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1.
Guilin Zhou Tian Wu Haibing Zhang Hongmei Xie Yongcheng Feng 《Chemical Engineering Communications》2013,200(2):233-240
Mesoporous Co/KIT-6 and Co/SiO2 catalysts were prepared via hydrogen reduction and were subsequently used in CO2 catalytic hydrogenation to produce methane. The properties of the prepared Co/KIT-6 catalyst were investigated by low-angle X-ray diffraction, Brunauer-Emmett-Teller analysis, and transmission electron microscopy. The results indicate that the synthesized Co/KIT-6 catalyst has mesoporous structures with well-dispersed Co species, as well as higher CO2 catalytic hydrogenation activities than that of the Co/SiO2 catalyst. The Co/KIT-6 catalyst has a large specific surface area (368.9 m2 · g?1) and a highly ordered bicontinuous mesoporous structure. This catalyst exhibits excellent CO2 catalytic hydrogenation activity and methane product selectivity; the CO2 conversion and methane selectivity of the Co/KIT-6 catalyst at 280°C are 48.9% and 100%, respectively. The highly ordered, bicontinuous mesoporous structure of the Co/KIT-6 catalyst improves selectivity for the methane product. 相似文献
2.
Copper oxide doped mesoporous KIT-6 materials were synthesized by ultrasonication as impregnation method. The highly ordered nature of mesoporous CuO-KIT-6 materials analyzed by low angle X-ray diffraction. The high surface area, pore diameter and mesoporous nature of synthesized materials were confirmed by BET surface area analysis. Si–O–Si, Si–OH and Cu–O–Si bonds in the framework of CuO-KIT-6 were verified by FTIR spectroscopy. The Cu2+ ← O2? charge-transfer transitions and d–d transitions of dispersed Cu2+ on ordered mesoporous KIT-6 were identified by DRS UV–Vis spectroscopy. The morphology of the synthesized CuO-KIT-6 materials was analyzed by HR-SEM. The 3D ordered nature of CuO-KIT-6 confirmed by TEM analysis. The highly ordered 3D mesoporous CuO-KIT-6 materials are excellent catalyst for benzene hydroxylation reaction through C-H activation and styrene epoxidation reaction with 30 % aqueous H2O2. The catalyst CuO-KIT-6 itself showed a good conversion towards both reactions. 相似文献
3.
Alaa Fahmy Karam S. El-Nasser Ibraheem O. Ali Tarek M. Salama Korinna Altmann 《Journal of Adhesion Science and Technology》2013,27(24):2641-2656
The electrospray ionization (ESI) method was used for deposition of thin films of poly(acrylic acid) (PAA) on Cu/ZSM-5 (5 wt.% Cu) and Ag–Cu/ZSM-5 (1 wt.% Ag and 4 wt.% Cu) composites. For comparative purposes, the ZSM-5 zeolite was synthesized under hydrothermal conditions and loaded with PAA under the same treating conditions as the composites. This method allowed the formation of uniform polymer films of controlled thickness on conductive substrates. The structural characteristics were characterized by X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, atomic force microscopy and X-ray diffraction (XRD). The deposited PAA layer over ZSM-5 acts as a common dispersing and stabilizing agent through coordination-driven guest-templated polymer via interaction of Ag+ and Cu2+ with carboxylic acid groups, thus increasing and controlling the adhesion and the release of metallic species. A short exposure to light and temperature has reduced the metal ions to Cu0 and Ag0 metallic nanoparticles. The results of XRD analysis let suggest that the interaction of Cu and Ag with carboxylic groups of PAA inhibits the formation of large metallic silver particles. These samples were being studied for their potential as antibacterial agents toward the bacterial strains such as Staphylococcus pneumonia, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa as Gram positive and Gram negative bacteria, respectively. Aspergillus fumigatus and Candida albicans as Fungi were also evaluated. The Cu/ZSM-5 and Ag–Cu/ZSM-5 nanocomposites coated with a 10 nm thick PAA layer exhibit significant antibacterial activity. 相似文献
4.
