- Preparation and Photoconductivity of Films of Bi2O3-MO3 (M equals Mo, or W) Obtained by Rapid Quenching.
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The Bi//2O//3-MO//3 films (M equals Mo or W) were prepared by a rapid quenching technique using a twin-roller type equipment. The quenched films containing from 2. 5 to 5 mol% MO//3 or WO//3 precipitated only a tetragonal phase. By further increase of these oxide additives, a cubic phase ( delta -phase) was formed coexisting with the tetragonal one. The lowest content of the additives to form singly the delta -phase was 12. 5% for MoO//3// and 10% for WO//3 respectively. The quenched films were characterized by a high photoconductivity. The highest photoconductivity appeared when a beam of about 500 nm in wavelength was irradiated on the film. The photoconduction was observed in all films containing less than 12. 5% additives.
- Sekiya,Tsuzuki,Torii
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- Hydrothermal synthesis of Ca3Bi8O15 rods and their visible light photocatalytic properties
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High efficient visible light Ca3Bi8O15 photocatalysts were synthesized by a hydrothermal method. Characterized by X-ray diffractometer, transmission electron microscopy, and the UV-vis diffuse reflectance spectroscopy, the results showed that the novel Ca 3Bi8O15 rods can utilize the sunlight efficiently with the small band-gap. Using methyl orange (MO) as a model organic pollutant, the photocatalysts exhibited good photocatalytic activity, with the photodegradation conversion ratio of MO being up to 90% after 2 h of visible light (420 nm 2·- and OH.
- Li, Wenjuan,Kong, Desheng,Cui, Xiaoli,Du, Dandan,Yan, Tingjiang,You, Jinmao
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- Monoclinic dibismuth tetraoxide (m-Bi2O4) for piezocatalysis: new use for neglected materials
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Piezocatalysis is a promising approach for environmental pollutant removal. Monoclinic dibismuth tetraoxide (m-Bi2O4) was first applied to piezocatalyze organics under ultrasonic vibration. The built-in electric field with ultrasonic stress drives the separation of holes and electrons inm-Bi2O4. Its excellent piezocatalytic activity, reusability and chemical stability makem-Bi2O4a new candidate of piezocatalysis.
- Liu, Fengling,Chen, Haoxuan,Xu, Chenmin,Wang, Linlin,Qiu, Pengxiang,Gao, Shuo,Zhu, Jiawei,Zhang, Shuai,Guo, Zhaobing
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- B4O7, the first defined binary bismuth(III,V) oxide
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The thermal decomposition of both amorphous and crystalline bismuth (III, V) oxide hydrates has been investigated by applying a high oxygen pressure p02 up to 400 MPa, and the products were characterized by X-ray powder techniques. Two of the obtained pure bismuth(III, V) oxide phases derive from the CaF2-type structure with the unit cell dimensions a = 553.90(5) pm and a = 547.54(3) pm. The X-ray diffraction studies do not indicate any significant homogeneity range with respect to the oxygen content. Bi4O7, which is reported for the first time, only forms at high oxygen pressures. The X-ray powder diffraction diagram indicates a triclinic pyrochlore structure.
- Begemann,Jansen
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- Ag0/Au0nanocluster loaded Bi2O4photocatalyst for methyl orange dye photodegradation
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Visible-light-sensitive Ag and Au nanocluster loaded Bi2O4(Ag-Bi2O4and Au-Bi2O4) semiconductor photocatalysts have been synthesized. The composite materials exhibited increased photocatalytic degradation of the azo-dye pollutant, Methyl Orange (MO). In addition, Au-Bi2O4(Au-7% wt) showed the highest MO degradation rate (0.05904 min?1)i.e.7.69 times higher than the pristine Bi2O4and 1.4 times higher than 1% Ag-Bi2O4. The optical properties of the composites showed that the band gaps of the composite samples 1% Ag-Bi2O4and 7% Au-Bi2O4were 1.96 eV and 2.09 eV, respectively. The increase in the degradation rate is attributed to the decrease of the recombination rate of photoinduced e?/h+, caused by the enhanced charge transfer between the metal nanoparticles and Bi2O4as confirmed in the photocurrent measurements. The photocurrent measurements showed increase in the transients output by 8.25 times and 2.75 times for 1% Ag-Bi2O4& 3% Au-Bi2O4, respectively as compared to that of the pristine Bi2O4. These features further aided the increase in the photocatalytic efficiency while retaining the original physical properties, thus showing the robustness of Bi2O4as a photocatalyst.
