Single Chamber Fuel Cell Research Articles

Performance of Surface Ionic Conduction Single Chamber Fuel Cell Prepared by the Sol Gel Method

Performance of Surface Ionic Conduction Single Chamber Fuel Cell Prepared by the Sol Gel Method

Voltage Oscillations in Single‐Chamber Fuel Cells Operating under a C3H8/O2 Mixture

AbstractSingle‐chamber fuel cells (SCFCs) are an alternative way to conventional SOFCs. Effectively, they do not require any more sealing between anodic and cathodic compartment's as the cell is fed with a mixture of hydrocarbon and oxygen. This paper deals with voltage oscillations observed with an SCFC composed of GDC (Ce0.9Gd0.1O1.95) supported electrolyte, Ni‐GDC anode and a BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3–δ) cathode, operating in the temperature range 500–600 °C and under various propane and oxygen mixtures, with a C3H8/O2 ratio between 0.2 and 0.66. Electrical and Thermo‐Programmed Oxidation (TPO) measurements combined with SEM observations allowed us proving that these oscillations are due to carbon nanowires deposition/oxidation cycles. A mechanism is proposed to explain this behavior.

Performance of Single Chamber Fuel Cell using an Inorganic Proton Conductor Prepared by Sol-Gel Method

Performance of a novel single chamber fuel cell (SCFC) using an inorganic proton conductor was studied to electric characteristic at catalytic electrodes and operating temperatures in dry gas mixtures of hydrogen and oxygen. The inorganic proton conductor of SCFC was prepared by the sol-gel method using the boehmite (AlO(OH)) material. The open-circuit voltage (OCV) of single cell achieved a maximum of 730mV in the dry gas mixtures of H2/O2=50% at room-temperature operation so that the impedance values of the single cell became lower when using the sputtered Pt as outer electrode and Pt paste as inner electrode. This OCV value corresponds to about theoretical electromotive force. The operating temperature of single cell could improve to 60°C by performing heat treatment of boehmite film covered with a nafion dispersion solution. Moreover, the power and current densities of single cell increased to 1.1mW/cm2 and 7.64mA/cm2 by making thin boehmite film of 3μm. As a result, the SCFC using the boehmite electrolyte prepared by sol-gel method were found to achieve the cell performance of high-energy density at higher operating temperatures in the dry gas mixtures such that it used as the portable electrochemical generator.

アルミナ膜をプロトン伝導体に用いた単室型燃料電池の交流インピーダンス法による抵抗特性

The resistance property of a single chamber fuel cell (SCFC) using a boehmite inorganic electrolyte as the proton conductor was studied by using alternating-current impedance method at room temperature operation (RT) in the dry gas mixtures of hydrogen and oxygen. The open circuit voltage (OCV) and maximum current density of SCFC using the Pt/CB electrode as anode and the Au or Pt electrodes as cathode were attained 776-690 mV and 0.13-0.17 mA/cm2. The cell resistance of SCFC using the Pt electrode became smaller value as compared with that using the Au electrode. The OCV of SCFC corresponded to a development index of polymer electrolyte fuel cell (PEFC), although the current density became lower than that of PEFC.

Separator-free fuel cell stacks operating in a mixture of hydrogen and air

Fuel cells for vehicular and residential applications have encountered a key technical challenge in cost reduction. This challenge can be avoided by operating a fuel cell stack without the use of gas separators, which are expensive and voluminous and therefore comprise a significant portion of the cost of a fuel cell stack. Single-chamber fuel cells (SCFCs) have the potential of realizing such operation, because there is no need for separation between fuel and air. In this paper, we present a selective anode (PtAu/C) and cathode (Pr-doped Mn2O3/C) for respective electrochemical hydrogen oxidation and oxygen reduction reactions in a SCFC. A single cell with these electrodes operated at 50 °C generated an open-circuit voltage of 1204 mV and a peak power density of 50 mW cm−2 in a feed mixture of 80% hydrogen and 20% air at a flow rate of 30 mL min−1. The high selectivity of these electrodes also enabled the design of two different separator-free fuel cell stacks, parallel and perpendicular to the gas stream. Both cell stacks exhibited increasing stack voltage and power output almost proportionally to the increase in the number of single cells. These results demonstrate that the separator-free fuel cell stack shows high potential for a significant reduction of the cost of fuel cell systems.

Low Temperature Operation of Single Chamber Fuel Cell Using BaCeO3 Electrolyte Film as Proton Conductor Grown by Helicon Plasma Sputtering

Thin film single chamber solid oxide fuel cell (SC-SOFC) with Barium Cerium Oxide (BaCeO3) electrolyte film as proton conductor, grown by the helicon plasma sputtering, was studied to determine the power generation property at lower operating temperatures between 200 and 400°C in the gas mixtures of hydrogen and oxygen. An SC-SOFC with a BaCeO3 electrolyte film thickness of 5 μm could be operated at 400°C in the gas mixtures of hydrogen and oxygen and had a maximum open circuit voltage of 455 mV. However, a V-I property at 400°C of SC-SOFC was considerably poor as a development index of SOFC, because the cell resistance with a several kΩ was due mainly to the interface reaction resistance of between the Pt catalytic electrodes and an amorphous electrolyte film.

