POWDER METALLURGY AND METAL CERAMICS
·
2022
·Vol. 61
·期 3
·221-229
·
IF 0.913
Liang Dong,Xiong Sang,Zhang Xiaojuan,Lin Qing
Tungsten oxide is widely used in the photolysis of water for hydrogen production, photocatalysis, photoelectric conversion, and electrochromism. Eu 3+ doped tungsten trioxide nanoparticles were prepared by hydrothermal method with the addition of sodium tungstate (NaWO 4 · 2H 2 O). Two different samples were obtained at the temperature set at 160 and 180°C. The third sample obtained from ammonium paratungstate ((NH 4 ) 10 H 2 (W 2 O 7 ) 6 ) was used at the temperature of 160°C. The samples’ morphology, structure, and optical performance were then observed and analyzed. The results show that a rod-like structure of WO 3 : Eu 3+ nanoparticle with a monoclinic crystal system can be successfully generated using sodium tungstate. A spherical structure of WO 3 : Eu 3+ nanoparticle with a triclinic crystal system was prepared using ammonium paratungstate. The finished sample with ammonium paratungstate at a reaction temperature of 160°C has the smallest grain average size of 45.98 nm and Eu 3+ ions successfully doped. Under the excitation of different wavelengths, the three samples demonstrate pronounced emission peaks at around 615 nm, corresponding to the 5D 0 → 7F 2 electronic transition of Eu 3+ . Using ammonium paratungstate as the tungsten source, the prepared WO 3 : Eu 3+ nanoparticle at 160°C has the highest luminous intensity. The luminescence intensity of the prepared WO 3 : Eu 3+ nanoparticle from ammonium paratungstate as a tungsten source is higher than the other two samples obtained from sodium tungstate as a tungsten source at two temperatures. However, the three samples with excitation wavelength λ = 254 nm were monitored at the wavelength of 615 nm. All three samples exhibited the most substantial excitation peaks at about 508 nm, which belonged to the electron transition in 4f of Eu 3+ .
研究领域:
材料科学
·
光学
✓ 已验证
DOI
高影响因子
CHEMICAL GEOLOGY
·
2019
·
IF 3.618
Xiaolin Wang,Ye Qiu,Jianjun Lu,I-Ming Chou,Wenlan Zhang,Guanglai Li,Wenxuan Hu,Zhen Li,Richen Zhong
Knowledge on hydrothermal tungsten (W) species is vital towards a better understanding of tungsten transport and mineralization mechanisms. In this study, in situ Raman spectra of a 0.005 – 0.1 mol/kg ( m ) K 2 WO 4 solution containing CO 2 , HCl, and NaHCO 3 were collected at 50–400 °C and 20–60 MPa. The spectra for the symmetric stretching vibration mode of the W O bond, v 1 (W O), were analyzed to investigate the hydrothermal tungstate species. Results showed that carbonate/bicarbonate do not associate with tungstate to form carbonic tungstate species. Nevertheless, the presence of CO 2 can increase the fluid acidity, which favors the formation of polymeric tungstate species at <300 °C. Above about 300 °C, monomeric tungstates (e.g., WO 4 2- , HWO 4 -, H 2 WO 4 and alkali tungstate ion pairs) are responsible for the hydrothermal transport of tungsten, and the v 1 (W O) modes of these species are centered at ∼930 cm -1 and 950 cm -1 . Based on the above observations, we simulated the mineralization process in the context of fluid-rock interactions using tungstate and alkali tungstate ion pairs as the only aqueous W species. The thermodynamic simulations showed that (a) the timing of mineralization mainly depends on the W concentration in the initial mineralizing fluid and the availability of Ca 2+ , Fe 2+ and Mn 2+ , with higher W concentrations generally favoring higher temperature mineralization; (b) highly W-enriched fluid is not essential for W mineralization, while extremely low contents of Fe, Mn and Ca in the magma are useful to maintain the mobility of aqueous W until favorable host rocks are encountered; and (c) a “hydrogen reservoir” effect was identified for dissolved CO 2 . The presence of CO 2 can promote the extraction of Fe(II) from the pelitic host rocks, thereby facilitating a high-grade vein-type W mineralization. At <∼300 °C, polytungstate species, whose v 1 (W O) modes are centered at ∼965 – 995 cm -1 , are important hydrothermal W species along with monomeric tungstates. Therefore, polymeric tungstate species should be considered in future thermodynamic modeling of W transport and mineralization at <300 °C. An increase in fluid pH induced by CO 2 -escape and/or fluid-rock interactions will destabilize the polymeric tungstates to form WO 4 2- and other monomeric tungstate, which interacts with metal cations to form wolframite and/or scheelite.
