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In this work some electrochemical characteristics of all solid double layer capacitors prepared by high surface carbon and Nafion polymer electrolyte are reported. Carbon composite electrodes with a Nafion loading of 30 wt.% were prepared and evaluated. Nafion 115 membrane, recast Nafion membrane and 1 M H2SO4 solution in a matrix of glass fiber have been used as electrolyte, in the double layer capacitors. The different double layer capacitors (DLCs) have been evaluated by electrochemical impedance spectroscopy. The capacitor with a recast Nafion electrolyte exhibits a proton conductivity of about 3x10-2 S cm-1 at ambient temperature, that is higher of that reported for solid electrolytes (10-3 to 10-4 S cm-1) in the current literature on capacitors. A maximum of specific capacitance of 13 F/g of active materials ( ) corresponding to 52 F/g for a single electrode measured in a three-electrode arrangement has been achieved with the capacitor with recast Nafion. The capacitance of the capacitor with recast Nafion electrolyte, evaluated in low-frequency region below 10 mHz, was practically equivalent at that with sulphuric acid electrolyte. The interpretation of the characteristics of the microporous structure of carbon material of the electrodes by impedance analysis is also discussed.

Abstract Electrolyte-free fuel cell (EFFC) which holds the similar function with the traditional solid oxide fuel cell (SOFC) but possesses a completely different structure, has draw much attention during these years. Herein, we report a complex of MZSDC–LNCS (Mg 0.4 Zn 0.6 O/Ce 0.8 Sm 0.2 O 2− δ –Li 0.3 Ni 0.6 Cu 0.07 Sr 0.03 O 2− δ ) for EFFC that demonstrates a high electrochemical power output of about 600 mW cm −2 at 630 °C. The co-doped MZSDC is synthesized by a co-precipitation method. Semiconductor material of LNCS is synthesized by direct solid state reaction. The microstructure and morphology of the composite materials are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive X-ray spectrometer (EDS). The performance of the cell with a large size (6 × 6 cm 2 ) is comparable or even better than that of the conventional solid oxide fuel cells with large sizes. The maximum power output of 9.28 W is obtained from the large-size cell at 600 °C. This paper develops a new functional nanocomposite for EFFC which is conducive to its commercial use.

An ultracapacitor (UCap) based on carbon xerogel electrodes and sodium sulfate electrolyte was investigated in the voltage range between 0 and 1.8 V. Notwithstanding the high value of maximum voltage (1.8 V) the UCap exhibited excellent stability during 20000 of cycling test. Moreover, the achievement of this high voltage made possible to obtain high value of specific energy. The stability was possible because the potential limits of electrode-electrolyte decomposition at positive and negative electrodes were never achieved. This is because an asymmetric UCap with different amounts of carbon xerogel in the electrodes was used. The UCap with the carbon xerogel of BET specific surface area of 3100 m(2) g(-1) demonstrated a specific energy of 17.5 Wh kg(-1) and a specific capacitance of 156 F g(-1) and, retained 91% of initial capacitance after 20000 cycles of duration test. (C) 2012 Elsevier B.V. All rights reserved.

In the last ten years, the research of solid oxide fuel cells (SOFCs) or ceramic fuel cells (CFC) had focused on reducing the working temperature through the development of novel materials, especially the high ionic conductive electrolyte materials. Many progresses on single-phase electrolyte materials with the enhanced ionic conductivity have been made, but they are still far from the criteria of commercialization. The studies of ceria oxide based composite electrolytes give an alternative solution to these problems because of their impressive ionic conductivities and tunable ionic conduction behaviors. Significant advances in the understanding the ceria based composite material and construction of efficient fuel cell systems have been achieved within a short period. This report reviews recent developments of ceria-based composite from different aspects: materials, fundamentals, technologies, fabrication/construction parameters, electrochemistry and theoretical studies. Particular attention is given to ceria-carbonate (nano)composite, including its fuel cell performance, multi-ionic transport properties, advanced applications, corresponding electrode material and stability concerning. Besides, several novel fuel cell (FC) concepts like nanowire FC, all-nanocomposite FC and single-component/electrolyte-free fuel cell (SC-EFFC) are presented. This mini-review emphasizes the promise of ceria-based composites for advanced FC application and highlights the breakthrough of SC-EFFC research for high efficient energy conversion.

A new series of transparent gel polymer electrolytes are prepared by adding various weight percent of thiourea coupled with poly(ethylene oxide) for the application of dye-sensitized solar cells. Coupling of thiourea in the presence of iodine undergoes dimerization reaction to produce formamidine disulfide. Fourier Transform Infrared spectroscopy shows that the interactions of thiourea and formamidine disulfide with electronegative ether linkage of poly(ethylene oxide) results in conformational changes of gel polymer electrolytes. Electrochemical impedance spectroscopy and linear sweep voltammetry experiments reveal an increment in ionic conductivity and tri-iodide diffusion coefficient, for thiourea modified gel polymer electrolytes. Finally, the prepared electrolytes are used as a redox mediator in dye-sensitized solar cells and the photovoltaic properties were studied. Apart from transparency, the gel polymer electrolytes with thiorurea show higher photovoltaic properties compared to bare gel polymer electrolyte and a maximum photocurrent efficiency of 7.17% is achieved for gel polymer electrolyte containing 1 wt% of thiourea with a short circuit current of 11.79 mA cm-2 and open circuit voltage of 834 mV. Finally, under rear illumination, almost 90% efficiency is retained upon compared to front illumination.

This paper describes the testing of the gas-diffusion electrodes for polymer electrolyte membrane fuel cells utilizing phosphoric acid doped polybenzimidazole (PBI) electrolyte, which allows for an operating temperature as high as 200 °C. In order to determine the optimum structure of our anodes and cathodes, the platinum content in the Pt/C catalyst and catalyst loading were varied, as well as the loading of the PBI electrolyte dispersed in the catalyst layer. The different MEAs were tested in terms of their performance by recording polarization curves using pure oxygen and hydrogen. It was found that a high platinum content and a thin catalyst layer on both anode and cathode, gave the overall best performance. This was attributed to the different catalyst surface areas, the location of the catalyst in relation to the electrolyte membrane and particularly the amount of PBI dispersed in the catalyst layer. Scanning electron microscopy (SEM) was used in order to examine the cross-section of the MEAs and measure the thickness of the catalyst layers. With this information, it was possible to give an estimate of the porosity of the catalyst layer.

A previously published computational multi-phase model of a polymer-electrolyte membrane fuel cell cathode has been extended in order to account for the anode side and the electrolyte membrane. The model has been applied to study the water balance of a fuel cell during operation under various humidification conditions. It was found that the specific surface area of the electrolyte in the catalyst layers close to the membrane is of critical importance for the overall water balance. Applying a high specific electrolyte surface area close to the membrane (a water-uptake layer) can prevent drying out of the anode and flooding at the cathode while the average membrane water content is only weakly affected. The results also indicate that in contrast to common presumption membrane dehydration may occur at either anode or cathode side, entirely depending on the direction of the net water transport because the predominant transport mechanism is diffusion. Consequently, operating conditions with a high net water transport from anode to cathode should be avoided as it is important to keep the cathode catalyst layer well humidified in order to prevent high protonic losses. Addition of the micro-porous layer did not affect the overall water balance or membrane water content in our study.