S. Narayanan J. Judith Vijaya S. Sivasanker L. John Kennedy A. Ariharan 《Journal of Porous Materials》2014,21(5):633-641
In the present paper, nanocrystalline hierarchical ZSM-5 zeolites were successfully synthesized by the hydrothermal method in the presence of tetrapropylammonium hydroxide as a single template with the gel composition of 58SiO2:Al2O3:20TPAOH:1,500H2O. The prepared zeolite catalysts were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Nitrogen adsorption–desorption (BET), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HR-TEM) techniques. The formation of pure and highly crystalline ZSM-5 zeolite phase is confirmed by XRD. The IR vibration band at 550 cm?1 is assigned to the double 5-rings of MFI-type zeolites. N2 adsorption–desorption isotherms showed that the synthesized product had high BET surface area and possessed composite pore structures with both micro and mesopores. The catalytic performance of hierarchical ZSM-5 zeolite was investigated in the selective oxidation of benzyl alcohol (BzOH) with hydrogen peroxide (H2O2) under mild conditions. The results showed that the conversion of BzOH and the selectivity to benzaldehyde were about 94 and about 99 % respectively, when using 0.08 g ZSM-5 catalyst with acetonitrile as the solvent and H2O2 as the oxidant at 90 °C. This catalyst can be retrieved and reprocessed for five times without a significant loss in its activity and selectivity. 相似文献
5.
《Applied catalysis》1983,5(1):109-117
The nature of pentasil zeolites synthesized in specific conditions by using various tetraalkylammonium (Al k4N+) cations or the corresponding trialkylamine (A1k3N) precursors was investigated.ZSM-8, ZSM-5 and ZSM-11 zeolites are obtained using tetraethylammonium (Et4N+) tetrapropylammonium (Pr4N+) and tetrabutyl ammonium (BU4N+) bromide respectively, demonstrating the structure-directing role of the A1k4N+ cation. TG data suggest that the organic molecules fill completely the channel system in all cases.When trialkylamines are used as organic bases, intermediate ZSM-5/ZSM-11 phases are obtained. A ZSM-5-rich phase is formed in the presence of tributylamine (Bu3N) whilst the use of tripropylamine (Pr3N) yields a ZSM-11-rich phase. The nature of the mixed phases seems to be determined more by the zeolite channel filling than by the location of the organic molecules at the channel intersections.By using Pr3N and n-propylbromide (PrBr), a pure ZSM-5 phase is obtained although the chemical species occluded within the zeolite is identified as Pr3N by high resolution solid state NMR spectroscopy. This suggests that the structure-directing effect in the system (Pr3N + PrBr) is that of Pr4N+ cations formed in traces, which operates only at the nucleation stages of the synthesis. 相似文献
6.
A series of Fe3+ containing catalysts were synthesized using ion-exchange technique over hierarchically porous ZSM-5 (M-ZSM-5) and micro-mesoporous composite ZSM-5/MCM-41 (ZSM-5/MCM-41), respectively. The prepared catalysts were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope, N2 adsorption–desorption, UV–Vis spectroscopy, temperature programmed reduction and inductively coupled plasma-optical emission spectroscopy. The characterization results exhibit that the hierarchically porous ZSM-5 was synthesized with intracrystalline mesopores, while the micro-mesoporous composite ZSM-5/MCM-41 was prepared with the well-ordered mesopores. Furthermore, the results also prove that the existence of iron in the catalysts was mainly presented in the form of Fe3+ ions. Catalytic performances of the samples for phenol hydroxylation were compared by using H2O2 as oxidant. Under the optimized conditions, Fe3+ ion-exchanged M-ZSM-5 (Fe-M-ZSM-5) shows that a phenol conversion of 42.3% obtained with 92.5% selectivity to dihydroxybenzenes, whereas Fe3+ ion-exchanged ZSM-5/MCM-41 (Fe-ZSM-5/MCM-41) give 46.2% phenol conversion and 90.1% dihydroxybenzenes selectivity, which are all better than most reported results. The recyclability tests show that Fe-ZSM-5/MCM-41 with ordered mesoporous structure and bigger surface area has better anti-deactivation performance than Fe-M-ZSM-5. The excellent catalytic performances were due to the improved diffusion performance with newly created mesopores and the highly active Fe3+ species obtained by ion-exchange technique. 相似文献
7.
