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1.
The composite nanomaterial of Pd-La(OH)3/C was successfully synthesized via intermittent microwave heating–glycol reduction method and characterized with X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. The TEM photograph shows that Pd-La(OH)3 is well polymerized and dispersed on the carbon support. The performance of the prepared material for ethanol oxidation was evaluated by cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and chronopotentiometry (CP) measurements in alkaline media. The results reveal that Pd-La(OH)3/C has significantly higher activity and stability than that of Pd/C with the same Pd loading of 0.1 mg cm?2. The stable potential reaches to ?0.38 V vs. Hg/HgO at 20 mA cm?2 on the Pd-La(OH)3/C electrode in CP curve. Single direct ethanol fuel cell (DEFC) was constructed using Pd-La(OH)3/C electrode and MnO2/C electrode as the ethanol anode and air cathode respectively, where the cell voltage can stay at 0.4 V under the current density of 20 mA cm?2 by discharge test at room temperature.  相似文献   

2.
Electrochemical depositions of hybrid polypyrrole/nickel cobalt oxide (PPy/NiCoO) coatings onto ferritic stainless steel surface were carried out with different electrochemical techniques from 0.1 M pyrrole (Py) in 0.2-M oxalic acid (OA) solution and less than 150-nanometer-sized NiCoO particles. The structural properties of the composite were investigated by using different methods such as transmission electron microscopy (TEM), scanning electron microscopy (SEM) with energy-dispersive X-ray spectrometer (EDS) and Raman spectroscopy. The embedded NiCoO particles, uniformly distributed onto the surface of the PPy film, have similar oxide ratios corresponding to a mixed oxide structure. The electrochemical characterization was done using polarization curves and linear sweep voltammetry (LSV) related to oxygen reduction reaction (ORR) in alkaline solution and hydrogen peroxide as an oxygen source. Concerning the exchange current densities for ORR, the obtained values (between 1.06 and 1.45?×?10?3 mA cm?2 for a total amount of NiCoO of 0.1 mg cm?2) are comparable with other polymer films with Pt.  相似文献   

3.
In this work, green synthesis of cobalt doped titanium dioxide (Co‐TiO2) has been carried out in aqueous medium using gelatin. The Co‐TiO2 particles have been characterized using transmission electron microscopy (TEM), X‐ray diffraction (XRD), energy dispersive X‐ray (EDAX), FT‐IR spectroscopy and voltammetry techniques. XRD results show pure Co‐TiO2 and TiO2 powders with average crystallite size about 12 nm and 15 nm, respectively. Co loaded in TiO2 hasn't influence crystalline structure. Moreover, efficient Co‐TiO2‐based anode was fabricated by casting of the Co‐TiO2 solution on glassy carbon electrode (Co‐TiO2/GCE). The electrocatalysis of oxygen evolution reaction (OER) at Co‐TiO2/GCE has been examined using linear scanning voltammetry (LSV) in alkaline media. The OER is significantly enhanced at Co‐TiO2/GCE, as demonstrated by a negative shift in the LSV curve at the Co‐TiO2/GCE compared to that obtained at the unmodified one. The value of energy saving of oxygen gas at a current density of 5 mA cm?2 is 12.6 kW h kg?1. The low cost as well as the marked stability of the modified electrode make it promising candidate in industrial water electrolysis process.  相似文献   

4.
A composite comprised of oxygen reduction reaction (ORR) catalyst and oxygen evolution reaction (OER) catalyst was designed and applied as a bifunctional electrocatalyst for the air electrode of the lithium-air battery. The ordered mesoporous carbon nitride (MCN) prepared by a nano hard-templating approach displayed a surface area as high as 648 m2 g?1 and a large pore volume of 0.7 cm3 g?1 and acted as both the ORR catalyst and the support for the in situ-formed OER catalyst of Pt particles with a diameter of 3–4 nm. The electrochemical performances of the electrode were examined in a solid-state lithium-air cell structured as Li/LATP-based electrolyte/cathode, which demonstrated a higher round-trip efficiency and lower overpotential compared with the Pt@AB and MCN electrodes. The combination of the OER and ORR catalysts is proved as an effective way to improve the performance of lithium-air batteries.  相似文献   

