The electrocatalytic oxidation of methanol was studied over Ni, Co and Cu binary or ternary alloys on graphite electrodes in a NaOH solution （0.1 mol/L）. The catalysts were prepared by cycling the graphite electrode...The electrocatalytic oxidation of methanol was studied over Ni, Co and Cu binary or ternary alloys on graphite electrodes in a NaOH solution （0.1 mol/L）. The catalysts were prepared by cycling the graphite electrode in solutions containing Ni, Cu and Co ions at cathodic potentials. The synergistic effects and catalytic activity of the modified electrodes were investigated by cyclic voltammetry （CV）, chronoamperometry CCA） and electrochemical impedance spectroscopy （EIS）. It was found that, in the presence of methanol, the modified Ni-based ternary alloy electrode （G/NiCuCo） exhibited a significantly higher response for methanol oxidation compared to the other samples. The anodic peak currents showed a linear dependency on the square root of the scan rate, which is a characteristic of a diffusion controlled process. During CA studies, the reaction exhibited Cottrellin behavior and the diffusion coefficient of methanol was determined to be 6.25× 10-6 cm2/s and the catalytic rate constant, K, for methanol oxidation was found to be 40×107 cm3/Cmol.s）. EIS was used to investigate the catalytic oxidation of methanol on the surface of the modified electrode.展开更多
Alloying degree, particle size and the level of dispersion are the key structural parameters of Pt-Ru/C catalyst in fuel cells. Solvent（s） used in the preparation process can affect the particle size and alloying de...Alloying degree, particle size and the level of dispersion are the key structural parameters of Pt-Ru/C catalyst in fuel cells. Solvent（s） used in the preparation process can affect the particle size and alloying degree of the object substance, which lead to a great positive impact on its properties. In this work, three types of solvents and their mixtures were used in preparation of the Pt-Ru/C catalysts by chemical reduction of metal precursors with sodium borohydride at room temperature. The structure of the catalysts was characterized by X-ray diffraction （XRD） and Transmission electron microscopy （TEM）. The catalytic activity and stability for methanol electro-oxidation were studied by Cyclic Voltammetry （CV） and Chronoamperometry （CA）. Pt-Ru/C catalyst prepared in H2O or binary solvents of H2O and isopropanol had large particle size and low alloying degree leading to low catalytic activity and less stability in methanol electro-oxidation. When tetrahydrofuran was added to the above solvent systems, Pt-Ru/C catalyst prepared had smaller particle size and higher alloying degree which resulted in better catalytic activity, lower onset and peak potentials, compared with the above catalysts. Moreover, the catalyst prepared in ternary solvents of isopropanol, water and tetrahydrofuran had the smallest particle size, and the high alloying degree and the dispersion kept unchanged. Therefore, this kind of catalyst showed the highest catalytic activity and good stability for methanol electro-oxidation.展开更多
The salt effects on molecular orientation at air/liquid methanol interface were investigated by the polarization-dependent sum frequency generation vibrational spectroscopy（SFG-VS）. We clarified that the average til...The salt effects on molecular orientation at air/liquid methanol interface were investigated by the polarization-dependent sum frequency generation vibrational spectroscopy（SFG-VS）. We clarified that the average tilting angle of the methyl group to be u = 308 58 at the air/pure methanol surface assuming a d-function orientational distribution. Upon the addition of 3 mol/L Na I, the methyl group tilts further away from the surface normal with a new u = 418 38. This orientational change does not explain the enhancement of the SFG-VS intensities when adding Na I, implying the number density of the methanol molecules with a net polar ordering in the surface region also changed with the Na I concentrations. These spectroscopic findings shed new light on the salt effects on the surfaces structures of the polar organic solutions. It was also shown that the accurate determination of the bulk refractive indices and Raman depolarization ratios for different salt concentrations is crucial to quantitatively interpret the SFG-VS data.展开更多