LiFePO4/C and LiFe0.96Pt0.04PO4/C nanocomposite cathode materials were synthesized using the sol–gel method in a nitrogen atmosphere. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Their electrochemical properties were investigated using galvanostatic charge/discharge tests, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The XRD results indicate that substituting iron with platinum does not destroy the structure of LiFePO4, but expands the lattice parameters and enlarges the cell volume. The electrochemical results show that platinum doping improves the electrochemical performance of LiFePO4/C particles owing to the expansion of the lattice structure, which provides more space for Li ion diffusion. The, larger lattice structure parameters of the LiFe0.96Pt0.04PO4/C material result in a high discharge capacity of 166, 156, 142 and 140 mAh g?1 at rates of 0.2, 1, 5, and 10 C, respectively, as compared to 164, 150, 120, and 105 mAh g?1 for undoped LiFePO4/C. 相似文献
8.
Snehalkumar Parmar Kamal K. Pant Mathew John Kishore Kumar Shivanand M. Pai Shalini Gupta Bharat L. Newalkar 《Journal of Porous Materials》2014,21(5):849-857
Hydroisomerization of n-hexadecane is performed over ZSM-12 framework having tailored Brønsted acidity to investigate the effect in terms of product selectivity and yield. For this purpose, pure phase of ZSM-12 (bulk molar ratio Si/Al ~ 60) has been synthesized using TEABr as a structure directing agent. The framework Brønsted acidity is tailored with group II elements (M) viz. Ca, Ba and Mg, by means of ion-exchange method. The samples so prepared have been characterized for phase purity, textural parameters, morphology by employing powder X-ray diffraction, nitrogen adsorption–desorption isotherm measurement at 77 K, and scanning electron microscopy technique, respectively. Similarly, % metal exchange is estimated using inductively coupled plasma technique. The quantification of Brønsted acidity for H+–M++–ZSM-12 samples has been estimated by means of ammonia temperature programmed desorption (NH3-TPD) and Fourier transform infrared spectroscopy of ammonia (NH3-FTIR). The well characterized H+–M++–ZSM-12 samples were loaded with Platinum (Pt, 0.5 wt%) and subjected to hydroisomerization of n-hexadecane using an up-flow fixed bed reactor to verify the effect of process parameters like temperature and WHSV. Pt/H+–Ba2+–ZSM-12 with tailored Brønsted acidity in the range of about 25 % demonstrated the optimum performance among all the catalysts with an increased isomer selectivity and yield (89.2 and 80.3 %, respectively) by about 4 wt% at a conversion level of about 90 % compared to Pt/H+–ZSM-12 framework at 568 K. Such enhancement in isomer selectivity and yield is found to be significant from commercial application point of view. Based on the obtained trend, the potential benefits of implementation of Pt/H+–Ba2+–ZSM-12 (bulk molar ratio Si/Al ~ 60) framework for cold flow property improvement of ‘bio-ATF’ have been envisaged. 相似文献
9.