Operating Temperature Property of Single Chamber Fuel Cell Appling an Alumina Evaporated Film to Proton Conductor

Operating Temperature Property of Single Chamber Fuel Cell Appling an Alumina Evaporated Film to Proton Conductor

Room temperature operation of surface‐conduction single chamber fuel cell using a novel inorganic electrolyte as proton conductor

AbstractThe performance at room temperature of a single chamber fuel cell (SCFC) using a novel pseudboehmite (pb) proton conductor as the inorganic electrolyte, which can operate in the gas mixtures of hydrogen and oxygen, is studied based on the dependence on the soaked treatments of the pb electrolyte, generated from the aluminum film. The surface‐conduction SCFC with a new electrode arrangement, moreover, operated at room temperature in the dry and wet gas mixtures. Maximum open circuit voltage (OCV) of 540 mV was achieved at room temperature operation in the wet gas mixture using the pb electrolyte generated by the soaked treatment of 60 °C. The OCV property in the dry gas mixture falls by a half value when compared to the case of the wet gas mixtures. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Electrode Performance of Nanostructured La1-aSraCo1-bFebO3-x on a Ce0.8Sm0.2O2 Electrolyte Prepared by Citrate-Nitrate Auto-Combustion

Nanostructured La1-aSraCo1-bFebO3-x (a=0.3-0.5; b=0-0.2) and Ce0.8Sm0.2O2 powders were successfully prepared by citrate- nitrate auto-combustion synthesis and were characterized by scanning electron microscopy and X-ray diffraction analysis. Electrochemical Impedance Spectroscopy measurements on symmetric cells were performed to evaluate the applicability of La1-aSraCo1-bFebO3-x as a cathode material for Single Chamber Solid Oxide Fuel Cells. Our results demonstrated that strontium has a positive effect while iron shows a slightly negative effect on the interfacial resistance. The effect of the electrode sintering temperature was investigated by varying the temperature from 850 {degree sign}C to 1250 {degree sign}C and the best sintering temperature was found to be 900 {degree sign}C. The best characteristics as cathode around the operating temperature of Single Chamber Fuel Cells were found for the composition with a=0.4 and the minimum iron doping; at 700{degree sign}C, an Area Specific Resistance of 0.13 ohm•cm2 was measured.

Recent advances in single-chamber fuel-cells: Experiment and modeling

Single-chamber fuel cells (SCFC) are ones in which the fuel and oxidizer are premixed, and selective electrode catalysts are used to generate the oxygen partial pressure gradient that in a conventional dual-chamber design is produced by physical separation of the fuel and oxidizer streams. SCFCs have been shown capable of generating power densities above 700 mW/cm 2 with appropriate catalysts, making them potentially useful in many applications where the simplicity of a single gas chamber and absence of seals offsets the expected lower efficiency of SCFCs compared to dual-chamber SOFCs. SCFC performance is found to depend sensitively on cell microstructure, geometry, and flow conditions, making experimental optimization tedious. In this paper, we describe recent work focused on developing a quantitative understanding the physical processes responsible for SCFC performance, and the development of an experimentally-validated, physically-based numerical model to allow more rational design and optimization of SCFCs. The use of the model to explore the effects of fuel/oxidizer ratio, anode thickness, and flow configuration is discussed.

Compatibility of screen-printing technology with micro-hotplate for gas sensor and solid oxide micro fuel cell development

Screen-printing technology is widely used in the field of gas sensors and can also be used to fabricate electrodes for solid oxide fuel cell (SOFC). The compatibility of this technique with micro-hotplate is studied to produce micro sensors and micro SOFC. For sensors application, development of inks containing precursor of sensing element allows to decrease annealing temperature and to improve adhesion. For SOFC development, we investigated a new type of device named single-chamber fuel cell (SCFC) for which the fuel and the oxygen are mixed and in contact with both the anode and cathode. Such devices were firstly built at a millimeter scale using LSM for cathode, YSZ for electrolyte and Ni-YSZ cermet for anode. Two types of configuration were studied: SCFC developed on YSZ support with screen-printed electrodes, and SCFC entirely manufactured by screen-printing on a inert ceramic substrate made of alumina. Although weak power densities were measured, around 1 mW/cm 2, the feasibility of SCFC was confirmed. Then, preliminary results concerning LSM cathode deposition on micro-hotplate were obtained. LSM layers annealed up to 800 °C resist well to temperature cycling but exhibit low conductivity.