The effect of chloride ions on a monoclinic ZrO2-supported RuOx （RuOx/m-ZrO2） catalyst with a Ru surface density of 0.3 Ru/nm2 was studied in the selective oxidation of methanol to methyl formate （MF） at a low tem...The effect of chloride ions on a monoclinic ZrO2-supported RuOx （RuOx/m-ZrO2） catalyst with a Ru surface density of 0.3 Ru/nm2 was studied in the selective oxidation of methanol to methyl formate （MF） at a low temperature of 373 K. The m-ZrO2 support was Cl-free, and Cl- ions were introduced into the RuOx/m-ZrO2 catalyst by impregnation with zirconium oxychloride or ammonium chloride and subsequent thermal treatment in air at 673 K. The structures of these catalysts were characterized by X-ray diffraction, Raman and X-ray photoelectron spectroscopies. Their reducibility was probed by temperature-programmed reduction in H2. The RuOx domains were present as highly dispersed Rut42- structure on m-ZrO2 with similar reducibility for the RuOx/m-ZrO2 samples irrespective of modification with or without Cl ions. Introduction of appropriate amounts of zirconium oxychloride into RuOx/m-ZrO2 led to a remarkable increase in the methanol oxidation rate and MF selectivity, whereas introduction of ammonium chloride or zirconyl nitrate significantly inhibited the catalytic performance of RuOx/m-ZrO2. The promoting effect of Cl- ions derived from zirconium oxychloride can be tentatively attributed to their roles in facilitating the adsorption of methanol and desorption of MF product or its intermediates. This finding provides novel insights into the promoting effect of Cl- ions on oxides-based catalysts for selective oxidation reactions.展开更多
Objective:In Port Harcourt and its environs,extracts of Cleistopholis patens are used by traditional medicine healers for the treatment of menstrual irregularities and other gynaecological disorders.The objective of t...Objective:In Port Harcourt and its environs,extracts of Cleistopholis patens are used by traditional medicine healers for the treatment of menstrual irregularities and other gynaecological disorders.The objective of this study was therefore to determine the effects of orally administered methanol extract of the stem bark of Cleistopholis patens on the reproductive organs of non-pregnant albino(Wistar) rats.Methods:3g/kg(low dose) and 6g/kg(high dose) of the extract were administered orally,daily to two different groups of animals,respectively, over a period of 28 days.A third(control) group of animals received distilled water only,orally over the same period.Five animals from each of the groups were sacrificed on day 8,15 and 29.Venous blood samples and reproductive organs respectively were taken from each group of sacrificed animals for hormonal and histopathological analysis.Results:Results of the hormonal assay revealed a general increase in the levels of Follicle Stimulating Hormone(FSH),Luteinizing Hormone(LH),progesterone,and estrogen.The highest levels were noticed in the animals sacrificed on the 29th day(LH =5.48±0.04 IU/L;FSH =3.80±0.00 IU/ L;Progesterone =7.14±0.15 nmol/L;Estrogen = 0.168±0.002 nmol/L).These increases were statistically significant compared to those of the control animals(LH =2.90±0.00 IU /L;FSH = 1.28±0.02 IU/L; Progesterone = 3.80±0.00 nmol/L;Estrogen = 0.130±0.002 nmol/L;P【0.05),and were also dose dependent. Results of the histopathological studies showed presence of chronic inflammatory cells in the tissues of the fallopian tubes and uterus on the 29th day.However,no changes were observed in the ovaries.Conclusion: The administration of the extract produced a dose and time-dependent increase in FSH,LH,progesterone and estrogen levels.We postulate that these observed effects may have been induced by the phytoestrogens (known to have 1/1 000 th of the efficacy of natural oestrogens) in the extract.The hormonal and histopathological changes may explain the effects described by patients following ingestion of extracts of this plant in traditional medical practice.However,it remains to be determined if these effects are harmful or beneficial in disease conditions.展开更多