Mesoporous aluminosilicates (Al-MCM-41) with high hydrothermal stability were synthesized via self-assembly of nanoseed precursors, obtained from alkali-treatment of ZSM-5. Characterized by N2 sorption, Transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and Mercury intrusion, as-prepared Al-MCM-41 possessed a large number of void defects, enhancing the connectivity of MCM-41. The effects of alkali-treatment degree, including time and concentration, on volume of void defects were investigated and discussed. It is revealed that volume of void defects decreased in the severe condition of alkali-treatment, and void defects representing the intraparticular pores account for a volume of 0.138 cm3/g in Al-MCM-41, prepared under the condition of 1.0 mol/L of NaOH and 1 h of stirring time. A tentative proposed mechanism for interpreting the formation of void defects was presented. Aggregated secondary building units in the precursors not only provided Si (Al) sources, but also functioned as templates for the development of void defects. Al-MCM-41 with void defects would be beneficial to diffusion and mass transportation. 相似文献
10.
Yunsheng Xia Yue Zhao Yuzhen Li Fengyun Hu Lan Zhang Wenjun Chen 《Journal of Porous Materials》2016,23(6):1591-1595
Three-dimensional (3D) ordered mesoporous samarium oxides with cubic polycrystalline structure were fabricated by means of vacuum-assisted impregnation and mill impregnation route using ordered mesoporous SiO2 (KIT-6) as the hard template with nitrate samarium as the metal source. The structure and morphology of the as-prepared materials were characterized by XRD, TEM and N2 adsoption-desorption. It is found that the mesoporous Sm2O3 sample obtained by vacuum-assisted method have a higher surface area (184 m2 g?1) than that (142 m2 g?1) of mill impregnation and had a better 3D mesoprosity, which has potential applications in the catalytic reaction. 相似文献
11.
This report covered some new contributions in catalyst preparation and characterization. Meso-structured silica–calcium mixed oxide catalyst possessed both acidic and basic sites was synthesized through co-condensation method in alkaline environment using tetraethylorthosilicate, CaO, and cetyltrimethylammoniumbromide. The co-condensation process was established at 90 °C for 24 h obtaining white-gel precipitate which was dried at 120 °C followed by calcination at 550 °C for 5 h. The as-synthesized catalyst was used in conversion of rich free fatty acid rubber seed oil (22 %wt) in Vietnam to fatty acid methyl esters (FAMEs) in mild conditions such as temperature of 120 °C, time of 4 h, catalyst dosage of 3 %wt, methanol/oil mass ratio of 2.5/1 and agitating speed of 550 rpm achieving the reaction yield of 95.4 %. The catalyst were characterized by various techniques such as X-ray diffraction, transmission electron spectroscopy, Nitrogen Adsorption–Desorption Analysis (BET), temperature programmed desorption (NH3 and CO2-TPD). Especially, X-ray absorption spectroscopies was applied to explain the occurrence of acid and base sites on catalysts surface. The analysis showed the sixfold coordinated calcium sites characterizing for the mixed oxide structure of CaO–SiO2. The results helped to simulate the bonding structure around the Ca sites indicating the electrostatic charge differences along the Ca–O–Si connections and the ability for occurring the defect sites containing the O2? moieties corresponding to the acidity and basicity of the catalysts respectively. Gas chromatography–mass spectroscopy was also used to determine the composition of the FAMEs showing high purity of these products. 相似文献
12.
Hong-Xia Cao Jun Zhang Xiang-Kun Ren Cheng-Long Guo 《Korean Journal of Chemical Engineering》2017,34(9):2374-2382
Ni-based catalysts supported on a support with 3D-mesopores, including Ni/KIT-6(EG), Ni/KIT-6(PS) and Ni/KIT-6(DS), were prepared by adding ethylene glycol, direct synthesis and post synthesis methods, respectively, and their catalytic properties were investigated for CO methanation as one of the core technologies of synthetic natural gas production in a continuous flow fixed-bed reactor. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDS), hydrogen temperature-programmed reduction (H2-TPR), hydrogen temperature-programmed desorption (H2-TPD) and thermal gravimetric analysis (TGA), respectively. The results showed that Ni/KIT-6(EG) exhibited the best catalytic performance with CO conversion of almost 100% and CH4 yield of 75% at 450 °C, atmospheric pressure and 60,000 mL/g/h due to the higher dispersion of Ni species, stronger reducibility of NiO and formation of smaller Ni nanoparticles fixed into 3D-mesopores, indicating that adding ethylene glycol was effective to improve catalytic performance of Ni-based catalyst for CO methanation. Moreover, compared with Ni/Al2O3(EG) prepared using Al2O3 as a support, Ni/KIT-6(EG) showed better catalytic performance owing to the higher specific surface area, stronger reducibility of NiO and confinement effect of 3D-mesopores promoting to produce more active sites. After 60h lifetime test of Ni/KIT-6(EG) at 500 °C, atmospheric pressure and 60,000 mL/g/h, 3D-mesopores were still maintained and no obvious agglomeration of Ni nanoparticles was observed, meaning that Ni species were still well dispersed into 3D-mesopores. As a consequence, Ni/KIT-6(EG) exhibited superior catalytic performance and stability, which makes it a promising candidate for CO methanation. 相似文献
13.
