通讯机构：
[Wang, WL; Wang, YL] C;Cent South Univ Forestry & Technol, Coll Sci, Changsha 410004, Hunan, Peoples R China.
关键词：
Cr(6+) and carmine;Electron beam irradiation;Heterostructure;In(2)S(3)-CdIn(2)S(4)@X(X = Ag, Ag(3)PO(4), AgI);Photocatalysis
摘要：
Ternary heterostructure nanotubes of In2S3-CdIn2S4@X(X=Ag, Ag3PO4, AgI) were synthesized with enhanced photocatalytic activity for efficiently degrading pollutants. Electron beam irradiation was employed to artificially introduce interface defects to the heterostructure nanotubes. The experimental results for degrading carmine and Cr(6+) under visible light irradiation showed that the photocatalytic efficiency of In2S3-CdIn2S4 was improved to some extent by the introduction of silver compounds. DRS results confirmed that the band gaps of In2S3-CdIn2S4 were reduced to 1.62eV and 1.58eV by introducing Ag3PO4 and AgI, respectively. Interestingly, the band gap of In2S3-CdIn2S4@AgI after electron beam irradiation was further reduced to 1.56eV, resulting in that the degradation time of both Cr(6+) and carmine by In2S3-CdIn2S4@AgI after high-energy electron beam irradiation was shortened to only 5min. The XRD spectra of the photocatalysts after five cycles could maintain the original crystal form to a large extent. The OH stretching vibration peaks of In2S3-CdIn2S4@AgI after electron beam irradiation at 3387cm(-1) became wider and sharper, thus indicating that the number of free hydroxyl groups on the heterostructure surface significantly increased. PL results showed that electron beam irradiation could significantly reduce the PL emission peak and enhance the utilization of photogenerated charge carriers. EIS results further confirmed that In2S3-CdIn2S4@AgI processed by electron beam irradiation had higher photogenerated electron-hole separation efficiency. Based on the experimental results, a feasible reaction pathway and photocatalytic mechanism for the degradation of carmine was investigated. ESR results showed that the main active groups in the whole photocatalytic system were *O2(-) and h(+).
摘要：
An efficient ternary heterostructure material Ag/Bi2WO6/CdWO4 was prepared via a facile hydrothermal route. The in situ loading precisely regulated the distribution of silver nanoparticles on the heterojunction surface. Besides, electron beam irradiation was used for artificially creating interface defects in the material, so the specific surface area of the material was increased. The introduction of defects was conducive for the migration of catalytically active substances towards the surface of the material. Under visible light irradiation, the degradation efficiency of the heterostructure material was improved significantly. Within 20 min, the removal efficiency of the treated material for carmine could reach about 100% (50 mL, 50 mg L-1), while that for hexavalent chromium (Cr6+), it could reach about 100% (50 mL, 10 mg L-1) within 90 min. In addition, the results showed that 4% Ag load rate had the best improvement on the photocatalytic performance of the ternary heterostructure material, irrespective of the degradation process of carmine, Cr6+ or rhodamine B (RhB). Optimum amount of supported in situ nano-silver induced resonance of the plasma on the catalytic interface and synergized with Bi3+ to improve the catalytic efficiency. PL, DRS and XPS results proved that the ternary heterostructure could effectively inhibit the rapid recombination of electron hole pairs of Ag/Bi2WO6/CdWO4. As for the role of electron beam irradiation, it could improve the content of free hydroxyl groups on the material surface and enhance the catalytic capacity of the Ag/Bi2WO6/CdWO4 heterogeneous material. A feasible reaction pathway and photocatalytic mechanism for the degradation of carmine was investigated by gas chromatography-tandem mass spectrometry (GC-MS), and the main role of OH in the catalytic process was obtained by using different scavengers.
期刊：
Chemical Physics,2018年502:77-86 ISSN：0301-0104
通讯作者：
Zhang, Ning;Zeng, Dewen
作者机构：
[Wang, Wenlei; Zhang, Ning] Cent South Univ Forestry & Technol, Coll Sci, Changsha 410004, Hunan, Peoples R China.;[Yi, Haibo; Zhang, Ning] Hunan Univ, Coll Chem & Chem Engn, Changsha 410082, Hunan, Peoples R China.;[Zeng, Dewen] Cent S Univ, Coll Chem & Chem Engn, Changsha 410083, Hunan, Peoples R China.;[Zhao, Zhongwei] Cent S Univ, Sch Met & Environm, Changsha 410083, Hunan, Peoples R China.;[Zhao, Zhongwei] Catalan Inst Nanosci & Nanotechnol ICN2, Campus UAB, Bellaterra 08193, Spain.