CeO 2 improves the activity and selectivity of Pd/Al 2O 3 catalyst for methanol decomposition. The interaction between Pd and CeO 2 was then proposed to result in the promoting effect. The selectivity of CO and H ...CeO 2 improves the activity and selectivity of Pd/Al 2O 3 catalyst for methanol decomposition. The interaction between Pd and CeO 2 was then proposed to result in the promoting effect. The selectivity of CO and H 2 is significantly improved by addition of La 2O 3 to either Pd/Al 2O 3 or Pd/CeO 2/Al 2O 3 catalysts. Moreover, a synergistic promotion between CeO 2 and La 2O 3 on γ Al 2O 3 supported Pd catalysts was observed for the catalytic activity towards methanol decomposition into CO and H 2.展开更多
A series of novel carbon nanofibers(CNFs)based Cu-ZrO2 catalysts were synthesized by deposition precipitation method.To investigate the influence of promoter,catalysts were loaded with 1,2,3 and 4 wt%ZnO and character...A series of novel carbon nanofibers(CNFs)based Cu-ZrO2 catalysts were synthesized by deposition precipitation method.To investigate the influence of promoter,catalysts were loaded with 1,2,3 and 4 wt%ZnO and characterized by ICP-OES,HRTEM,BET,N2O chemisorption,TPR,XPS and CO2-TPD techniques.The results revealed that physicochemical properties of the catalysts were strongly influenced by incorporation of ZnO to the parent catalyst.Copper surface area(SCu)and dispersion(DCu)were slightly decreased by incorporation of ZnO promoter.Nevertheless,SCuand DCuwere remarkably decreased when ZnO content was exceeded beyond 3 wt%.The catalytic performance was evaluated by using autoclave slurry reactor at a pressure and temperature of 30 bar and 180℃,respectively.The promotion of CuZrO2/CNFs catalyst with 3 wt%of ZnO enhanced methanol synthesis rate from 32 to 45 g kg^-1 h^-1.Notably,with the ZnO promotion the selectivity to methanol was enhanced to 92%compared to 78%of the un-promoted Cu-ZrO2/CNFs catalyst at the expense of a lowered CO2 conversion.In addition,the catalytic activity of this novel catalyst system for CO2 hydrogenation to methanol was compared with the recent literature data.展开更多
We present a straightforward physical approach for synthesizing multiwalled carbon nanotubes(CNTs)-Pd Au/Pt trimetallic nanoparticles(NPs), which allows predesign and control of the metal compositional ratio by simply...We present a straightforward physical approach for synthesizing multiwalled carbon nanotubes(CNTs)-Pd Au/Pt trimetallic nanoparticles(NPs), which allows predesign and control of the metal compositional ratio by simply adjusting the sputtering targets and conditions. The small-sized CNTs-Pd Au/Pt NPs(~3 nm, Pd/Au/Pt ratio of 3:1:2) act as nanocatalysts for the methanol oxidationreaction(MOR), showing excellent performance with electrocatalytic peak current of 4.4 A mg^(-1) Pt and high stability over 7000 s. The electrocatalytic activity and stability of the Pd Au/Pt trimetallic NPs are much superior to those of the corresponding Pd/Pt and Au/Pt bimetallic NPs,as well as a commercial Pt/C catalyst. Systematic investigation of the microscopic, crystalline, and electronic structure of the Pd Au/Pt NPs reveals alloying and charge redistribution in the Pd Au/Pt NPs, which are responsible for the promotion of the electrocatalytic performance.展开更多
A catalytic reaction over a silver catalyst performed in an unregarded temperature region（473-873 K） with a long catalytic lifetime for the production of methyl formate from methanol was provided as a potential prep...A catalytic reaction over a silver catalyst performed in an unregarded temperature region（473-873 K） with a long catalytic lifetime for the production of methyl formate from methanol was provided as a potential preparing route. The optimal yield of methyl formate（ca. 14. 8% ） with a selectivity 〉90% was obtained at about 573 K. Because α- oxygen species and bulk oxygen species coexist in the unregarded temperature region, a synergistic process concerning α-oxygen species and bulk oxygen species was proved over Oα -rich and Oγ-rich samples.展开更多
