共查询到20条相似文献,搜索用时 15 毫秒
1.
Ki Tae Park Un Ho JungDong Woong Choi Kook ChunHyang Mee Lee Sung Hyun Kim 《Journal of power sources》2008
Recast Nafion® composite membranes containing ZrO2–SiO2 binary oxides with different Zr/Si ratios are investigated for polymer electrolyte membrane fuel cells (PEMFCs) at temperatures above 100 °C. Fine particles of the ZrO2–SiO2 binary oxides, same as an inorganic filter, are synthesized from a sodium silicate and a carbonate complex of zirconium by a sol–gel technique. The composite membranes are prepared by blending a 10% (w/w) Nafion®-water dispersion with the inorganic compound. All composite membranes show higher water uptake than unmodified membranes, and the proton conductivity increases with increasing zirconia content at 80 °C. By contrast, the proton conductivity decreases with zirconia content for the composite membranes containing binary oxides at 120 °C. The composite membranes are tested in a 9-cm2 commercial single cell at both 80 °C and 120 °C in humidified H2/air under different relative humidity (RH) conditions. Composite membrane containing the ZrO2–SiO2 binary oxide (Zr/Si = 0.5) give the best performance of 610 mW cm−1 under conditions of 0.6 V, 120 °C, 50% RH and 2 atm. 相似文献
2.
《Journal of power sources》2001,94(2):212-218
We report on in situ and ex situ concentration measurements in lithium/polymer–electrolyte/lithium cells during cycling. We have used three different methods which give complementary results, in good agreement with theoretical predictions and previous concentration measurements by Raman confocal microspectroscopy. Our methods allow to obtain concentration maps in the electrolyte, in particular, when dendrites are observed: from these measurements, we can correlate the onset of dendritic growth with local concentration gradients. 相似文献
3.
《Journal of power sources》2004,129(2):303-311
Amorphous poly(ethylene oxide) (PEO)–SiO2 composites are prepared by in situ reactions that involve the simultaneous formation of the polymer network and inorganic nanoparticles. The polymer matrix is formed by ultraviolet irradiation of a PEO macromer, and silica is produced in situ by the sol–gel method. The PEO–SiO2 composite mixed with LiBF4 is used as a lithium-ion conducting solid electrolyte and electrochemical transport properties such as ionic conductivity and Li+ transference number are measured. A significant increase in the Li+ transference number, up to 0.56, is found together with a slight decrease in the ionic conductivity. The results are interpreted in terms of interactions between the surface OH groups of the inorganic particles, the cations, the anions, and the ether oxygen atoms on the PEO backbone. 相似文献
4.
Zhen Zheng Ning Li Chun-Qing Wang De-Yu Li Yong-Ming Zhu Gang Wu 《International Journal of Hydrogen Energy》2012
In this work, nickel-based electrodes were prepared using composite electrodeposition technique in a nickel sulphamate bath containing suspended micro- or nano-sized CeO2 particles. The prepared Ni–CeO2 composite electrodes exhibit an enhanced high catalytic activity toward hydrogen evolution reaction (HER) in alkaline solutions. X-ray diffraction patterns indicated that the CeO2 particles have been successfully incorporated into the Ni matrix and altered the texture coefficient (TC) of the Ni layer. The morphology of the obtained coatings was characterized by Scanning Electron Microscopy, and the CeO2 content was determined by coupled energy dispersive X-ray spectrometry. The thermal stability of the composite electrodes was analyzed by thermogravimetric and differential scanning calorimetry, showing a good thermal stability. The catalytic activity of the composite electrodes for HER was measured by steady-state polarization and electrochemical impedance spectroscopy techniques in 1.0 M NaOH solution at room temperature. The exchange current density of HER on the Ni–CeO2 composite electrodes was much higher than that on Ni electrode. EIS results suggested that a synergetic effect on HER may exist between CeO2 particles and Ni matrix. Compared to nano-CeO2, the micro-CeO2 derived composite electrodes showed higher electrochemical activity. The possible correlation among particle size, content and catalytic activity is discussed. 相似文献
5.
Atsushi Sakuda Hirokazu KitauraAkitoshi Hayashi Kiyoharu TadanagaMasahiro Tatsumisago 《Journal of power sources》2009
All-solid-state lithium secondary batteries using LiCoO2 active materials coated with Li2SiO3 and SiO2 oxide films and Li2S–P2S5 solid electrolytes were fabricated and their electrochemical performance was investigated. The electrochemical performace of the all-solid-state cells at a high voltage region was highly improved by using oxide-coated LiCoO2. The oxide coatings are effective in suppressing the formation of an interfacial resistance between LiCoO2 and the solid electrolyte at a high cutoff voltage of 4.6 V (vs. Li). As a result, charge–discharge capacities and cycle performance at the cutoff voltage were improved. The cell with Li2SiO3-coated LiCoO2 showed a large initial discharge capacity of 130 mAh g−1 and a good capacity retention of 110 mAh g−1 after 50th cycles at the cutoff voltage of 4.6 V (vs. Li). 相似文献
6.
