- Synthesis of Bi2O3 architectures in DMF-H 2O solution by precipitation method and their photocatalytic activity
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Well-crystalline flowerlike α-Bi2O3 hierarchical architectures with pineapple-shaped petals have been synthesized by precipitation method at a volume ratio of DMF/H2O of 5, where DMF and H2O were used to dissolve Bi(NO3)3 and KOH, respectively. If the DMF/H2O ratio was decreased to 2:1, 1:1 and 0:30, flower-, bundle- and dendrite-shaped α-Bi2O3 microcrystallites aggregated by nanorods were formed, respectively. The simple synthetic route and thus obtained Bi2O3 architectures of various morphologies provide a basis insight for their formation mechanism. The photocatalytic activity of the as-prepared Bi2O3 particles for degradation of Rhodamine B (RhB) under visible-light irradiation was obviously influenced by their morphologies. Bi2O3 of nanorod-based microstructures exhibited higher photodegradation activity than nanobrick-based ones, owing to higher light absorption and carrier separation efficiency in one-dimensional (1D) nanostructured materials.
- Yang, Li-Li,Han, Qiao-Feng,Zhao, Jin,Zhu, Jun-Wu,Wang, Xin,Ma, Wei-Hua
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- Surface Modifications of (ZnSe)0.5(CuGa2.5Se4.25)0.5to Promote Photocatalytic Z-Scheme Overall Water Splitting
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Charge separation is crucial for an efficient artificial photosynthetic process, especially for narrow-bandgap metal sulfides/selenides. The present study demonstrates the application of a p-n junction to particulate metal selenides to enhance photocatalytic Z-scheme overall water splitting (OWS). The constructed p-n junction of CdS-(ZnSe)0.5(CuGa2.5Se4.25)0.5 significantly boosted charge separation. A thin TiO2 coating layer also was introduced to inhibit photocorrosion of CdS and suppress the backward reaction of water formation from hydrogen and oxygen. By employing Pt-loaded TiO2/CdS-(ZnSe)0.5(CuGa2.5Se4.25)0.5 as a hydrogen evolution photocatalyst (HEP), we assembled a Z-scheme OWS system, together with BiVO4:Mo and Au as an oxygen evolution photocatalyst and electron mediator, respectively. An apparent quantum yield of 1.5% at 420 nm was achieved, which is by far the highest among reported particulate photocatalytic Z-scheme OWS systems with metal sulfides/selenides as HEPs. The present work demonstrates that a well-tailored p-n junction structure is effective for promoting charge separation in photocatalysis and opens new pathways for the development of efficient artificial photosynthesis systems involving narrow bandgap photocatalysts.
- Chen, Shanshan,Vequizo, Junie Jhon M.,Pan, Zhenhua,Hisatomi, Takashi,Nakabayashi, Mamiko,Lin, Lihua,Wang, Zheng,Kato, Kosaku,Yamakata, Akira,Shibata, Naoya,Takata, Tsuyoshi,Yamada, Taro,Domen, Kazunari
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- Enhancement of the electrical stability of ZnO varistors by a novel immersion process
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A novel immersion process was carried out to improve the electrical stability of ZnO varistors under a dc electrical field. It was performed by dipping the conventionally sintered ZnO varistor samples in a bismuth nitrate solution with a subsequent heat treatment. The results showed that this process could improve the electrical stability and the nonlinearity of the ZnO varistors simultaneously. All the immersed specimens exhibited a reduced leakage current and a stable nonlinearity in the dc degradation test. The optimum concentration of the immersion solution was found to be 1.0-2.0M. The microstructure and the electrical performance of the immersed ZnO varistors were investigated. This process generates an effective penetration of molten Bi2O3 from the surface into the interior, which compensates the near-surface bismuth loss that resulted from its vaporization during sintering. The extraneously penetrated molten Bi2O3 plus inherently molten Bi-rich phase facilitate the reconstruction of an intergranular layer and fills more grain boundaries with the γ-Bi2O3 phase. It is the abundant γ-Bi2O3 intergranular phase that improves the electrical stability by restraining the oxygen desorption at the grain boundary. The enhanced nonlinearity is related to the modification of the defect structure and the component distribution in the intergranular region.
- Meng, Lei,Zheng, Liaoying,Cheng, Lihong,Zheng, Yao,Li, Guorong,Bernik, Slavko
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- Thermal synthesis of the ZnO-Bi2O3 pigments
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A zinc oxide pigment with an admixture of bismut oxide has been prepared as new yellow pigment for colouring of plastics and paints. The effect of the Bi2O3 in the starting mixture on the colour hue of the pigment has been evaluated. The calcination conditions of the pigment synthesis have been established. The synthesis of these pigments was followed by thermal analysis using a derivatograph apparatus in our laboratory. The optimum conditions for the synthesis of pigments and the properties of the products have been estimated.
- Sulcova,Trojan
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