基金provided by K.N.Toosi University of Technology Research Council to conduct this research
文摘The electrocatalytic oxidation of methanol was studied over Ni, Co and Cu binary or ternary alloys on graphite electrodes in a NaOH solution （0.1 mol/L）. The catalysts were prepared by cycling the graphite electrode in solutions containing Ni, Cu and Co ions at cathodic potentials. The synergistic effects and catalytic activity of the modified electrodes were investigated by cyclic voltammetry （CV）, chronoamperometry CCA） and electrochemical impedance spectroscopy （EIS）. It was found that, in the presence of methanol, the modified Ni-based ternary alloy electrode （G/NiCuCo） exhibited a significantly higher response for methanol oxidation compared to the other samples. The anodic peak currents showed a linear dependency on the square root of the scan rate, which is a characteristic of a diffusion controlled process. During CA studies, the reaction exhibited Cottrellin behavior and the diffusion coefficient of methanol was determined to be 6.25× 10-6 cm2/s and the catalytic rate constant, K, for methanol oxidation was found to be 40×107 cm3/Cmol.s）. EIS was used to investigate the catalytic oxidation of methanol on the surface of the modified electrode.
基金supported by 863 Project(No.2006AA05Z102)the Cultivation Fund of the Key Scientific and Technical Innovation Project,Ministry of Education of China (No.707050)+1 种基金Specialized Research Fund for the Doctoral Program of Higher Education (No.20060610023)Chengdu Natural Science Foundation (Nos.06GGYB449GX-030,and 07GGZD139GX)
文摘Alloying degree, particle size and the level of dispersion are the key structural parameters of Pt-Ru/C catalyst in fuel cells. Solvent（s） used in the preparation process can affect the particle size and alloying degree of the object substance, which lead to a great positive impact on its properties. In this work, three types of solvents and their mixtures were used in preparation of the Pt-Ru/C catalysts by chemical reduction of metal precursors with sodium borohydride at room temperature. The structure of the catalysts was characterized by X-ray diffraction （XRD） and Transmission electron microscopy （TEM）. The catalytic activity and stability for methanol electro-oxidation were studied by Cyclic Voltammetry （CV） and Chronoamperometry （CA）. Pt-Ru/C catalyst prepared in H2O or binary solvents of H2O and isopropanol had large particle size and low alloying degree leading to low catalytic activity and less stability in methanol electro-oxidation. When tetrahydrofuran was added to the above solvent systems, Pt-Ru/C catalyst prepared had smaller particle size and higher alloying degree which resulted in better catalytic activity, lower onset and peak potentials, compared with the above catalysts. Moreover, the catalyst prepared in ternary solvents of isopropanol, water and tetrahydrofuran had the smallest particle size, and the high alloying degree and the dispersion kept unchanged. Therefore, this kind of catalyst showed the highest catalytic activity and good stability for methanol electro-oxidation.
基金supported by the National Natural Science Foundation of China (Nos. 21227802, 21303216 and 21473217)
文摘The salt effects on molecular orientation at air/liquid methanol interface were investigated by the polarization-dependent sum frequency generation vibrational spectroscopy（SFG-VS）. We clarified that the average tilting angle of the methyl group to be u = 308 58 at the air/pure methanol surface assuming a d-function orientational distribution. Upon the addition of 3 mol/L Na I, the methyl group tilts further away from the surface normal with a new u = 418 38. This orientational change does not explain the enhancement of the SFG-VS intensities when adding Na I, implying the number density of the methanol molecules with a net polar ordering in the surface region also changed with the Na I concentrations. These spectroscopic findings shed new light on the salt effects on the surfaces structures of the polar organic solutions. It was also shown that the accurate determination of the bulk refractive indices and Raman depolarization ratios for different salt concentrations is crucial to quantitatively interpret the SFG-VS data.