《Journal of power sources》2004,134(2):211-221
Polyvinyl chloride (PVC)-based composite polymer electrolyte films consisting of PVC–LiCF3SO3–SiO2 are prepared by the solution-casting method. The electrical properties of the electrolyte are investigated for ionic conductivity and its dependence on temperature. The electrolyte with the highest ionic conductivity is used to fabricate a LiCoO2/PVC–LiCF3SO3–SiO2/mesocarbon microbeads (MCMB) battery. The charge–discharge characteristics and performance of the battery at room temperature are evaluated to ascertain the effective viability, of these solid electrolytes in lithium-polymer batteries. Battery performances is also investigated at 313, 323 and 333 K. 相似文献
7.
8.
H.S. Thiam W.R.W. Daud S.K. Kamarudin A.B. Mohamad A.A.H. Kadhum K.S. Loh E.H. Majlan 《International Journal of Hydrogen Energy》2013
One of the major challenges for direct methanol fuel cells is the problem of methanol crossover. With the aim of solving this problem without adverse effects on the membrane conductivity, Nafion/Palladium–silica nanofiber (N/Pd–SiO2) composite membranes with various fiber loadings were prepared by a solution casting method. The silica-supported palladium nanofibers had diameters ranging from 100 nm to 200 nm and were synthesized by a facile electro-spinning method. The thermal properties, ionic exchange capacities, water uptake, proton conductivities, methanol permeabilities, chemical structures, and micro-structural morphologies were determined for the prepared membranes. It was found that the transport properties of the membranes were affected by the fiber loading. All of the composite membranes showed higher water uptake and ion exchange capacities compared to commercial Nafion 117 and proved to be thermally stable for use as proton exchange membranes. The composite membranes with optimum fiber content (3 wt%) showed an improved proton conductivity of 0.1292 S cm−1 and a reduced methanol permeability of 8.36 × 10−7 cm2 s−1. In single cell tests, it was observed that, the maximum power density measured with composite membrane is higher than those of commercial Nafion 117. 相似文献
9.
Pr2NiO4–Ag composite was synthesized and evaluated as cathode component for low temperature solid oxide fuel cells based on ceria-carbonate composite electrolyte. X-ray diffraction analysis reveals that the formation of a single phase K2NiF4–type structure occurs at 1000 °C and Pr2NiO4–Ag composite shows chemically compatible with the composite electrolyte. Symmetrical cells impedance measurements prove that Ag displays acceptable electrocatalytic activity toward oxygen reduction reaction at the temperature range of 500–600 °C. Single cells with Ag active component electrodes present better electrochemical performances than those of Ag-free cells. An improved maximum power density of 695 mW cm−2 was achieved at 600 °C using Pr2NiO4–Ag composite cathode, with humidified hydrogen as fuel and air as the oxidant. Preliminary results suggest that Pr2NiO4–Ag composite could be adopted as an alternative cathode for low temperature solid oxide fuel cells. 相似文献
10.
Active and stable Ni–Fe–SiO2 catalysts prepared by sol–gel method were employed for direct decomposition of undiluted methane to produce hydrogen and carbon filaments at 823 K and 923 K. The results indicated that the lifetime of Ni–Fe–SiO2 catalysts was much longer than Ni–SiO2 catalyst at a higher reaction temperature such as 923 K, however, a reverse trend was shown when methane decomposition took place at a lower reaction temperature such as 823 K. XRD studies suggested that iron atoms had entered into the Ni lattice and Ni–Fe alloy was formed in Ni–Fe–SiO2 catalysts. The structure of the carbon filaments generated over Ni–SiO2 and Ni–Fe–SiO2 was quite different. TEM studies showed that “multi-walled” carbon filaments were formed over 75%Ni–25%SiO2 catalyst, while “bamboo-shaped” carbon filaments generated over 35%Ni–40%Fe–25%SiO2 catalysts at 923 K. Raman spectra of the generated carbons demonstrated that the graphitic order of the “multi-walled” carbon filaments was lower than that of the “bamboo-shaped” carbon filaments. 相似文献
11.
12.