- Bae, Jong-Seong,Dalayoan, Daryll J. C.,Hasan, Najmul,Kim, Jongseo,Lee, Jaehyun,Lee, Jongmin,Liu, Chunli
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- Preparation of bismuth oxides with mixed valence from hydrated sodium bismuth oxide
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Hydrothermal treatment up to 200°C of the hydrated sodium bismuth oxide, NaBiO3·nH2O, resulted in the formation of some bismuth oxides. The major phase is α-Bi2O3 above 190°C, a bismuth oxide with mixed valence around 160°C and monoclinic Bi2O4 around 140°C. Monoclinic Bi2O4 is a new bismuth oxide with mixed valence, Bi3+Bi5+O4, isostructural with β-Sb2O4. Its lattice parameters are a = 12.2668(2), b = 5.1180(1), c = 5.5670(1)angstrom and β = 107.838(1)° in the monoclinic system. Both bismuth oxides containing Bi5+ change to α-Bi2O3 on heating in air at 600°C, accompanied by weight loss caused by reduction of Bi5+ to Bi3+, monoclinic Bi2O4 via an intermediate phase during the course of pyrolysis.
- Kinomura, Nobukazu,Kumada, Nobuhiro
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- Fabrication of Z-scheme MoO3/Bi2O4 heterojunction photocatalyst with enhanced photocatalytic performance under visible light irradiation
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Constructing Z-scheme heterojunction to improve the separation efficiency of photogenerated carriers of photocatalysts has gained extensive attention. In this work, we fabricated a novel Z-scheme MoO3/Bi2O4 heterojunction photocatalyst by a hydrothermal method. XPS analysis results indicated that strong interaction between MoO3 and Bi2O4 is generated, which contributes to charge transfer and separation of the photogenerated carriers. This was confirmed by photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) tests. The photocatalytic performance of the as-synthesized photocatalysts was evaluated by degrading rhodamine B (RhB) in aqueous solution under visible light irradiation, showing that 15% MoO3/Bi2O4 (15-MB) composite exhibited the highest photocatalytic activity, which is 2 times higher than that of Bi2O4. Besides, the heterojunction photocatalyst can keep good photocatalytic activity and stability after five recycles. Trapping experiments demonstrated that the dominant active radicals in photocatalytic reactions are superoxide radical (?O2?) and holes (h+), indicating that the 15-MB composite is a Z-scheme photocatalyst. Finally, the mechanism of the Z-scheme MoO3/Bi2O4 composite for photo-degrading RhB in aqueous solution is proposed. This work provides a promising strategy for designing Bi-based Z-scheme heterojunction photocatalysts for highly efficient removal of environmental pollutants.
- Jiang, Tiangui,Wang, Kai,Guo, Ting,Wu, Xiaoyong,Zhang, Gaoke
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- Preparation and crystal structure of a new lithium bismuth oxide: LiBiO3
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A new lithium bismuth oxide was discovered during the investigation of low-temperature hydrothermal reactions of the hydrated sodium bismuth oxide, NaBiO3 · nH2O. This lithium bismuth oxide crystallizes in the orthorhombic system with the lattice parameters a = 8.8278(3), b = 4.9135(2), and c = 10.6914(3) A, space group Pccn, and Z = 8. The crystal structure was refined using neutron powder diffraction data giving final R factors of RWP= 10.04, RP = 7.64, RE = 3.88, and RI = 4.86%. The LiBiO3 crystal structure is similar to that of LiSbO3. Both structures can be considered as based on an array of hexagonally closed packed oxygen atoms with cations occupying two-thirds of the octahedral sites. In both structures, the LiO6 octahedra share faces to form a continuous string. However, in the LiSbO3 structure SbO6 octahedra each share two edges forming a continuous zigzag chain whereas in the LiBiO3 structure BiO6 octahedra each share one edge only. Thus, the LiBiO3 structure also resembles the cubic KBiO3 structure, both structures being based on a dimer unit of the type Bi2O10 which shares corners forming a network having interstitial alkali cations. On heating to about 300°C, LiBiO3 transforms to LiBiO2 through evolution of oxygen and reduction of Bi5+ to Bi3+.
- Kumada,Takahashi,Kinomura,Sleight
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- The boosted photocatalytic activity over perylene diimide modified Bi2O4 hybrid photocatalyst with internal electric field
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In this paper, an organic-inorganic perylene diimide modified Bi2O4 (PDI/Bi2O4) composite photocatalyst was successfully prepared. Its apparent morphology, chemical structure, element composition and chemical state were measured through XRD, XPS, TEM and DRS. It is observed that because of formed an internal electric field, PDI nanorods are well attached to the surface of Bi2O4 nanorods, and a compact interfacial contact is formed, which greatly accelerates the migration rate of photogenerated carriers. When the PDI/Bi2O4 composite photocatalyst was used to degrade Rhodamine B, the reaction rate was 0.169 min-1, which was 7.3 folds more than Bi2O4, and could maintain 80% after three times recycling experiments. Then, combined with the electronic band structure of PDI and Bi2O4, type Ⅱ photocatalytic mechanism is speculated.
- Zhang, Xiaoli,Shi, Lei,Yao, Lizhu,Cui, Lishuang
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