Adsorption isotherms of carbon dioxide were measured on six high-silica zeolites TNU-9, IM-5, SSZ-74, ferrierite, ZSM-5 and ZSM-11 comprising three-dimensional 10-ring (8-ring for ferrierite) at 273, 293, 313 and 333 K. Based on the known temperature dependence of CO2 adsorption, isosteric heats of adsorption were calculated. The obtained adsorption capacities and isosteric adsorption heats related to the amount of CO2 adsorbed have provided detailed insight into the carbon dioxide interaction with zeolites of different framework topology. The zeolites TNU-9 and ferrierite are characterized by pronounced energetic heterogeneity whereas due to the location of Na+ cations in the same positions the isosteric adsorption heats of CO2 adsorption on IM-5, ZSM-5 and ZSM-11 zeolites are rather constant for molecular ratio CO2/Na+ < 1. As IM-5 zeolite has a maximum adsorption capacity, it appears to have optimum properties for carbon dioxide separation. 相似文献
14.
Asunción Aranda Begoña Puértolas Benjamín Solsona Said Agouram Ramón Murillo Ana María Mastral Stuart H. Taylor Tomas Garcia 《Catalysis Letters》2010,134(1-2):110-117
Ceria catalysts have been prepared by a nanocasting procedure using SBA-15, MCM-48 and KIT-6 silica-based templates, and investigated for the total oxidation of naphthalene. In all cases cubic fluorite CeO2 was prepared, and the structure of the template was replicated when SBA-15 and MCM-48 were used. The KIT-6 template was not replicated by the nanocasting synthesis, but in all cases mesoporous CeO2 was obtained with high surface areas (91–190 m2 g?1). All of the catalysts demonstrated high activity for naphthalene oxidation to CO2, and the most active was the catalyst prepared from the KIT-6 template. The high activity was attributed to the small crystallite size of the CeO2, combined with high surface area and the highly accessible catalyst surface. 相似文献
15.
Fabrication and characterization of high energy density supercapacitor based on graphite oxide/polypyrrole (GO/PPy) composites is reported. Improvement in charge storage has been obtained by exfoliation of graphite oxide sheets via intercalation of polypyrrole. The formation of composite has been shown by the analysis of X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and Fourier transfer of infrared spectroscopy data. Scanning electron and transmission electron microscopy clearly show sheet-like layered structure of graphite oxide surrounded by polypyrrole. Supercapacitors fabricated using this composite system result in a reduced equivalent series resistance value ~1.85 Ω. Such low value can be attributed to the intercalation of conducting polypyrrole into the graphite sheets. A specific capacitance of ~181 F g?1 in 1 M Na2SO4 aqueous electrolyte with a corresponding specific energy density of ~56.5 Wh kg?1 could be achieved. These values make GO-based materials suitable for their use as electrodes in high performance supercapacitors. 相似文献
16.