研究领域:
地球化学
·
矿物学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY
·
2023
·
IF 6.1
Zhiquan Chen,Yinshan Liu,Lei Ni,Juncheng Jiang,Yuan Yu,Yong Pan,Zhichao Zhu
To overcome the problems of traditional catalyst in the microreaction technology, a microreactor system with tungstate metal foam catalyst was constructed and the catalytic efficiency were investigated by dimethyl sulfoxide (DMSO) oxidation reaction as a probe reaction. Three tungstate metal (CuWO 4 , NiWO 4 , FeWO 4 ) foams were fabricated, and inherited the porous structure from the metal foam and had a high loading density of tungstate metal crystal particles. In the lab-built flat-plate microreactor, the effects of reaction temperature, residence time, molar ratio and pH on the yield of dimethyl sulfone (MSM) were investigated, and the tungstate metal foams showed prefect catalytic activity. Compared with NiWO 4 foam and FeWO 4 foam, the larger specific surface area and higher porosity endow CuWO 4 with a better catalytic performance. When the reaction temperature was 80 °C, the residence time was 40 min, the molar ratio was 1:1 and the pH value of the reaction system was 3, the yield of MSM reached 82.1%. Furthermore, the NiWO 4 foam catalyst system showed a better performance compared with other two catalyst system. This work indicates the potential opportunity of the construction of various metal foam catalysts in the versatile continuous microreaction technology.
研究领域:
化学工程
·
催化材料科学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2022
·
IF 16.744
Hao Jiang,Yian Wang,Jue Hu,Xuxia Shai,Chengxu Zhang,Thiquynhxuan Le,Libo Zhang,Minhua Shao
Hydrogen peroxide (H 2 O 2 ), as one of the most important chemicals, is widely applied in many industries. Electrocatalytic oxygen reduction provides a safe and on-site method for H 2 O 2 synthesis. The research of transition metal oxides (TMOs) for H 2 O 2 synthesis is mainly focused on the modification of transition metal elements and graphene. Few studies directly control pure TMOs without changing supporting materials or introducing other elements. Here, we demonstrate for the first time a phase regulation strategy to develop highly selective and stable tungsten trioxide catalysts for H 2 O 2 generation through 2e − oxygen reduction reaction (2e − ORR). DFT calculations show that the kinetic energy barrier (0.08 eV) of the 2e − ORR pathway on the cubic tungsten trioxide (c-WO 3 ) surface is much lower than that of the 4e − ORR pathway (0.76 eV). As a result, a selectivity of 90 % and H 2 O 2 production rate of 179 mmol g cat −1 h −1 are achieved at 0.1 V vs RHE under alkaline conditions, outperforming all catalysts previously reported under the same conditions. Moreover, after continuous testing for more than 24 h at a constant potential of 0.1 V vs RHE, the H 2 O 2 generation rate has not been diminished, indicating an excellent stability of c-WO 3 in practical applications.