通讯机构：
[Zhang, Ning; Zeng, Dewen] C;Cent South Univ Forestry & Technol, Coll Sci, Changsha 410004, Hunan, Peoples R China.;Cent S Univ, Coll Chem & Chem Engn, Changsha 410083, Hunan, Peoples R China.
关键词：
Acidic solution;FPMD and DFT;Mo;Protonated ability;W
摘要：
In this work, we apply static density functional theory (DFT) calculations, as well as classical and first-principles molecular dynamics (FPMD) simulations, using the free-energy perturbation method to study the protonation ability, active site and structures of W(VI) and Mo(VI) in acidic aqueous solution. Using FPMD simulations, utilizing the pKa's calculation technique, we concluded that the octahedral WO2(OH)(2)(H2O)(2) is the true formula for tungstic acid (H2WO4), and the hydroxyl ligands are the acidic site. This aqueous structure of H2WO4 is analogous to the previously reported structure of molybdic acid (H2MoO4). The FPMD trajectories of the tungstic acid deprotonation show that the mono-protonated monotungstate ion (HWO4-) may partially exist as a five-coordinated WO3(OH)(H2O)(-) species except for the four-coordinated WO3(OH)(-) species. This result is supported by DFT calculations, with an isoenergetic point (Delta E = 1.9 kcal.mol(-1)) for the WO3(OH)(H2O)(-) and WO3(OH)(-) species, when explicit solvent molecules are taken into account. In contrast, for the H2MoO4 acid, FPMD trajectories during the deprotonation process show that two H2O ligands immediately escape from the first coordinated sphere of Mo (VI) to form the four-coordinated MoO3(OH)(-) species. This difference indicates that structural expansion of W(VI) began in the first protonated step, while that of Mo(VI) only occurs in the second step. In addition, our calculated first and second acid constants for tungstic acid are higher than previously reported values for molybdic acid. This result suggests that WO42- is more easily protonated than the MoO42- anion in the same acidic solution, which is further confirmed by DFT calculations of hydrated oxoanions and its protonated species, based upon the hydration energy. (C) 2018 Elsevier B.V. All rights reserved.
摘要：
<jats:title>Abstract</jats:title><jats:p>In this work, carbon quantum dots were first prepared through one-pot hydrothermal route of the propyl aldehyde and sodium hydroxide via an aldol condensation reaction, and a novel solid-phase extraction adsorbent of hollow calcite single crystals was prepared via the precipitation of metal nitrates by the CO<jats:sub>2</jats:sub> diffusion method in the presence of CQDs and further applied for excessive Cd(II) ions removal from water. The spectra and morphologies of the etched calcite were investigated by X-ray diffraction, Fourier transform infrared spectrometry, Scanning electron microscope, and Transmission electron microscopy. The results show that the CQDs etching technique successfully furnish a strategy for manufacturing interface defects onto the calcite crystal. Bath studies were done to evaluate the effects of the major parameters onto Cd(II) adsorption by the etched calcite, such as pH, contact time, and initial Cd(II) concentration. The Cd(II) adsorption onto the new adsorbent could reach a maximum adsorption amount of 66.68 mg/g at 120 min due to the abundant exterior adsorption sites on the adsorbent. The adsorption kinetics and adsorption isotherms of Cd(II) on the etched calcite were also investigated. The experimental datum showed that the adsorption kinetics and isotherms of Cd(II) on the etched calcite were well-fitted by the pseudo-second-order kinetic model and the Freundlich isotherm model respectively. The adsorption mechanisms could be primarily explained as the formation of Cd(OH)<jats:sub>2</jats:sub> and Ca<jats:sub>x</jats:sub>Cd<jats:sub>1−x</jats:sub>CO<jats:sub>3</jats:sub> solid solution on the adsorbent surface with the help of X-ray photoelectron spectroscopy.</jats:p>
作者机构：
[胡云楚; 王文磊; 陈秋菊; 王琼] School of Science, Central South University of Forestry and Technology, Changsha, 410004, China;[马莉萍; 谢奇龙] School of Materials Science and Engineering, Central South University of Forestry and Technology, Changsha, 410004, China
