Molecular Catalysis
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2018
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IF 0
Gui Liu,Lei Sun,Wei Luo,Yue Yang,Junhua Liu,Fang Wang,Curtis J. Guild
Aerobic Baeyer-Villiger oxidation of ketones into corresponding esters were performed over mesoporous Mn-Ce and Mn-Co composite oxides prepared by co-impregnation method and benzaldehyde was used as the sacrificing agent. It was found that the best conversion and selectivity were obtained when the Mn/Ce mole ratio was 1:2 (denoted as Mn 0.33 Ce 0.67 O s ) through investigating the effect of Mn/Ce mole ratio on the catalytic activity. Interestingly, Mn 0.33 Co 0.67 O s (Mn/Co mole ratio was 1:2) catalyst had no catalytic activity for this reaction. X-ray diffraction (XRD) results showed that MnO x was completely dissolved into the CeO 2 lattice, and Mn 0.33 Co 0.67 O s sample was existed in the form of spinel structure (Co, Mn) (Mn, Co) 2 O 4 and obvious peaks of Co 3 O 4 . Nitrogen adsorption-desorption measurements revealed that Mn 0.67 Ce 0.33 O s , Mn 0.5 Ce 0.5 O s , Mn 0.33 Ce 0.67 O s and Mn 0.33 Co 0.67 O s materials possessed mesoporous structure. X-ray photoelectron spectroscopy (XPS) analysis showed that the highest concentration of Ce 3+ on the surface of Mn 0.33 Ce 0.67 O s catalyst, which could create unsaturated chemical bonds, charge imbalance, and oxygen vacancies on the surface of samples, it is beneficial to the oxidation reaction. Additionally, XPS data revealed that Mn 0.33 Ce 0.67 O s catalyst has great potential in catalytic oxidation due to the large amount of active oxygen species on the surface. In addition, manganese and cobalt species on the surface of Mn 0.33 Co 0.67 O s are almost present in the form of Mn 2+ and Co 3+ , it is known that Mn 2+ can serve as a potent antioxidant and scavenge the activity of active oxygen species, while Co 3+ ions can prevent the formation of oxygen vacancies and inhibit the release of reactive oxygen species, thus the presence of Mn 2+ and Co 3+ inhibited the catalytic activity of Mn 0.33 Co 0.67 O s catalyst. The diffuse reflectance ultraviolet-visible spectroscopy (DR-UV-vis) and hydrogen temperature-programmed reduction (H 2 -TPR) results are in accordance XPS data.
研究领域:
催化化学
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材料科学
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产品关联
DOI
APPLIED CATALYSIS B-ENVIRONMENTAL
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2021
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IF 19.503
Pengchao Ren,Weifeng Tu,Chanchan Wang,Sifan Cheng,Wenqi Liu,Zhenzhou Zhang,Yun Tian,Yi-Fan Han
This study investigated the Cu-CeO 2 interactions for CO hydrogenation to methanol by applying rate measurements, chemical titration/desorption, together with in-situ/operando spectroscopy techniques under realistic reaction conditions. Ce components were enriched in the surface region of Cu/CeO 2 catalysts while Ce 3+ and Ce 4+ atoms co-existed during CO hydrogenation. The ratio of Ce 3+ to Cu 0 in the surface region of catalysts increased linearly with the Ce content. The turnover rates of CH 3 OH formation increased as a single-valued function of the ratio, irrespective to the individual contact extent between Cu and CeO 2 clusters or Ce content in the Cu/CeO 2 catalysts, indicating that the Cu 0 -Ce 3+ sites pair acts as active sites for CO hydrogenation to methanol over Ce-CeO 2 samples. This study also unraveled that formyl and formate species, as reactive surface intermediates, were co-adsorbed on the Cu 0 -Ce 3+ sites, and their hydrogenation routes occurred concurrently for CH 3 OH formation during CO-H 2 reactions.
研究领域:
催化
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化学工程
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表面科学
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产品关联
DOI
高影响因子
Environmental Progress & Sustainable Energy
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2016
·Vol. 36
·期 2
·494-504
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IF 1.631
Zhengjiang Liu,Lei Xing,Huiyan Ma,Lin Cheng,Juming Liu,Jucai Yang,Qiancheng Zhang
Sulfated Ce-doped TiO 2 photocatalysts, with improved visible light photocatalytic activity, are prepared by sol-gel method and via impregnation with diluted sulfuric acid. The synthesized samples are characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet–visible diffuse reflectance spectra (UV–Vis DRS), Fourier transform infrared (FTIR) spectroscopy, temperature-programmed desorption of ammonia (NH 3 -TPD) and X-ray photoelectron spectroscopy (XPS). To investigate the effect of Ce doping as well as acid sites on the photoactivity of the synthesized photocatalyst, photocatalytic degradation of Rhodamine B in an aqueous solution is used as a probe reaction to evaluate the photocatalytic activity of the as-prepared samples under visible light irradiation. It reveals that Ce doping can improve the photocatalytic response of TiO 2 to visible light and the presence of Ce 4+ /Ce 3+ redox process facilitates the separation of photo-generated electrons and holes. In addition, the impregnation can create Lewis acid sites on the obtained catalyst surface. Lewis acid sites on the catalyst surface could increase the amount of adsorbed oxygen (O ad ) and consequently improve the transform efficiency of Ce 3+ to Ce 4+ . Thereafter an increase in the phtocatalytic activity of sulfated Ce-doped TiO 2 is achieved. The possible mechanism of RhB degradation by sulfated Ce-doped TiO 2 photocatalyst is preliminarily discussed. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 494–504, 2017
研究领域:
环境工程
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材料科学
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化学工程
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产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
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2024
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IF 5.8
Wenjie Deng,Decai Huang,Fengli Yang,Jiaqing Peng,Weixiong You,Xinyu Ye
Efficient cyan-emitting phosphor plays an important role in the development of solid-state lighting, which is indispensable to filling the cyan gap for full-spectrum warm-white light-emitting diodes (WLEDs) with high color rendering index (CRI). Herein, a novel highly efficient broadband cyan phosphor Ce 3+ -doped Ca 3 HfAl 2 Si 2 O 12 (CHASO: Ce 3+ ) garnet compound was developed by the substitution of Lu 3+ -Al 3+ with Ca 2+ -Hf 4+ /Si 4+ in Lu 3 Al 5 O 12 . The crystal structure and photoluminescence (PL) properties of CHASO: Ce 3+ were investigated in detail. Notably, CHASO: Ce 3+ phosphor can be effectively excited by violet light (390 – 430 nm) and exhibited bright cyan emissions around 490 nm with high PL internal quantum yields of 89.2 %. Moreover, the integrated PL intensity of the phosphor at 423 K was 66.3 % of that at room temperature. Finally, by incorporating CHASO: 11 %Ce 3+ with commercial blue/yellow/red phosphor onto a violet LED chip (400 nm), the prototype full-spectrum WLEDs device exhibits warm white light with high color rendering index (CRI, Ra and R9 > 90) and low correlated color temperature 3301 K. These results suggest the highly efficient phosphor CHASO: Ce 3+ is promising for low-blue full-spectrum healthy lighting.
研究领域:
材料科学
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光电技术
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固态照明
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DOI
高影响因子
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