基金supported by the National Natural Science Foundation of China(20825310 and 20973011)National Basic Research Project of China (2011CB201400 and 2011CB808700)
文摘The effect of chloride ions on a monoclinic ZrO2-supported RuOx （RuOx/m-ZrO2） catalyst with a Ru surface density of 0.3 Ru/nm2 was studied in the selective oxidation of methanol to methyl formate （MF） at a low temperature of 373 K. The m-ZrO2 support was Cl-free, and Cl- ions were introduced into the RuOx/m-ZrO2 catalyst by impregnation with zirconium oxychloride or ammonium chloride and subsequent thermal treatment in air at 673 K. The structures of these catalysts were characterized by X-ray diffraction, Raman and X-ray photoelectron spectroscopies. Their reducibility was probed by temperature-programmed reduction in H2. The RuOx domains were present as highly dispersed Rut42- structure on m-ZrO2 with similar reducibility for the RuOx/m-ZrO2 samples irrespective of modification with or without Cl ions. Introduction of appropriate amounts of zirconium oxychloride into RuOx/m-ZrO2 led to a remarkable increase in the methanol oxidation rate and MF selectivity, whereas introduction of ammonium chloride or zirconyl nitrate significantly inhibited the catalytic performance of RuOx/m-ZrO2. The promoting effect of Cl- ions derived from zirconium oxychloride can be tentatively attributed to their roles in facilitating the adsorption of methanol and desorption of MF product or its intermediates. This finding provides novel insights into the promoting effect of Cl- ions on oxides-based catalysts for selective oxidation reactions.
文摘Objective:In Port Harcourt and its environs,extracts of Cleistopholis patens are used by traditional medicine healers for the treatment of menstrual irregularities and other gynaecological disorders.The objective of this study was therefore to determine the effects of orally administered methanol extract of the stem bark of Cleistopholis patens on the reproductive organs of non-pregnant albino(Wistar) rats.Methods:3g/kg(low dose) and 6g/kg(high dose) of the extract were administered orally,daily to two different groups of animals,respectively, over a period of 28 days.A third(control) group of animals received distilled water only,orally over the same period.Five animals from each of the groups were sacrificed on day 8,15 and 29.Venous blood samples and reproductive organs respectively were taken from each group of sacrificed animals for hormonal and histopathological analysis.Results:Results of the hormonal assay revealed a general increase in the levels of Follicle Stimulating Hormone(FSH),Luteinizing Hormone(LH),progesterone,and estrogen.The highest levels were noticed in the animals sacrificed on the 29th day(LH =5.48±0.04 IU/L;FSH =3.80±0.00 IU/ L;Progesterone =7.14±0.15 nmol/L;Estrogen = 0.168±0.002 nmol/L).These increases were statistically significant compared to those of the control animals(LH =2.90±0.00 IU /L;FSH = 1.28±0.02 IU/L; Progesterone = 3.80±0.00 nmol/L;Estrogen = 0.130±0.002 nmol/L;P【0.05),and were also dose dependent. Results of the histopathological studies showed presence of chronic inflammatory cells in the tissues of the fallopian tubes and uterus on the 29th day.However,no changes were observed in the ovaries.Conclusion: The administration of the extract produced a dose and time-dependent increase in FSH,LH,progesterone and estrogen levels.We postulate that these observed effects may have been induced by the phytoestrogens (known to have 1/1 000 th of the efficacy of natural oestrogens) in the extract.The hormonal and histopathological changes may explain the effects described by patients following ingestion of extracts of this plant in traditional medical practice.However,it remains to be determined if these effects are harmful or beneficial in disease conditions.