Dipak B. Shukla Vyomesh P. Pandya 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1989,44(2):147-154
A fast and accurate method for identification and determination of purity of Zeolite Socony Mobil 5 (ZSM-5) zeolite was developed using the IR optical density ratio of the bands at 550 and 450 cm?1 in the mid-IR region of the structure spectra. The optical density values obtained from the proposed method, for ZSM-5 zeolite synthesized, are compared with those of the Bayer ZSM-5 zeolite used as reference material. For well-crystallized calcined ZSM-5 zeolite, this ratio is circa 0.8. This ratio is found to be less, if amorphous silicate is present in zeolite. The presence of a band at 550 cmSUP>?1 in addition to the one at 450 cm?1 shows that ZSM-5 zeolite has been formed even if the material is X-ray amorphous. The absence of the structure-sensitive band at 550 cm?1 unambiguously indicates that such a zeolite has not been formed. 相似文献
17.
M. Jason Kelly Jaehoon Kim George W. Roberts H. Henry Lamb 《Topics in Catalysis》2008,49(3-4):178-186
A series of Pd/γ-Al2O3 catalysts was prepared from [Pd(hfac)2] (hfac = hexafluoroacetylacetonate) in liquid carbon dioxide using the method reported by Kim et al. [Chem Mater 18:4710 (2006)]. The catalysts were characterized using CO pulse chemisorption, diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray absorption fine structure (XAFS) spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron microscopy. The catalysts were reduced initially in the high-pressure CO2 reaction cell using H2 at 75 °C. Samples were removed, stored in a desiccator, and re-reduced in situ at 250 °C prior to pulse chemisorption, DRIFTS and XAFS. CO pulse chemisorption evidenced that the Pd dispersion decreased from 55% to 5% as the Pd loading increased from 0.58 to 3.94 wt.%. The as-prepared 0.58 and 1.77 wt.% Pd/γ-Al2O3 catalysts (after air exposure) contained oxidized Pd species that were converted after in situ reduction to supported Pd particles. The average Pd particle sizes of these two catalysts (16 and 23 Å, respectively) estimated from the first-shell Pd–Pd coordination numbers are in good agreement with the CO chemisorption results. DRIFTS evidenced a prevalence of weakly bound linear CO (νCO = 2083 cm?1) adsorbed on the 0.58 wt.% Pd catalyst. A 2.95 wt% Pd catalyst (49 Å average particle size) also exhibited a strong linear CO band (νCO = 2093 cm?1). In contrast, CO chemisorption on a commercial 1 wt.% Pd/Al2O3 catalyst (37 Å average particle size) gave predominantly 2-fold bridging CO species. We infer that the supported Pd particles prepared from [Pd(hfac)2] are rougher on the atomic scale (with a higher percentage of edge and corner atoms) than equivalently sized particles in conventionally prepared Pd/γ-Al2O3 catalysts. 相似文献
18.
Nia Richards Ewa Nowicka James H. Carter David J. Morgan Nicholas F. Dummer Stanislaw Golunski Graham J. Hutchings 《Topics in Catalysis》2018,61(18-19):1983-1992
The influence of Fe speciation on the decomposition rates of N2O over Fe–ZSM-5 catalysts prepared by Chemical Vapour Impregnation were investigated. Various weight loadings of Fe–ZSM-5 catalysts were prepared from the parent zeolite H-ZSM-5 with a Si:Al ratio of 23 or 30. The effect of Si:Al ratio and Fe weight loading was initially investigated before focussing on a single weight loading and the effects of acid washing on catalyst activity and iron speciation. UV/Vis spectroscopy, surface area analysis, XPS and ICP-OES of the acid washed catalysts indicated a reduction of ca. 60% of Fe loading when compared to the parent catalyst with a 0.4 wt% Fe loading. The TOF of N2O decomposition at 600 °C improved to 3.99?×?103 s?1 over the acid washed catalyst which had a weight loading of 0.16%, in contrast, the parent catalyst had a TOF of 1.60?×?103 s?1. Propane was added to the gas stream to act as a reductant and remove any inhibiting oxygen species that remain on the surface of the catalyst. Comparison of catalysts with relatively high and low Fe loadings achieved comparable levels of N2O decomposition when propane is present. When only N2O is present, low metal loading Fe–ZSM-5 catalysts are not capable of achieving high conversions due to the low proximity of active framework Fe3+ ions and extra-framework ɑ-Fe species, which limits oxygen desorption. Acid washing extracts Fe from these active sites and deposits it on the surface of the catalyst as FexOy, leading to a drop in activity. The Fe species present in the catalyst were identified using UV/Vis spectroscopy and speculate on the active species. We consider high loadings of Fe do not lead to an active catalyst when propane is present due to the formation of FexOy nanoparticles and clusters during catalyst preparation. These are inactive species which lead to a decrease in overall efficiency of the Fe ions and consequentially a lower TOF. 相似文献
19.
