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1.
Hydrogenation of benzene, toluene, o,m and p-xylene over Pt, Pd and Pt–Pd/Al2O3 catalysts has been studied. Experimental data show that when Pd is added to Pt catalysts, a decrease in activity and changes in selectivity occur. This is explained by the formation of electron-deficient and electrorich metallic species.
, , -, - - Pt, Pd Pt–Pd/Al2O3. , Pd Pt . .
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2.
Effect of methanol on the reduction kinetics of oxygen on highly dispersed catalysts 60Pt/C (HiSPEC 9100), 40Pt/carbon nanotubes, and CoFe/carbon nanotubes for the cathode of a direct methanol-oxygen fuel cell was studied. It was shown that the CoFe/carbon nanotubes catalyst surpasses the platinum systems in tolerance to the alcohol. It was found that the tolerance of the cathode catalyst strongly affects the current–voltage characteristics of the fuel cell, which is the principal result of the study and constitutes its scientific novelty. The maximum power density of an alkaline methanol-oxygen fuel cell with nonplatinum cathode (260 mW cm–2) exceeds the characteristics of similar fuel cells with platinum cathode catalysts, both obtained in the present study and described in the literature, which points to the practical importance of the study.  相似文献   

3.
Carbon-supported Ir3Sn/C and Ir/C catalysts were simply prepared with NaBH4 as a reducing agent under the protection of ethylene glycol at room temperature. TEM and X-ray diffraction (XRD) data showed that the catalysts with small particle size exhibited the typical characteristic of a crystalline Ir fcc structure. Their electro-catalytic activities in comparison with Pt/C and Pt3Sn/C catalysts also prepared by the NaBH4 reduction process were characterized by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and chronoamperometry (CA) techniques. The results indicated that Ir-based catalysts showed superior electro-catalytic activity towards ethanol oxidation to Pt/C and Pt3Sn/C catalysts, mainly at low potential region. During single-cell tests at 90 °C, better performances of Ir-based catalysts as anodes were obtained compared to that of Pt/C catalyst. The comparable overall performance of Ir3Sn/C to Pt3Sn/C makes it a promising alternative choice of anode catalyst for direct ethanol fuel cells.  相似文献   

4.
A microfluidic fuel cell architecture incorporating flow-through porous electrodes is demonstrated. The design is based on cross-flow of aqueous vanadium redox species through the electrodes into an orthogonally arranged co-laminar exit channel, where the waste solutions provide ionic charge transfer in a membraneless configuration. This flow-through architecture enables improved utilization of the three-dimensional active area inside the porous electrodes and provides enhanced rates of convective/diffusive transport without increasing the parasitic loss required to drive the flow. Prototype fuel cells are fabricated by rapid prototyping with total material cost estimated at 2 USD/unit. Improved performance as compared to previous microfluidic fuel cells is demonstrated, including power densities at room temperature up to 131 mW cm-2. In addition, high overall energy conversion efficiency is obtained through a combination of relatively high levels of fuel utilization and cell voltage. When operated at 1 microL min-1 flow rate, the fuel cell produced 20 mW cm-2 at 0.8 V combined with an active fuel utilization of 94%. Finally, we demonstrate in situ fuel and oxidant regeneration by running the flow-through architecture fuel cell in reverse.  相似文献   

5.
Gas diffusion electrodes for high temperature polymer electrolyte fuel cells (PEFCs) have been prepared by using a novel proton conductive sulfonated polyimide (SPI) electrolyte. The catalyst layer was composed of Pt-loaded carbon black (Pt-CB) and SPI ionomer. The polarization properties and the microstructure of the catalyst layer were investigated as a function of the SPI/CB weight ratio. The anodic polarization was found to be negligibly small for all the compositions examined. The highest cathode performance was obtained at SPI/CB = 0.5 (by weight), where the best balance of high catalyst utilization and oxygen gas diffusion rate through the ionomer was obtained.  相似文献   

6.
In the search for noble-metal-free cathode materials resistant to acid electrolytes and capable of catalysing the conversion of oxygen, thermogravimetric methods have been used to determine the conditions of preparation, to analyse the chemical properties, and to characterise the pore structure of the potential catalysts. The paper comprises results of investigations on inorganic compounds, such as ammonium tungstates, chromates, vanadates, molybdate and permanganate, and on organic polymers, such as polyamide nitriles, other CN polymers and polyacenoquinone pyrolysates.  相似文献   