研究领域:
材料科学
·
电化学
·
催化科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS
·
2020
·
IF 3.442
Yihan Liu,Lina Kong,Xin Guo,Jianping Xu,Shaobo Shi,Lan Li
The construction of surface defects on semiconductor oxide photoanodes has been identified as a promising route for attaining improved photoelectrochemical (PEC) performance. Here, Ar plasma treatment has been used to etch the surface of hydrothermally synthesized WO 3 nanoplate array films, which generated surface oxygen vacancies (O v s) with the concomitant reduction of surface W 6+ to W 5+ /W 4+ . As a result, the visible-light absorption and photogenerated charge separation of WO 3 was enhanced, as evidenced by X-ray photoelectron spectroscopy (XPS), UV/Vis diffuse-reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. A WO 3 photoanode subjected to Ar plasma treatment for 120 s exhibited a photocurrent density of 1.32 mA cm −2 and an O 2 evolution rate of 1.0 μmol cm −2 ·min −1 under simulated solar light irradiation at a bias potential of 1.23 V vs. reversible hydrogen electrode, approximately 1.7- and 5-times higher, respectively, than those of a pristine sample. This improvement is mainly attributed to the facilitative effect of surface oxygen vacancy defects, which promote electron–hole generation and separation rates and decrease the interfacial charge-transfer resistance between the WO 3 photoanode and electrolyte. Our Ar plasma surface modification also has potential for developing other photoanodes for efficient PEC performance.
研究领域:
材料科学
·
能源科学
✓ 已验证
产品关联
DOI
高影响因子
FUEL
·
2021
·
IF 6.609
Zhi Yang,Bowen Luo,Riyang Shu,Zhipeng Tian,Yu Kang,Ying Chen
An effective binary catalyst by using tungstic acid (H 2 WO 4 ) and Ru/C was employed for the hydrodeoxygenation (HDO) of phenolic compounds and raw lignin-oil. H 2 WO 4 was presented as solid at ambient temperature, but it dissolved at high temperature above 100 °C and therefore functioned as an active homogeneous catalyst. This phenomenon resulted in a temperature-controlled phase-transfer behavior in the HDO of phenolic compounds. An efficient HDO performance and an exceptional reusability for guaiacol HDO were presented by this bifunctional catalyst, which can be reused more than 10 times with guaiacol conversion and cyclohexane selectivity over 90%. The comparison of traditional liquid organic and mineral acids, as well as solid acids, with H 2 WO 4 confirmed the outstanding catalytic performance of H 2 WO 4 and highlighted the advantages of H 2 WO 4 as a homogeneous catalyst. Besides guaiacol, other phenolic compounds including various monomers and dimers all exhibited good HDO results, with 100% conversion and cycloalkanes selectivity. Moreover, the raw lignin-oil can be efficiently deoxygenated under the catalysis of this bifunctional catalyst. 99.3% content of hydrocarbons was obtained in the upgraded lignin-oil, which was promising to be used as fuel directly. This catalytic system has great potential for the industrial application of lignin-oil upgrade.
研究领域:
化学工程
·
可再生能源
✓ 已验证
产品关联
DOI
高影响因子
INORGANICA CHIMICA ACTA
·
2022
·
IF 3.118
Mingyan Chen,Dehua Zhang,Ziying Wang,Yao Zhang,Yucheng Liu
UiO-66 loading carboxyl and phosphotungstic acid has a good affinity to thiophene (TH). The synthesized catalyst, changed its original structure, which can increase its reactive site and enhance the interaction with thiophene (TH) in order to improve the adsorption performance. Then the structural changes were analyzed by XRD, FT-IR, SEM, BET, EDS and other characterization methods. Through static experiments of adsorption desulfurization, it is found that when the adsorption time is 240 min, the adsorption temperature is 30 ℃ and the oil-to-agent ratio is 100:1, the adsorption effect: UiO-66-(COOH) 2 (UC2) > UiO-66, the highest adsorption capacity can reach 89.99 mg/g; while PTA@UiO-66 (PAU) can reach adsorption equilibrium at 210 min, it has better desulfurization performance than UiO-66. After being recycled for 5 times, the adsorption effect is only slightly decreased: the adsorption capacity of UC2 was still 78.02% of the initial adsorption capacity, while that of PAU was 76.07% of the initial adsorption capacity. According to the adsorption kinetics, the adsorption process of thiophene on the adsorbent UC2 is more consistent with W-M model, and the adsorption of PAU is more in line with the pseudo-first order kinetic equation. In addition, it also includes the process of intraparticle diffusion and liquid film diffusion.