Development of a planar SOFC device using screen-printing technology

The aim of this study is to investigate the potentialities of screen-printing technology to manufacture planar SOFC device. Widely studied materials were chosen for this work, particularly YSZ as electrolyte, LSM as cathode and Ni-YSZ cermet for the anode. This technique was firstly used to elaborate the porous electrodes and the collectors constituted by a gold grid. These layers were deposited onto sintered YSZ pellets and two types of fuel cells were produced: conventional two-chambers devices where anode and cathode atmospheres are separate and single-chamber fuel cells (SCFC) where the electrodes are deposited on the same electrolyte side and are in contact with a common surrounding atmosphere. Two test benches were developed to study the cells’ performances in separate hydrogen/oxygen atmospheres for conventional device or in a unique methane/oxygen mixture for single-chamber device. At this point of the study, performances are not optimized and weak power density is available, around 1.2 mW/cm 2 for SCFC at 800 °C with a ratio of methane to oxygen equal to 1.5. Performances of two-chambers devices are also weak due to the electrolyte thickness around 1 mm and the low experimental temperature, 500 °C. However, the results confirm the feasibility of SCFC and developed test benches constitute a tool for further investigations of modified devices, especially with YSZ electrolyte thick film supported on interconnect materials as no tightness is required for SCFC, or with multi-layered electrodes.

A Two-Dimensional Model of a Single-Chamber SOFC with Hydrocarbon Fuels

The single chamber fuel cell (SCFC) is a novel simplification of the conventional solid oxide fuel cell (SOFC) into which a premixed fuel/air mixture is introduced. It relies on the selectivity of the anode and cathode catalysts to generate a chemical potential gradient across the cell. For SCFC running on hydrocarbon fuels, the anode catalyst promotes in-situ internal reforming of the hydrocarbon and electrochemical oxidation of the syngas, while the cathode catalyst reduces oxygen simultaneously. Laboratory tests of small designs of such fuel cells have demonstrated excellent electrical performance (1, 2).

Anode-supported thin-film fuel cells operated in a single chamber configuration 2T-I-12

The performance characteristics of anode-supported, thin-film, single chamber fuel cells (SCFCs) have been investigated. Cells, in which Ni+Sm 0.15Ce 0.85O 2 (Samaria doped ceria, SDC) served as the anode and SDC as the electrolyte, were fabricated by dry pressing. High quality, bilayer structures with electrolyte thicknesses as small as 10 μm were prepared with excellent reproducibility. The cathode, 70 wt.% Sm 0.5Sr 0.5CoO 3+30% SDC, was deposited by a spray method. The cells were operated in a dilute propane+oxygen mixture. The influence of environmental temperature, gas composition and flow rate on the fuel cell performance were investigated. At low temperatures, fuel cell power output was limited primarily by poor catalytic activity at the anode whereas at high temperatures it was limited primarily by high catalytic activity of the cathode towards propane oxidation. Thus, intermediate temperatures are optimal for maximizing power densities. An increase in fuel flow rate led to an increase of the fuel cell temperature due to exothermal partial oxidation on the anode, producing a complex response in fuel cell power output. Under optimized gas compositions and flow conditions, a peak power density of ∼210 mW/cm 2 was obtained.

Single Chamber Fuel Cells: Flow Geometry, Rate, and Composition Considerations

Single Chamber Fuel Cells: Flow Geometry, Rate and Composition Considerations Ionel C. Stefan, ∗ Craig P. Jacobson, Steven J. Visco, Lutgard C. De Jonghe Lawrence Berkeley National Laboratory 1 Cyclotron Rd, Berkeley, CA 94720 ABSTRACT Four different single chamber fuel cell designs were compared using propane-air gas mixtures. Gas flow around the electrodes has a significant influence on the open circuit voltage and the power density of the cell. The strong influence of flow geometry is likely due to its effect on gas composition, particularly on the oxygen chemical potential at the two electrodes as a result of gas mixing. The chamber design which exposes the cathode first to the inlet gas was found to yield the best performance at lower flow rates, while the open tube design with the electrodes equally exposed to the inlet gas worked best at higher flow rates. INTRODUCTION Single chamber fuel cells (SCFCs) have no seal separating the anode and cathode, and consequently both electrodes are simultaneously exposed to the fuel/air mixture. Although SCFCs were proposed more than four decades ago, 1,2 only recently have these devices surpassed the level of laboratory curiosity by achieving electrode power densities comparable to those of the much more studied dual chamber, sealed cells. 3,4 While the SCFC research is still at an early stage, new applications are emerging, such as simple low-power sources 5 and hydrocarbon sensors. 6 The principle of operation for a single chamber fuel cell is based on the different electrocatalytic properties of fuel cell electrodes toward anodic oxidation of fuel and cathodic reduction of oxygen, respectively, thus resulting in an EMF even in a uniform atmosphere containing E-mail: CIStefan@lbl.gov