5.
Hierarchical porous carbons (HPCs) with abundant mesopores have been prepared by a facile route from the starch that was pretreated by calcium acetate. The scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and N2 adsorption–desorption tests show that hierarchical porous carbons with bimodal mesopores have been obtained. Moreover, the pore sizes are tunable by simply adjusting the reactants ratio and carbonization temperature. The as-synthesized hierarchical porous carbon materials (HPCs-2-800) possesses the highest Brunauer-Emmett-Teller (BET)-specific surface area of 464 m2 g?1 and mesoporous volume of 0.663 cm3 g?1 at the carbonization temperature of 800 °C and starch to calcium acetate mass ratio of 2. Electrochemical measurements also display that the HPCs-2-800 electrodes have a high reversible capacity of 244 F g?1 at the current density of 0.1 A g?1 and 182 F g?1 at the current density of 10 A g?1. When the current density is elevated from 0.1 to 10 A g?1, the high capacitance retention of 74.6 % reveals a good rate performance. Long charge–discharge cycling measurements disclose good stabilities over 25,000 cycles at different current densities of 1–10 A g?1 (5000 cycles at each current density) for HPCs-2-800 electrode. The cycling results indicate a high capacitance retention of 99.6 % over 5000 charge–discharge cycles even at the current density of 10 A g?1. The excellent supercapacitive performances imply that HPCs-2-800 is a promising candidate for supercapacitors.  相似文献   

6.
Carbon-supported Ni@Ag core-shell nanoparticles were synthesized and used as the anode electrocatalyst for direct borohydride-hydrogen peroxide fuel cell (DBHFC). The morphology, structure, and composition of the as-prepared electrocatalysts are characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). Electrochemical characterizations are performed by cyclic voltammetry (CV), chronoamperometry (CA), linear scan voltammetry with rotating disk electrode (LSV RDE), and fuel cell test. The catalytic behaviors and main kinetic parameters (e.g., Tafel slope, number of electrons exchanged, exchange current density, and apparent activation energy) toward BH 4 oxidation on Ag/C and Ni@Ag/C electrocatalysts are determined. Results show that the as-prepared nanoparticles have a core-shell structure with the average size approximately 13 nm. The kinetics of NaBH4 oxidation is faster for Ni@Ag/C than that for Ag/C. Among the as-prepared catalysts, the highest transition electron value and the lowest apparent activation energy are obtained on Ni1@Ag1/C; the values are 4.8 and 20.23 kJ mol?1, respectively. The DBHFC using Ni1@Ag1/C as anode electrocatalyst and Pt mesh (1 cm2) as cathode electrode obtains the maximum anodic power density as high as 8.54 mW cm?2 at a discharge current density of 8.42 mA cm?2 at 25 °C.  相似文献   

7.
Multiwalled carbon nanotube (MWCNT)–vanadium pentoxide (V2O5) nanocomposites have been fabricated using a facile and environmental friendly hydrothermal method without any pretreatment, surfactants, or chelate agents added. The as-annealed nanocomposites are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and the results indicate that V2O5 nanoparticles grew on MWCNTs. As a cathode material for lithium batteries, it exhibits superior electrochemical performance compare to the pure V2O5 powders. A high specific discharge capacity of 253 mA h g?1 can be obtained for the 15 % MWCNT–V2O5 nanocomposite electrodes, which retains 209 mA h g?1 after 50 cycles. However, the pure V2O5 powder electrodes only possess a specific discharge capacity of 157 mA h g?1 with a capacity retention of 127 mA h g?1 after 50 cycles. Moreover, the MWCNT–V2O5 nanocomposite electrodes show an excellent rate capability with a specific discharge capacity of 180 mA h g?1 at the current rate of 4 C. The enhanced electrochemical performance of the nanocomposites is attributed to the formation of conductive networks by MWCNTs, and large surface areas of V2O5 nanoparticles grew on MWCNTs which stabilizes these nanoparticles against agglomeration.  相似文献   

8.
Tungsten carbide and graphitic carbon (WC/GC) composite has been synthesized by a simple solid-state pyrolysis method from an in situ route. The results indicate that the synthesized sample has a large specific surface area (S BET) of 198 m2 g?1, and the WC nanoparticles (NPs) with a narrow particle size are well dispersed on the graphitic carbon. After loading Pt nanoparticles, the prepared Pt/WC/GC catalyst exhibits a mass activity of 416.1 mA mg?1 Pt toward methanol electrooxidation, which is much higher than that of commercial Pt/C (JM) (231.2 mA mg?1 Pt). Moreover, the onset potential is 100 mV more negative than that on Pt/C (JM) electrocatalyst. In addition, the Pt/WC/GC catalyst has stronger resistance to CO poisoning than the commercial Pt/C (JM). Its superior electrochemical performance could be attributed not only to the synergistic effect between Pt and WC NPs but also to the excellent electrical conductivity of GC and proper porous structure for desirable mass transportation in a porous electrode.  相似文献   

