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In this study, we investigated the possibilities and combination of cost-effective materials of carbon (C) and lead (Pb) with polypropylene (PP) polymer as a new kind of bipolar plate for unitized regenerative fuel cell and polymer electrolyte membrane fuel cell systems. The homogeneous composite structure of C:Pb developed through facile mechanical milling process, and optimized. The new bipolar plate was fabricated with PP using compression molding process with hot pressing techniques. A dense and smooth surface morphology of C:Pb bipolar plate was acquired with the uniform thickness of 1.33 (±0.17) mm. Compared to C, an improved electrical properties (~20%) obtained to the powdered C:Pb composite materials because of homogeneous composition of Pb metal particles with large surface area of C. The C:Pb bipolar plate revealed an efficient water contact angle behavior than the C bipolar plate, where the water contact angle for C and C:Pb bipolar plates are 82.4° and 93.1°, respectively. A sophisticated electrochemical stability performance has obtained to the C:Pb bipolar plate in acidic condition. According to Tafel plots analysis, higher corrosion resistance has observed to the C:Pb bipolar plate than the C bipolar plate. The fabricated new kind of C:Pb bipolar plate provides the many advantageous, thus it proves the insights for further developments and applicability in the practical application. In the perspective view, the performances of C:Pb bipolar plate can be further altered through modification of different carbon structures together with impregnation of Pb nanostructured materials into the pores and/or embedded throughout the surface, and efficient conductive polymers.

Regular hydrophobized carbon paper cannot be used for unitized regenerative fuel cell applications as it corrodes at high potentials on the oxygen electrode side. Reported here are the oxidative treatment and dip-coating of carbon paper (Spectracarb™ 2050A-0850) with Nb-doped TiO2 sols (anatase phase) to increase the corrosion resistance of the carbon paper at the interface between catalyst layer and gas diffusion backing layer. Coating of carbon paper with Nb-doped TiO2 sols generates a reasonably uniform layer of TiO2 and covers the individual carbon fibers well only if the carbon paper is oxidatively functionalized prior to coating. This can be reasoned with a better wetting of the functionalized carbon paper by the sol-gel and the formation of covalent bonds between Ti and the large number of functional groups on the surface of oxidized carbon paper, which is in good agreement with previous observation for carbon nanotubes. The resistance towards oxidation of coated and uncoated samples of untreated and functionalized carbon paper was probed by cyclic voltammetry in 0.5 M aqueous H2SO4 at 1.2 V versus Ag/AgCl for up to 72 hours to mimic the conditions in a unitized regenerative fuel cell. Among these four cases studied here, functionalized carbon paper coated with a layer of Nb-doped TiO2 shows the highest stability towards electrochemical oxidation while uncoated functionalized carbon paper is the least stable due to the large number of available oxidation sites. These results clearly demonstrate that a coating of carbon fibers with TiO2 generates a lasting protection against oxidation under conditions encountered at the oxygen electrode side of unitized regenerative fuel cells.

The dynamic behavior of the three-phase interface on a platinum electrode during oxygen reduction (ORR) and oxygen evolution reactions (OER) in a potassium hydroxide droplet was studied by a charge-coupled device (CCD) and confocal laser microscopy. Contact angle measurements reveal a spreading interface during ORR, whereas the droplet figure remains unchanged during OER. The microscopy results demonstrated the formation of many fine droplets in the vicinity of the meniscus boundary during ORR, which was attributed to vapor condensation on the surface. Correlation of these observations with electrochemical data and differences in the results between ORR and OER suggest that the motion of the three-phase interface is induced by local pH and temperature gradients in the meniscus, presumably caused by ORR uniformity under the limitation of dissolved oxygen.

A novel direct carbon fuel cell is designed and fabricated using cathode-supported tubular solid oxide fuel cell technology, which makes the research and optimization of fuel electrode much easier. The maximum power density of a SO-DCFC (solid oxide direct carbon fuel cell) single cell is 172.7 and 91.1 mW cm−2 at 900 and 850 °C, respectively, with carbon as the fuel humidified nitrogen to initiate reforming reactions. Results show that the cathode supported tubular design may have future promise.