文摘CeO 2 improves the activity and selectivity of Pd/Al 2O 3 catalyst for methanol decomposition. The interaction between Pd and CeO 2 was then proposed to result in the promoting effect. The selectivity of CO and H 2 is significantly improved by addition of La 2O 3 to either Pd/Al 2O 3 or Pd/CeO 2/Al 2O 3 catalysts. Moreover, a synergistic promotion between CeO 2 and La 2O 3 on γ Al 2O 3 supported Pd catalysts was observed for the catalytic activity towards methanol decomposition into CO and H 2.
基金the Ministry of Higher Education Malaysia for providing financial support to this work via FRGS No:FRGS/1/2011/SG/UTP/02/13Universiti Teknologi PETRONAS
文摘A series of novel carbon nanofibers(CNFs)based Cu-ZrO2 catalysts were synthesized by deposition precipitation method.To investigate the influence of promoter,catalysts were loaded with 1,2,3 and 4 wt%ZnO and characterized by ICP-OES,HRTEM,BET,N2O chemisorption,TPR,XPS and CO2-TPD techniques.The results revealed that physicochemical properties of the catalysts were strongly influenced by incorporation of ZnO to the parent catalyst.Copper surface area(SCu)and dispersion(DCu)were slightly decreased by incorporation of ZnO promoter.Nevertheless,SCuand DCuwere remarkably decreased when ZnO content was exceeded beyond 3 wt%.The catalytic performance was evaluated by using autoclave slurry reactor at a pressure and temperature of 30 bar and 180℃,respectively.The promotion of CuZrO2/CNFs catalyst with 3 wt%of ZnO enhanced methanol synthesis rate from 32 to 45 g kg^-1 h^-1.Notably,with the ZnO promotion the selectivity to methanol was enhanced to 92%compared to 78%of the un-promoted Cu-ZrO2/CNFs catalyst at the expense of a lowered CO2 conversion.In addition,the catalytic activity of this novel catalyst system for CO2 hydrogenation to methanol was compared with the recent literature data.
基金supported by the National Natural Science Foundation of China (Nos. 61675143, 11661131002)the Natural Science Foundation of Jiangsu Province (No. BK20160277)+2 种基金the Soochow University-Western University Joint Centre for Synchrotron Radiation Researchthe Collaborative Innovation Center of Suzhou Nano Science & Technologythe Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘We present a straightforward physical approach for synthesizing multiwalled carbon nanotubes(CNTs)-Pd Au/Pt trimetallic nanoparticles(NPs), which allows predesign and control of the metal compositional ratio by simply adjusting the sputtering targets and conditions. The small-sized CNTs-Pd Au/Pt NPs(~3 nm, Pd/Au/Pt ratio of 3:1:2) act as nanocatalysts for the methanol oxidationreaction(MOR), showing excellent performance with electrocatalytic peak current of 4.4 A mg^(-1) Pt and high stability over 7000 s. The electrocatalytic activity and stability of the Pd Au/Pt trimetallic NPs are much superior to those of the corresponding Pd/Pt and Au/Pt bimetallic NPs,as well as a commercial Pt/C catalyst. Systematic investigation of the microscopic, crystalline, and electronic structure of the Pd Au/Pt NPs reveals alloying and charge redistribution in the Pd Au/Pt NPs, which are responsible for the promotion of the electrocatalytic performance.
基金Supported by the 973 Program of the Ministry of Science and Technology of China(No. 2003CB615800)the NationalNatural Science Foundation of China(No. 29973041).
文摘A catalytic reaction over a silver catalyst performed in an unregarded temperature region（473-873 K） with a long catalytic lifetime for the production of methyl formate from methanol was provided as a potential preparing route. The optimal yield of methyl formate（ca. 14. 8% ） with a selectivity 〉90% was obtained at about 573 K. Because α- oxygen species and bulk oxygen species coexist in the unregarded temperature region, a synergistic process concerning α-oxygen species and bulk oxygen species was proved over Oα -rich and Oγ-rich samples.