研究领域:
化学工程
·
材料科学
✓ 已验证
DOI
高影响因子
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
·
2024
·
IF 4.3
Cong Xiang,Jingyi Fang,Yanlin Huang,Zhuo Zheng,Hyo Jin Seo
Eu 3+ is not only a major red-emitting activator, but also an excellent spectral probe ion. This work reports the Eu 3+ -sites and luminescence in the cation-deficient perovskite tungstates, A-site deficient SrLa 2 (Mg 2 W 2 )O 12 [Sr 1/2 □ 1/2 La(MgW)O 6 ] and B-site deficient Sr 2 La 2 (MgW 2 )O 12 [SrLa(Mg 1/2 □ 1/2 W)O 6 ]. The 7 F 0 → 5 D 0 excitation spectra of Eu 3+ activators in two lattices were measured via pulsed dye laser. In SrLa 2 (Mg 2 W 2 )O 12 :Eu 3+ , there is only one 7 F 0 → 5 D 0 transition, which could be related to the Eu 3+ center on La 3+ sites; while, two 7 F 0 → 5 D 0 transitions in Sr 2 La 2 (MgW 2 )O 12 indicate Eu 3+ ions occupy Sr 2+ in addition to La 3+ , resulting in the luminescent centers related to heterovalent substitution defects. The different Eu 3+ sites make two phosphors exhibit different red luminescence properties. SrLa 2 (Mg 2 W 2 )O 12 :Eu 3+ shows higher luminescent efficiency and thermal quenching due to its regular distribution of the activators resulting in lower dispersion losses of the energy transfer. The experimental results show that rare earth ions occupy different crystallographic positions in A -site and B -site deficient perovskite oxides, and this microstructure can be important for the corresponding luminescent properties.
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHEMICAL ENGINEERING JOURNAL
·
2018
·
IF 6.735
Zhuocheng Yin,Yuyu Bu,Jun Ren,Shuai Chen,Daming Zhao,Yihui Zou,Shaohua Shen,Dongjiang Yang
Tungsten trioxide (WO 3 ) is believed to be a promising electrode candidate for supercapacitors, due to its reversible surface redox reaction resulted from the almost same W-O bond lengths with different oxidation states. However, the specific capacitance of WO 3 electrode is very low (<250 mF cm −2 ) because of its low conductivity and slow surface redox reaction kinetics. Herein, to address these issues, mesoporous WO 3 nanosheets with exposed (2 0 0) facets were anchored on activated carbon cloth (ACC) via a simple two-step process including heat treatment and alcohol-thermal process. The ACC was coated on WO 3 seeds and proceed a heat treatment at 500 °C and the time of alcohol-thermal process were 7 h, 8 h, and 9 h labeled as WO 3 @ACC- n ( n = 7, 8, 9). SEM and TEM images confirmed the WO 3 nanosheets were successful anchored on the ACC. The WO 3 @ACC-8 electrode showed the best specific areal capacitance which could reach as high as 659 mF cm −2 at a current density of 5 mA cm −2 and superior stability with almost no decrease in 10,000 cycles in the presence of Na 2 SO 4 as the neutral electrolyte. The capacitance is encouragingly much higher than the previously reported values in a three-electrode system in the neutral aqueous condition. DFT calculations reveal that, in comparison to the (0 0 2) and (0 2 0) facets, the exposed (2 0 0) facets of the mesoporous WO 3 nanosheets triggers the superior Na + adsorption, which accelerates the Na + -involved surface redox reaction for the boosted supercapacitor performance. A flexible asymmetric supercapacitor (FASC) was fabricated from the WO 3 @ACC electrode, which exhibits high energy density (0.5 mWh cm −3 ) and power density (62 mW cm −3 ) without any attenuation during ±180° wide-angle bending.
