrons generated by visible light excitation to the graphitic structure in porous carbon to inhibit the recombination of electrons with holes. The holes and peroxide radicals were the main active species. This study provides a new way for the design and preparation of visible-light active and high-performance photocatalysts for organic contaminant degradation in aqueous media by using metal organic frameworks as a multicomponent precursor.
Artificial Z-scheme photocatalytic systems, inspired by natural photosynthesis, have been widely employed for pollutant removal. In this study, we fabricated a ternary Z-scheme Bi 2 O 3 /Bi/porous carbon nitride (PCN) heterojunction with an intimately coupled interface through a simple EG-assisted solvothermal approach to improving photocatalytic performance of NO oxidation. The in-situ generated metallic Bi acts as an electron mediator, effectively accelerating the separation and transfer of photoexcited carriers. The unique Z-scheme charge transfer mechanism provides the strong redox abilities and isolates the active sites for specific reactions, thus promoting photocatalytic NO oxidation activity. As a result, the optimized Bi 2 O 3 /Bi/PCN sample achieved a NO removal efficiency of 94.6%, outperforming single-component catalysts and most previously reported heterojunction-based photocatalysts. Additionally, in-situ Fourier transform infrared spectroscopy was employed to propose the NO removal mechanism, offering valuable insight into the conversion pathway. Such a heterogeneous Z-scheme photocatalytic system with a strong redox ability, high charge-separation efficiency, and long-term stability, demonstrates significantly enhanced photoactivity for pollutant removal and is expected to attract increasing interest for other photocatalytic applications.
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