Razack Imran Jafri N. Sujatha N. Rajalakshmi S. Ramaprabhu 《International Journal of Hydrogen Energy》2009
Bi-functional catalysts based on Au supported on oxide based nanomaterials for use in fuel cells were evaluated by electrochemical methods for oxygen reduction reaction (ORR) in Polymer Electrolyte Membrane Fuel Cell (PEMFC). Metal oxide coated multi walled carbon nanotubes (MWNTs) (MnO2/MWNT and ZnO/MWNT) were prepared by reduction of potassium permanganate and oxidation of Zn powder on MWNT surface respectively. Au–MnO2/MWNT and Au–ZnO/MWNT were prepared by chemical reduction of chloroauric acid on MnO2/MWNT and ZnO/MWNT. The samples were characterized and linear sweep voltammetric studies were performed in N2 saturated, O2 saturated and methanol containing 1 M KOH solution and the results have been discussed. A single fuel cell was also constructed using Au–MnO2/MWNT and Au–ZnO/MWNT as ORR electrocatalysts. A maximum power density of 45 mW/cm2 and 56 mW/cm2 was obtained with Au–MnO2/MWNT and Au–ZnO/MWNT respectively. Additionally, the methanol tolerance of these electrocatalysts has been investigated and results have been discussed. 相似文献
13.
14.
Three-dimensional Li2O–NiO–CoO composite thin-film electrodes deposited on stainless steel substrates were synthesized by the electrostatic spray deposition (ESD) technique at 240 and 295 °C. The morphology of the composite was investigated by scanning electron microscopy. X-ray diffraction indicated that the as-deposited films are composites of Li2O, NiO and CoO. The effects of the solvent used to dissolve the starting materials on the morphology and electrochemical performance of the thin-film electrodes were also investigated. It was found that the as-deposited thin-film electrodes exhibited a high reversible capacity (>800 mAh g−1 when cycled between 0.01 and 3 V at a cycling rate of 0.5 C), good capacity retention, and outstanding rate capability. The superior electrochemical performance may have resulted from the combination of the very porous structure and the three-dimensional network of the as-deposited thin-film electrodes, which contributed to a high surface area, favoured lithium-ion diffusion, and formed a stable integral structure. The thin-film electrodes could be promising anodes for use in high power and high energy density lithium-ion batteries. 相似文献
15.
A type of Yb2O3 doped Ni–ZrO2 catalyst for ethanol steam reforming was developed, and displayed excellent catalyzing performance for the selective formation of H2 and CO2. Over a Ni1.25Zr1Yb0.8 catalyst, STY(H2) can maintain stable at the level of 0.396 mol h−1 g−1 (data taken 120 h after the reaction started) under the reaction conditions of 0.5 MPa and 723 K, which was 1.6 times that (0.247 mol h−1 g−1) of the Yb-free counterpart Ni1.25Zr1. Characterization of the catalyst revealed that dissolution of an appropriate amount of Yb3+ ions in the zirconia host resulted in the formation of the Zr–Yb composite oxide with cubic-ZrO2 structure, c-(Zr–Yb)Oz, which inhibited effectively the transformation of c-ZrO2 to thermodynamically more stable m-ZrO2, thus avoiding sintering of the (Zr–Yb)Oz composite. It was demonstrated that the doping of Yb2O3 to Ni–ZrO2 changed also the valence states or the micro-environments of the Ni-species at the quasi-active surface of the tested catalyst, which was conducive to inhibiting agglomeration of the Nix0–Nin+ species active catalytically, with resulting in maintaining the high metallic nickel dispersion and inhibiting coking. The aforementioned two factors both contributed to improving the activity and operating stability as well as heat-resistant quality of the catalyst. 相似文献
16.
17.
A prior paper has presented a novel design of a heavy duty truck engine fuelled with H2. In this design, the customary in-cylinder Diesel injector and glow plug are replaced with a main chamber fuel injector and a jet ignition pre-chamber. The jet ignition pre-chamber is a small volume that is connected to the in-cylinder through calibrated orifices accommodating another fuel injector and a glow or a spark plug that controls the start of combustion. This design permits to operate the engine in four different modes: traditional compression ignition (CI), diffusion, Diesel-like (M1); mixed gasoline/Diesel-like (M2); traditional spark ignition (SI), premixed, gasoline-like (M3); premixed, homogeneous charge compression ignition HCCI-like (M4). In the mode diffusion with jet ignition (M1), an injection occurs in the jet ignition pre-chamber before the main chamber fuel is injected and the engine operates therefore mostly Diesel-like. In the mode mixed diffusion/premixed Diesel/gasoline-like (M2) an injection occurs in the jet ignition pre-chamber after only part of the main chamber fuel is injected and mixed with air. In the mode premixed with jet ignition (M3), an injection occurs in the jet ignition pre-chamber after the main chamber fuel is injected and mixed with air and the engine operates gasoline-like. Finally, in the mode premixed without jet ignition (M4), no injection occurs in the jet ignition pre-chamber and the engine operates HCCI-like. Modelling results have already been presented and discussed with H2 as the main chamber and pre-chamber fuel. This paper considers the option to accommodate a second main chamber injector that will inject the NH3 that will then burn in air thanks to the hot combusting gases from the combustion of H2 and air using the modes M1 and M2 described above. The mode M3 also of interest is not considered here. First results of simulations show the opportunity to achieve better than Diesel fuel energy conversion efficiency thanks to the reduced heat losses of the “cold burning” NH3 and suggest to perform the experiments needed to further support the findings. 相似文献
18.