7.
During the last few decades organometallic methodologies have generated a number of highly effective electrocatalyst systems based on mono‐ and bimetallic nanosparticles having controlled size, composition and structure. In this microreview we summarize our results in fuel cell catalyst preparation applying triorganohydroborate chemistry, ‘reductive particle stabilization’ using organoaluminum compounds, and the controlled decomposition of organometallic complexes. The advantages of organometallic catalyst preparation pathways are exemplified with Ru? Pt nanoparticles@C as promising anode catalysts to be used in direct methanol oxidation fuel cells (DMFC) or in polymer electrolyte fuel cells (PEMFC) running with CO‐contaminated H2 as the feed. Recent findings with highly efficient PtCo3@C fuel cell catalysts applied for the oxygen reduction reaction (ORR) and with the effect of Se‐doping on Ru@C ORR catalysts clearly demonstrate the benefits of organometallic catalyst synthesis. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

8.
Direct methanol fuel cells(DMFCs) are very promising power source for stationary and portable miniature electric appliances due to its high efficiency and low emissions of pollutants. As the key material, catalysts for both cathode and anode face several problems which hinder the commercialization of DMFCs.In this review, we mainly focus on anode catalysts of DMFCs. The process and mechanism of methanol electrooxidation on Pt and Pt-based catalysts in acidic medium have been introduced. The influences of size effect and morphology on electrocatalytic activity are discussed though whether there is a size effect in MOR catalyst is under debate. Besides, the non Pt catalysts are also listed to emphasize though Pt is still deemed as the indispensable element in anode catalyst of DMFCs in acidic medium. Different catalyst systems are compared to illustrate the level of research at present. Some debates need to be verified with experimental evidences.  相似文献   

9.
The work contains the results of studies of a promising composite material of Sr2Fe1.5Mo0.5O6 + Ce0.8Sm0.2O1.9 for electrodes of symmetrical solid oxide fuel cells. It is shown that conductivity of the composite at 800°C is about 10 and 15 S/cm, for air and humid hydrogen, respectively, and polarization resistance of the electrodes in contact with the electrolyte based on doped lanthanum gallate under the same conditions is about 0.26 and 0.12 Ohm cm2. Tests of a symmetrical fuel cell with a planar design and the supporting gallate electrolyte with the thickness of 300 μm show that the cell can develop the power of about 0.5 W/cm2 at 800°C when air is supplied to the cathode and humid hydrogen is supplied to the anode. Analysis of polarization losses shows that the polarization of the oxygen electrode considerably exceeds the polarization of the anode.  相似文献   

10.
A novel design of plate-type microchannel reactor has been developed for fuel cell-grade hydrogen production.Commercial Cu/Zn/Al2O3 was used as catalyst for the reforming reaction,and its effectiveness was evaluated on the mole fraction of products,methanol conversion,hydrogen yield and the amount of carbon monoxide under various operating conditions.Subsequently,0.5 wt% Ru/Al2O3 as methanation catalyst was prepared by impregnation method and coupled with MSR step to evaluate the capability of methanol processor for CO reduction.Based on the experimental results,the optimum conditions were obtained as feed flow rate of 5mL/h and temperature of 250℃,leading to a low CO selectivity and high H2 yield.The designed reformer with catalyst coated layer was compared with the conventional packed bed reformer at the same operating conditions.The constructed fuel processor had a good performance and excellent capability for on-board hydrogen production.  相似文献   

11.
Electrospun materials have been gaining great interest in the energy sector. Their tunability and robustness make them highly attractive, particularly for proton-exchange membrane fuel cell (PEMFC) electrodes. Conventional PEMFC electrodes, prepared by either spraying, painting, or slot-die coating, have not yet met the needs of large-scale PEMFC use. Electrospinning of fibrous materials has already shown great promise as an alternative methodology for electrode fabrication. Electrospinning has been used in fuel cell electrodes through two primary means: (1) segmented carbon or inorganic fibers to serve as precious metal catalyst support, and (2) high aspect ratio polymer/particle fibers to serve directly as the electrode. The use of electrospun fibrous electrodes has led to improved PEMFC durability and increased power output at low catalyst loadings, both of which are of paramount importance to large-scale commercialization of PEMFC electric vehicles.  相似文献   