研究领域:
材料科学
·
电化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF MATERIALS SCIENCE
·
2019
·Vol. 54
·期 22
·13914-13937
·
IF 3.442
Pudukudy Manoj,Jia Qingming
A controlled acidic precipitation is reported for the direct synthesis of nanosheets self-assembled hierarchical tungstic acid microspheres, and their annealing-dependent thermal conversion into WO 3 microstructures is studied for the first time. The synthesis was carried out without the use of any structure directing agents and hydrothermal conditions. The microspheres were found to be consisting of many single-crystalline and highly oriented nanosheets that were hierarchically self-aggregated in spherical form for the minimization of surface energy. An experimentally validated time-dependent formation and growth mechanism was proposed for the development of microspheres. The characterization results indicated that the morphology-preserved thermal decomposition of H 2 WO 4 into WO 3 microspheres occurred at 400 °C, whereas a morphology distortion was noticed for the sample synthesized at 600 °C. The increase in annealing temperature further increased the crystallinity of WO 3 without changing its monoclinic crystal structure. However, it has a diminishing effect in the specific surface area, pore size and pore volume of the annealed samples. Moreover, the adsorption of methylene blue in aqueous medium was carried out to evaluate its potential environmental application. The WO 3 microspheres synthesized at 400 °C showed high adsorption capacity (63 mg/g) compared to the same at 600 °C (56 mg/g). The high activity could be ascribed to the synergistic effects of high surface area, low particle size, porosity, specific morphology and more negative zeta potential. The adsorption further followed pseudo-second-order kinetics with a best fit of the experimental and theoretical values.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
APPLIED CATALYSIS A-GENERAL
·
2015
·
IF 3.942
Gang Xu,Aiqin Wang,Jifeng Pang,Mingyuan Zheng,Jianzhong Yin,Tao Zhang
Cellulose is the most abundant biomass in nature, and its catalytic conversion to commodity chemical ethylene glycol represents an important advance towards sustainable chemistry. In previous work, we have shown that tungstic acid plays a key role in selective C–C cleavage to form glycolaldehyde and then ethylene glycol. To further enhance the efficiency of tungstic acid, a series of additives were investigated in this work. Among various acid additives, H 2 SO 4 stands out as the most remarkable additive; ethylene glycol yield was enhanced from 32.6% to 52.6% at a H 2 SO 4 /H 2 WO 4 molar ratio of 0.03 and a H 2 WO 4 /cellulose weight ratio of 0.05, that is, an extremely dilute acid concentration. Weakly acidic sulfates (e.g., CuSO 4 and FeSO 4 ) have also been demonstrated to be highly efficient additives to improve the catalytic efficiency of tungstic acid, through promoting the hydrolysis of cellulose.
研究领域:
化学工程
·
可持续化学
✓ 已验证
产品关联
DOI
高影响因子
Catalysts
·
2015
·Vol. 5
·期 4
·1897-1910
·
IF 2
Shiqiang Zhao,Guizhuan Xu,Chun Chang,Shuqi Fang,Ze Liu,Fengguang Du
A series of metal-modified phosphotungstates were prepared and performed for direct synthesis of ethyl levulinate from fructose in ethanol. Considering the cost of catalysts, catalytic activity of catalysts, and easy separation of catalysts together, K-HPW-1 was chosen as the most suitable catalyst for synthesis of ethyl levulinate from fructose. A high ethyl levulinate yield of 64.6 mol% was obtained at 150 °C within 2 h in ethanol. The introduction of low polar toluene as a co-solvent improved the yield of ethyl levulinate to 68.7 mol%. The recovered catalyst remained high activity with the yield of ethyl levulinate converted from fructose above 50 mol% after being used five times. Moreover, the generality of the catalyst was further demonstrated by glucose, sucrose, inulin, and cellulose with ethyl levulinate yielding 14.5, 35.4, 52.3, and 14.8 mol%, respectively.Keywords:ethyl levulinate;carbohydrates;potassium phosphotungstate
研究领域:
催化化学
·
可再生化学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）