9.
《Electroanalysis》2004,16(17):1451-1458
A new carbon electrode material, obtained by mixing single wall carbon nanotubes (SWNTs) with a mineral oil binder is studied. Carbon nanotube pastes show the special properties of carbon nanotubes combined with the various advantages of composite electrodes such as a very low capacitance (background current) and the possibility of an easy preparation, modification and renewal. A better knowledge of the characteristics of electrode reactions at carbon nanotube paste (CNTP) electrodes was obtained studying the electron transfer rates of various redox couples under different pretreatment conditions. A critical comparison with carbon paste (CP), platinum (Pt) and glassy carbon (GC) electrodes was also carried out. Capacitance and resistance values were also calculated for all electrodes investigated. Both untreated and treated CNTP electrodes showed a low resistance while the capacitance was markedly reduced with CNTP electrodes previously treated with concentrated nitric acid. An electrochemical pretreatment on CNTP electrodes was developed which showed an excellent result towards two‐electron quinonic structure species. After this treatment the heterogeneous standard rate constants for p‐methylaminophenol sulfate (MAP) and dopamine resulted to be significantly higher (2.1×10?2 cm/s and 2.0×10?2 cm/s, respectively) than those obtained with the other electrodes studied. Reproducibility, stability and storage characteristics of CNTP electrodes were also reported.  相似文献   

10.
The electrochemical reduction of oxygen on binary Pt–Ru alloy deposited onto microporous–mesoporous carbon support was studied in 0.5 M H2SO4 solution using cyclic voltammetry, rotating disk electrode (RDE), and impedance method. The microporous–mesoporous carbon support C(Mo2C) with specific surface area of 1,990 m2?g?1 was prepared from Mo2C at 600 °C using the chlorination method. Analysis of X-ray diffraction, photoelectron spectroscopy, and high-resolution transmission electron microscopy data confirms that the Pt–Ru alloy has been formed and the atomic fraction of Ru in the alloy was ~0.5. High cathodic oxygen reduction current densities (?160 A?m?2 at 3,000 rev?min?1) have been measured by the RDE method. The O2 diffusion constant (1.9?±?0.3?×?10?5?cm2?s?1) and the number of electrons transferred per electroreduction of one O2 molecule (~4), calculated from the Levich and Koutecky–Levich plots, are in agreement with literature data. Similarly to the Ru/RuO2 system in H2SO4 aqueous solution, nearly capacitive behavior was observed from impedance data at very low ac frequencies, explained by slow electrical double-layer formation limited by the adsorption of reaction intermediates and products into microporous–mesoporous Pt–Ru–C(Mo2C) catalyst. All results obtained for C(Mo2C) and Pt–Ru–C(Mo2C) electrodes have been compared with corresponding data for commercial carbon VULCAN® XC72 (C(Vulcan)) and Pt–Ru–C(Vulcan) electrodes processed and measured in the same experimental conditions. Higher activity for C(Mo2C) and Pt–Ru–C(Mo2C) has been demonstrated.  相似文献   

11.
Titanium dioxide nanoparticle/gold nanoparticle/carbon nanotube (TiO2/Au/CNT) nanocomposites were synthesized, and then characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX). A TiO2/Au/CNT nanocomposite-modified glassy carbon (GC) electrode was prepared using the drop coating method and was investigated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and amperometric current–time response (I-T). The modified material is redox-active. The nonenzymatically detected amount of ascorbic acid (AA) on the TiO2/Au/CNT electrode showed a linear relationship with the AA concentration, for concentrations from 0.01 to 0.08 μM; the sensitivity was 117,776.36 μA?·?cm?2?·?(mM)?1, and the detection limit was 0.01 μM (S/N?=?3). The results indicated that the TiO2/Au/CNT nanocomposite-modified GC electrode exhibited high electrocatalytic activity toward AA. This paper describes materials consisting of a network of TiO2, Au, and MWCNTs, and the investigation of their synergistic effects in the detection of AA.  相似文献   

12.
以水热法并进一步焙烧合成脊椎状NiCo2O4纳米棒,通过透射电子显微镜(TEM)、X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)和热重分析仪(TG)等来表征其结构形态及热稳定性.采用线性扫描法(LSV)、循环伏安(CV)研究所制备催化剂的在玻碳和旋转圆盘电极上的电催化活性:在0.1 mol·L-1 KOH溶液中的电催化析氧反应(OER)和电催化氧还原反应(ORR).研究结果表明,所制备的脊椎状NiCo2O4纳米棒有大量的不饱和态,200℃焙烧制备的脊椎状NiCo2O4纳米棒析氧过电位最小可达309 mV,Tafel斜率145.6 mV/dec,其氧还原极限电流密度在1600 rmp可达到5.095 mA·cm-2,电子转移数在3.2~3.8之间,接近四电子转移机理,其优良电化学性能可能是由于暴露了更多的边缘缺陷的缘故.  相似文献   