12.
Two kinds of metal hydride alloys as the bi-functional catalyst concept for hydrogen generation and oxidation in hydrogen-diffusion electrodes were investigated. The AB5-type hydride electrode shows much higher catalytic activities than the Zr-based AB2-type hydride electrode. However, the activity of Zr-based hydride electrodes can be improved only after removal of zirconium oxides on surface by a 1.0 M HF solution. The experiments demonstrated that the both metal-hydride hydrogen-diffusion electrodes for cycles of hydrogen generation (12 h) and oxidation (12 h) had good stability under the current densities of 100 and 50 mA/cm2, respectively. The results also showed that small amounts of oxygen below 500 ppm and moisture up to 145,000 ppm in the hydrogen gas have little effect on the activity. It indicated that the hydride alloys as the non-noble-metal bi-functional catalysts in a reversible MH-air fuel cell have potential applications.  相似文献   

13.
A direct ethanol fuel cell offers an attractive, fairly high density, energy source, if an electrochemical system can be developed that efficiently carries out the 12-electron oxidation of ethanol to carbon dioxide and water. To that end, new catalyst systems must be developed along with fuel cell operating conditions that encourage the complete oxidation of ethanol, as opposed to the presently available platinum on carbon systems that tend to produce acetaldehyde (two-electron oxidation) or acetic acid (four-electron oxidation) products. It is found that a composite nanoparticulate catalyst containing platinum and tin oxide or platinum indium tin oxide allows the partial conversion of ethanol to its 12-electron oxidation products. Catalysts of this type can be formed using a modified polyol process. Elevation of the operating temperature of a proton exchange membrane fuel cell using the indicated catalysts to 130 degrees C facilitates the production of carbon dioxide and provides an improved current-voltage response.  相似文献   

14.
We report a high performance supported Pt catalyst, in which a perfluorosulfonic acid (Nafion) functionalized carbon black is used as support. The catalyst is characterized by infrared spectroscopy (IR), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The TEM image shows that the active Pt component is in nanoparticles and highly dispersed on the carbon black with an average particle size of 1.9 nm. The catalyst shows improved activity towards the methanol anodic oxidation and oxygen reduction reaction (ORR), resulting from the high dispersion of active Pt component. It leads to increases in electrochemically accessible surface areas and ion channels, as well as easier chargetransfer at polymer/electrolyte interfaces. The high platinum utilization and high performance of Pt/Nafion-C catalyst make it a promising electrocatalyst for fuel cell application.  相似文献   

15.
Microfluidic hydrogen fuel cell with a liquid electrolyte   总被引:1,自引:0,他引:1  
We report the design and characterization of a microfluidic hydrogen fuel cell with a flowing sulfuric acid solution instead of a Nafion membrane as the electrolyte. We studied the effect of cell resistance, hydrogen and oxygen flow rates, and electrolyte flow rate on fuel cell performance to obtain a maximum power density of 191 mW/cm2. This flowing electrolyte design avoids water management issues, including cathode flooding and anode dry out. Placing a reference electrode in the outlet stream allows for independent analysis of the polarization losses on the anode and the cathode, thereby creating an elegant catalyst characterization and optimization tool.  相似文献   

16.
17.
Small controlled amounts of palladium were electrochemically deposited onto various carbon supports from solutions of glycinate-chloride complexes of palladium(II) in order to obtain palladium catalysts suitable for use in fuel cells. The catalytic activity of the resulting catalytic layers was studied in reactions of reduction of atmospheric oxygen and oxidation of methanol and ethanol in acid and alkaline media by measuring cyclic voltammetric curves on a rotating disk electrode.  相似文献   

18.
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20.
Ni-La催化剂上乙醇水蒸气重整制氢——燃料电池氢源技术   总被引:2,自引:3,他引:2  
采用浸渍法制备出γ-Al2O3、SiO2和γ-Al2O3·SiO2负载的Ni-La催化剂,用XRD、TPR、XPS、H2-TPD、NH3-TPD和TG等手段对催化剂进行了表征,结果表明:这3种负载型催化剂中的活性组分Ni的分散度较高,La3 氧化物高度分散于载体表面.在温度为400℃、水醇比为4.0和液体空速为8.0 mL h-1 g-1cat的条件下,催化剂进行稳定性测试,结果表明:γ-Al2O3·SiO2负载的Ni-La催化剂在整个100 h稳定性测试过程中,氢气的选择性保持在67.0%左右,且稳定性良好.对经过稳定性测试后的Ni-La催化剂进行热重分析,发现γ-Al2O3·SiO2负载的Ni-La催化剂具有较少的积碳量,仅仅是0.86 g C·g-1cat,其中石墨碳占42.81%.  相似文献   

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