In this work a gas diffusion layer (GDL) prepared with metallic ceramics TIC for a unitized regenerative fuel cell (URFC) was first investigated By the measurements of morphological characteristic electrical conductivity absolute through-plane permeability and electrochemical stability the characteristics of the novel GDLs and the conventional one were compared A high corrosion-resistive and low-cost GDL with 80 wt % TiC and 20 wt % IrTiO(x) was expected to enhance the cycle performance of URFC And the total loading of Ir in the novel URFC was only 1 3 mg cm(-2) The URFC with the novel GDL exhibited the similar initial performance under both fuel cell and electrolysis modes as that using the conventional GDL. However the life cycle testing over 60 h showed that the URFC with the novel GDL was more stable than the URFC with the traditional GDL indicating that the GDL with TiC and IrTiO(x) was beneficial to improve the cycle life of the URFC (C) 2010 Elsevier Ltd All rights reserved

In this study a direct-mode fuel cell in which the fuel and electrolyte are mixed with each other is tested. An alkaline electrolyte is used. The aim was to develop a fuel cell which operates direc ...

In order to understand the origins of performance variations in unitized regenerative fuel cells (URFCs), bifunctional catalyst layers (BCLs) fabricated with two different methods, i.e., ink deposition on membrane or GDL. were designed in this paper. The performances of the two different methods were evaluated, and their reaction dynamics were measured by electrochemical impedance spectra. The different BCLs, caused by the different preparation processes, were found to influence the fuel cell performance. The cell potentials of the URFCs using platinum sprayed onto the gas diffusion layer (GDL) are above 0.100 V higher than those with platinum sprayed onto the membrane at 800 mA cm(-2) in fuel cell (FC) mode. The mass transport resistances of the URFCs at different operation modes were also compared. It was proved that the platinum layer formed by applying platinum onto the GDL could prevent the cell from water flooding in FC mode. However, it was found that the cell performance changed slightly in water electrolysis mode with different BCLs. The electron conduction path was also found to be hindered by an IrO(2) agglomerate, which led to a decrease in cell performance. The highest and lowest round-trip efficiencies of the URFC with different BCLs were 42.1% and 22.3%, respectively, at 800 mA cm(-2). (C) 2009 Elsevier Ltd. All rights reserved.

To find the best operating conditions and oxygen electrode catalyst of the PEM unitized regenerative fuel cell (URFC) system, we examined the effect of reaction conditions and the performance of several bifunctional electrocatalysts for oxygen electrode in a single cell PEM URFC system. When Pt black was employed for both electrodes, the URFC performance improved with increasing cell temperature up to 70 ◦ C and catalyst loading up to 6.7 mg cm −2 . Among the catalysts prepared in the present study for oxygen electrode, fuel cell performance decreased in the order of Pt black > PtIr > PtRuOx > PtRu ∼ PtIr > PtIrOx, whereas, water electrolysis performance decreased in the order of PtIr ∼ PtIrOx > PtRu > PtRuIr > PtRuOx ∼ Pt black, showing significant performance improvement by addition of second metals such as Ir or IrO x to Pt black. Consequently, PtIr had the best URFC performance with high round-trip efficiency and stability during the cycling operation of the URFC system. Therefore, PtIr is promising as an oxygen electrode of the PEM URFC system. © 2004 Elsevier Ltd. All rights reserved.

The RSPFC is a battery-like hydrogen/oxygen system which offers the possibility of splitting water by electrolysis, storing the gases hydrogen and oxygen and regenerating electricity by the fuel cell process. The most outstanding feature is the use of only one energy conversion device for both processes, electrolysis and fuel cell operation. Membrane technology is the most suitable system for realization of this concept. Basic investigations concerning the best catalysts for the electrode reactions at electrode/membrane units have been carried out. The preparation of these units and the electrochemical characterization by half cell measurements and impedance measurements are reported as well as first experiences in reversibly operating small single cells.