13.
In this paper, porous carbon was synthesized by an activation method, with phenolic resin as carbon source and nanometer calcium carbonate as activating agent. Sulfur–porous carbon composite material was prepared by thermally treating a mixture of sublimed sulfur and porous carbon. Morphology and electrochemical performance of the carbon and sulfur–carbon composite cathode were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectra (EIS), and galvanostatic charge–discharge test. The composite containing 39 wt.% sulfur obtained an initial discharge capacity of about 1,130 mA?h g?1 under the current density of 80 mA?g?1 and presented a long electrochemical stability up to 100 cycles.  相似文献   

14.
Platinum–ruthenium (Pt–Ru) nanoparticles were successfully deposited, for the first time, on the surface of SnO2 nanowires grown directly on carbon paper (Pt–Ru/SnO2 NWs/carbon paper) by potentiostatic electrodeposition method. The resultant Pt–Ru/SnO2 NWs/carbon paper composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrocatalytic activities of these composite electrodes for methanol oxidation were investigated and higher mass and specific activities in methanol oxidation were exhibited as compared to Pt–Ru catalysts deposited on glassy carbon electrode.  相似文献   

15.
Fuel cell electrodes were prepared from Pt nanocluster activated hierarchical microporous-mesoporous carbon powders. The carbon supports were synthesized from molybdenum carbide applying the high-temperature chlorination method. Six different synthesis temperatures within the range from 600 to 1000 °C were used for preparation of carbon supports. Thermogravimetric analysis, X-ray diffraction, low-temperature nitrogen sorption, and high-resolution scanning electron microscopy methods were used to characterize the structure of the electrode materials and symmetrical membrane electrode assemblies (MEAs). The MEAs prepared were used to conduct the proton exchange membrane fuel cell (PEMFC)single-cell measurements. The polarization and power density curves for single cells were calculated to evaluate the activity of the catalyst materials synthesized. The electrochemically active surface area (from 2.4 to 11.9 m2 g?1) was obtained in order to estimate the contact surface areas of platinum and Nafion® electrolyte. The values of the electrolyte resistance, polarization resistance, and cell degradation rate were calculated from electrochemical impedance spectroscopy data. The carbon materials synthesized within temperature range from 600 to 850 °C were found to be the most suitable supports for PEMFCs, having higher maximum power density values and better stability (cell potential degradation 240 μV h?1) than commercial carbon-based (Vulcan XC72; 670 μV h?1) single cells.  相似文献   

16.
利用表面活性剂十二烷基磺酸钠(SDSN)的调控合成不同粒径的硒模板和铂纳米空球(Pthollow),并将其修饰于玻碳(GC)基底即可制得Pthollow/GC电极;采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、高分辨透射电子显微镜(HR-TEM)和X射线光电子能谱等观察表征了Pthollow样品的形貌与组成;以甲醇为探针分子,研究Pthollow/GC和电沉积铂电极(Ptnano/GC)对甲醇氧化的电催化活性. 结果表明,由铂原子簇团构筑的多孔铂纳米空球粒径均匀,分散性好;用4 μmol·L-1 SDSN控制合成的直径为130 nm的Pthollow制备的Pthollow/GC电极对甲醇氧化的电催化活性最佳.  相似文献   

17.
A sensitive and selective imprinted electrochemical sensor for the determination of aflatoxin B1 (AFB1) was constructed on a glassy carbon electrode by stepwise modification of functional multiwalled carbon nanotubes (MCNTs), Au/Pt bimetallic nanoparticles (Au/PtNPs), and a thin imprinted film. The fabrication of a homogeneous porous poly o-phenylenediamine (POPD)-grafted Au/Pt bimetallic multiwalled carbon nanotubes nanocomposite film was conducted by controllable electrodepositing technology. The sensitivity of the sensor was improved greatly because of the nanocomposite functional layer; the proposed sensor exhibited excellent selectivity toward AFB1 owing to the porous molecular imprinted polymer (MIP) film. The surface morphologies of the modified electrodes were characterized using a scanning electron microscope. The performance of the imprinted sensor was investigated by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy in detail. A linear relationship between the sensor response signal and the logarithm of AFB1 concentrations ranging from 1?×?10?10 to 1?×?10?5 mol L?1 was obtained with a detection limit of 0.03 nmol L?1. It was applied to detect AFB1 in hogwash oil successfully.  相似文献   