Hua-Ping Ren Qing-Qing Hao Wei Wang Yong-Hong Song Jie Cheng Zhong-Wen Liu Zhao-Tie Liu Jian Lu Zhengping Hao 《International Journal of Hydrogen Energy》2014
The SiO2 and Ni–SiO2 were synthesized via the complex-decomposition method by using different organic acids as the complexing agent and fuel. The Ni-supported SiO2 from different sources was prepared by the incipient impregnation method. The Ni–SiO2 and Ni/SiO2 were comparatively evaluated for carbon dioxide reforming of methane (CDR) under severe conditions of CH4/CO2 = 1.0, T = 750 °C, GHSV = 53200 mL g−1 h−1, and P = 0.1–1.0 MPa. The materials were fully characterized by XRD, XPS, TEM, TG-DSC, H2-TPR, and N2 adsorption-desorption at −196 °C. It was found that the complexing agent and preparation method of the catalyst significantly affected its surface area, the size and dispersion of Ni, the reduction behavior, and the coking and sintering properties, which determine the activity and stability of the catalyst for CDR. As a result, a highly active and stable Ni–SiO2 for pressurized CDR was obtained by optimizing the complexing agent. 相似文献
19.
Yttria-stabilized bismuth oxides (YSB) are cooperated to (La,Sr)MnO3 (LSM) to form composite cathodes for intermediate-temperature solid oxide fuel cells. The composite electrodes are fabricated with screen-printing technique and characterized using electrochemical impedance spectroscopy. The interfacial polarization resistances (Rp) of the LSM–YSB electrodes on yttria-stabilized zirconia (YSZ), samaria-doped ceria (SDC), and YSB electrolytes are analyzed regarding the electrode composition and operating temperature. Rp decreases with the increase of YSB content up to 80 wt.% in the LSM–YSB composite. When YSZ is used as the electrolyte, the lowest Rp is 0.14 Ω cm2 at 700 °C, which is only 1.8% of that for a pure LSM electrode, 5.6% of that reported for LSM–YSZ composites, and 13.2% of that for reported LSM–GDC (gadolinia-doped ceria) electrodes, demonstrating that YSB is very effective to enhance the performance of LSM-based cathodes. The electrode performance is also affected by the electrolyte substrate. LSM electrodes without any YSB exhibit obviously different performance on YSZ, SDC and YSB electrolytes. However, when YSB is cooperated, Rp on different electrolytes tends to become equivalent, especially for electrodes with high YSB content. Further analysis shows that their electrochemical performance is contributed dominantly from the electrode bulk whereas the contribution from the electrode/electrolyte interface is negligible, suggesting weak electrolyte effect on the performance of LSM–YSB composite electrodes. 相似文献
20.
Rapee Gosalawit-Utke Chiara Milanese Payam Javadian Julian Jepsen Daniel Laipple Fahim Karmi Julián Puszkiel Torben R. Jensen Amedeo Marini Thomas Klassen Martin Dornheim 《International Journal of Hydrogen Energy》2013
Nanoconfinement of 2LiBH4–MgH2–TiCl3 in resorcinol–formaldehyde carbon aerogel scaffold (RF–CAS) for reversible hydrogen storage applications is proposed. RF–CAS is encapsulated with approximately 1.6 wt. % TiCl3 by solution impregnation technique, and it is further nanoconfined with bulk 2LiBH4–MgH2 via melt infiltration. Faster dehydrogenation kinetics is obtained after TiCl3 impregnation, for example, nanoconfined 2LiBH4–MgH2–TiCl3 requires ∼1 and 4.5 h, respectively, to release 95% of the total hydrogen content during the 1st and 2nd cycles, while nanoconfined 2LiBH4–MgH2 (∼2.5 and 7 h, respectively) and bulk material (∼23 and 22 h, respectively) take considerably longer. Moreover, 95–98.6% of the theoretical H2 storage capacity (3.6–3.75 wt. % H2) is reproduced after four hydrogen release and uptake cycles of the nanoconfined 2LiBH4–MgH2–TiCl3. The reversibility of this hydrogen storage material is confirmed by the formation of LiBH4 and MgH2 after rehydrogenation using FTIR and SR-PXD techniques, respectively. 相似文献