Fuel cell protonic ceramic

Dr. Hui has worked on various projects, including chemical sensors, solid oxide fuel cells, magnetic materials, gas separation membranes, nanostruc-tured materials, thin film fabrication, and protective coatings for metals. He has more than 80 research publications, one worldwide patent, and one U.S. patent (pending). He is currently leading and involved in several projects for the development of metal-supported solid oxide fuel cells (SOFCs), ceramic nanomaterials as catalyst supports for high-temperature PEM fuel cells, protective ceramic coatings on metallic substrates, ceramic electrode materials for batteries, and ceramic proton conductors. Dr. Hui is also an active member of the Electrochemical Society and the American Ceramic Society. 

Several types of fuel cell are currently under development, using different electrolyte systems phosphoric acid (PAFC), alkaline, molten carbonate (MCFC), regenerative, zinc-air, protonic ceramic, (PCFC), proton exchange membrane (PEM), direct methanol (DMFC), and solid oxide (SOFC). The last four contain solid electrolytes. 

Protonic ceramic fuel cell (PCFC)—The ceramic electrolyte can elec-trochemically oxidize fossil fuels, eliminating the need for fuel reformers. 

Development of compact fuel cells, created by combining proton conductive perovskite-type oxide ceramics with metal-hydride materials, has been already proposed [1], Our group expects that the compact fuel cells can be utilized under radiation environments such as fission and fusion reactors or cosmic [2], Therefore, it is very important to understand behaviors of electron and proton conductions under radiation environments. 

Advances in fuel cells were later accelerated by space and defense programs. Fuel cells found initial practical application with the Gemini (1962-1966) and the Apollo (1968-1972) spacecraft missions, and are still used to provide water and electricity for the Space Shuttle. The upgrade in fuel cell performance over the last four decades has been based on the development of new proton-conducting polymers, like Nafion and Gore-tex , ceramics and catalysts, as well as on greater insights into... 

Porous membranes, especially ceramic and carbon compositions, are the focus of intense development efforts. Perhaps, the least studied of the group, at least for hydrogen separations, are the ion-conducting membranes (despite the fact that many fuel cells incorporate a proton-conducting membrane as the electrolyte), and this class of membranes will not be discussed further in this chapter. 

DIRECT ENERGY CONVERSION BY PROTON-CONDUCTING CERAMIC FUEL CELL SUPPLIED WITH CH4 AND ILO AT 60()-8()()°C... 

Relations between current density and terminal voltage (I-V curves) of the proton-conducting ceramic of Sr( c were determined for application to a fuel cell working at 600 - 800°C. In... 

Keywords proton-conducting ceramic, Sr-Ce-Yb oxide, fuel cell, high temperature, CH steam reforming, internal reform. 

Figure 8. Mass and charge transfer on proton-conducting ceramics fuel cell...

Figure 8 shows a schematic illustration of the anode reaction in the present proton-conducting ceramic fuel-cell system. In the anode, the following reactions may occur simultaneously ... 

On the other hand, the largest disadvantage is that the protonic resistance of the Sr-Ce-Yb oxide was comparatively larger than that of a polymer-electrolyte-membrane fuel cell (PEM-FC) and was comparable with 0 ion conductivity of an yttria-stabilised zirconia (YSZ). Consequently, as seen in Figs. 4 and 5, the current density through the Sr-Ce-Yb oxide fuel cell was order of niA/cni and was much smaller than that of PEM-FC. This is because a thin ceramic is very difficult to manufacture. The protonic conductivity of the Sr-Ce-Yb oxide itself was around one-tenth smaller than that of PEM. Moreover, the conductivity was order of 10 " S/cm when a CH4 and HjO mixture was supplied directly to the cell without external reformer. The overall conductivity became around 10 -fold less than that of PEM, because the rate-controlling step was in the steam-reforming reaction. 

The I-V curves for the fuel-cell system composed of a SrCeo gsYbo osOs-a ceramic electrolyte and Ni/SiO2 porous electrodes were determined under the conditions of CH4 + H2O and H2 + H2O supplies, and the values of Eg and a were correlated to a function of temperature and the anode H2O partial pressure. The Eg values were consistent with the Nernst equation. It was found that Eg was a good indication of Ph2 generated on the anode electrode when the CH4 and H2O mixture was introduced into the anode. The o values determined included the two contributions of the protonic conductivity of the... 

In proton exchange membrane fuel cells, perhaps the most divulgate type of fuel cells, a proton-conducting polymer membrane acts as the electrolyte separating the anode and cathode sides. Porous anaodic alumina (Bocchetta et al., 2007) and mesoporous anastase ceramic membranes have been recently introduced in this field (Mioc et al., 1997 Colomer and Anderson, 2001 Colomer, 2006). 

At present, a great deal of research is being devoted to the development of intermediate-temperature protonic ceramic fuel cells (IT-PCFCs), which can simultaneously produce value-added chemicals and electrical power [93, 94]. As shown schematically in Figure 12.19, proton conduction implies that water vapor is produced at the cathode, where it is swept away by air (in contrast to the SOFC, where it dilutes the fuel). Consequently, with a purely protonic electrolyte and... 

Bridging the temperature gap with proton-conducting ceramics Direct ammonia fuel cells... 

A simple method to prepare the membrane is to react directly fluorosulfonyl difluoroacetyl fluoride, FS02CF2C0F, with lithium bis(trimethylsilyl)-amide, (CH3)3SiNLiSi(CH3)3, and to cross-link with multivalent cations.209 Furthermore, ceramic membranes (P205-Si02 glass membrane) prepared by the sol-gel method have been examined as proton conducting electrolytes for fuel cells.210... 

Protonated Chalcogenide Materials for Fuel Cell Electrolyte Membranes, poster at the 104th Annual Meeting and Exposition of the American Ceramic Society, Steve W. Martin, Steven A. Poling, and Jacob T. Sutherland, St. Eouis, MO, April 29-May 1, 2002. 

Our approach is to separate the conduction paths for H+ ions and electrons through the incorporation of a ceramic second phase. This approach essentially eliminates the combined dependence of hydrogen flux on electronic and proton conductivities. The approach is to short-circuit the electron flow-paths so that the overall flux is limited only by the proton conductivity. A similar mixed conducting requirement exists for electrodes in high-temperature proton conducting fuel cells, and some work has been carried out to develop mixed conductors as electrodes [24]. 

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