18.
Olivine-type LiFePO4 is one of the most promising cathode materials for lithium-ion batteries, but its poor conductivity and low lithium-ion diffusion limit its practical application. The electronic conductivity of LiFePO4 can be improved by carbon coating and metal doping. A small amount of La-ion was added via ball milling by a solid-state reaction method. The samples were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM)/mapping, differential scanning calorimetry (DSC), transmission electron microscopy (TEM)/energy dispersive X-ray spectroscopy (EDS), and total organic carbon (TOC). Their electrochemical properties were investigated by cyclic voltammetry, four-point probe conductivity measurements, and galvanostatic charge and discharge tests. The results indicate that these La-ion dopants do not affect the structure of the material but considerably improve its rate capacity performance and cyclic stability. Among the materials, the LiFe0.99La0.01PO4/C composite presents the best electrochemical behavior, with a discharge capacity of 156 mAh g?1 between 2.8 and 4.0 V at a 0.2 C-rate compared to 104 mAh g?1 for undoped LiFePO4. Its capacity retention is 80% after 497 cycles for LiFe0.99La0.01PO4/C samples. Such a significant improvement in electrochemical performance should be partly related to the enhanced electronic conductivities (from 5.88?×?10?6 to 2.82?×?10?3 S cm?1) and probably the mobility of Li+ ion in the doped samples. The LiFe0.99La0.01PO4/C composite developed here could be used as a cathode material for lithium-ion batteries.  相似文献   

19.
采用脉冲微波辅助化学还原法制备了钴-聚吡咯-碳(Co-PPy-C)载Pt 催化剂(Pt/Co-PPy-C),其中Pt 的总质量占20%. 利用透射电镜(TEM)、光电子射线能谱分析(XPS)和X射线衍射(XRD)研究了催化剂的结构,用循环伏安(CV)、线性扫描伏安(LSV)等方法考察了其电化学活性及氧还原反应(ORR)动力学特性及耐久性. Pt/Co-PPy-C电催化剂的金属颗粒直径约1.8 nm,略小于商用催化剂Pt/C(JM)颗粒尺寸(约2.5 nm);催化剂在载体上分散均匀,粒径分布范围较窄. Pt/Co-PPy-C的电化学活性比表面积(ECSA)(75.1 m2·g-1)高于商用催化剂的ECSA(51.3 m2·g-1). XPS测试表明,自制催化剂表面的Pt 主要以零价形式存在. 而XRD结果显示,自制催化剂中Pt(111)峰最强,Pt 主要为面心立方晶格. Pt/Co-PPy-C具有与Pt/C(JM)相同的半波电位;在0.9 V下,Pt/Co-PPy-C的比活性(1.21 mA·cm-2)高于商用催化剂的比活性(1.04 mA·cm-2),表现出更好的ORR催化活性.动力学性能测试表明催化剂的ORR反应以四电子路线进行. CV测试1000 圈后,Pt/Co-PPy-C和Pt/C(JM)的ECSA 分别衰减了13.0%和24.0%,可见自制催化剂的耐久性高于商用Pt/C(JM),在质子交换膜燃料电池(PEMFC)领域有一定的应用前景.  相似文献   

20.
Graphene nanosheets, polyaniline (PANI), and nanocrystallites of transition metal ferrite {Fe3O4 (Mag), NiFe2O4 (NiF), and CoFe2O4 (CoF)} have been prepared and characterized via XRD, FTIR, SEM, TEM, UV–vis spectroscopy, cyclic voltammetry, galvanostatic charge discharges, and impedance spectroscopy. Electrochemical measurements showed that supercapacitances of hybrid electrodes made of the ternary materials are higher than that of hybrid electrode made of binary or single material. The ternary hybrid CoF/graphene (G)/PANI electrode exhibits a highest specific capacitance reaching 1123 Fg?1, an energy density of 240 Wh kg?1 at 1 A g?1, and a power density of 2680 Wkg?1 at 1 A g?1 and outstanding cycling performance, with 98.2% capacitance retained over 2000 cycles. The extraordinary electrochemical performance of the ternary CoF/G/PANI hybrid can be attributed to the synergistic effects of the individual components. The PANI conducting polymer enhances an electron transport. The Ferrite nanoparticles prevent the restocking of the carbon sheets and provide Faradaic processes to increase the total capacitance.  相似文献   

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