Carbon nanotubes/amorphous carbon composites as high-power negative electrodes in lithium ion capacitors 总被引:1,自引:0,他引:1
A nitrogen-rich carbon nanotubes/amorphous carbon (CNT/C) composite was prepared by carbonising a CNT/polyaniline (PANI) composite, and characterised. Scanning electron microscopy and X-ray photoelectron spectroscopy confirmed that the composite retained a mesoporous CNT structure as its backbone, whilst the nitrogen-rich PANI-derived carbon formed a thin amorphous coating on the CNT surface. Electrochemical characterisation of the CNT/C composite indicated that it had nearly double the reversible Li+ intercalation capacity (390 vs. 219 mAh g?1) and 39 % less irreversible capacity (622 vs. 1,015 mAh g?1) than the pristine CNT. The CNT/C composite showed exceptionally high rate capability with a de-intercalation capacity of 81 mAh g?1 at a very high charge/discharge rate of 60 C (time taken for charge or discharge is 1 min) (1 C = 1 h charge or discharge), whereas the pristine CNT delivered 53 mAh g?1 at this C-rate. By comparison, the rate capabilities of conventional graphite (N3 and SLP30) were very poor above 5 C (~17 mAh g?1 at 5 C). Both the pristine CNT and CNT/C composite showed an excellent cyclability at 1 C charge/discharge over 600 cycles. The CNT/C composite maintained a fairly stable capacity of ~200 mAh g?1 after 600 cycles, whilst the commercial graphite showed a steady and significant decrease in de-intercalation capacity; reaching <70 mAh g?1 after 600 cycles. 相似文献
20.
Ali Dehghani Maryam Ranjbar Ali Eliassi 《Journal of Inorganic and Organometallic Polymers and Materials》2018,28(3):585-593
In this study, Cu/Zn/Al2O3-AC (AC?=?activated carbon) catalyst was synthesized and evaluated for dimethoxymethane (DMM) reformation to hydrogen. The Cu/Zn/Al2O3-AC catalyst was prepared using high surface area metal organic frameworks (MOFs) consisting of Cu3(BTC)2 (MOF-199) and Zn4O(BDC)3 (MOF-5) for Cu(II) and Zn(II) sources respectively, as precursors while γ-Al2O3 was applied as support. The synthesized catalyst was investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Brunauer–Emmett–Teller analysis (BET), Temperature programmed desorption (NH3-TPD) and Energy-dispersive X-ray spectroscopy (EDX) techniques. Complete DMM conversion was observed over Cu/Zn/Al2O3-AC catalyst (Cu:Zn:Al mole ratio of 6:3:2) under atmospheric pressure, T?=?533 K, GHSV?=?20 NL h?1 gcat?1, N2/H2O/DMM?=?24/5/1 volume percent (vol%) with hydrogen productivity of 12.8 L H2 h?1 gcat?1 and 64% hydrogen concentration. Application of MOFs as precursors and modified activated carbon as an acidic component provided the catalyst with the porous structure and high specific surface area for the hydrolysis of DMM, subsequently, high selectivity and productivity of hydrogen was obtained. 相似文献