Proton Conducting Ceramic Fuel Cells

Much of the preceding discussion has concerned the development of SOFCs based on oxide ion conducting ceramics. In these devices the electrolyte, cathode and anode all possess significant levels of oxygen ionic conduction and materials selection is then a compromise between the demands of each functional layer. As an alternative proton conducting ceramics have been suggested as the basis for a lower temperature SOFC. In this instance protons are incorporated into the oxide via the following reaction  

Proton conducting ceramics are commonly based upon the perovs-kite structure type with the cerate and zirconate types being most prevalent. Initial studies focused on the SrCeOs- and SrZrOs-based materials. Uchida et al. demonstrated sizeable proton conductivity in each of these materials but due to concerns over the stability of these compositions attention shifted towards the Ba analogues. In these materials the key concern is their stability in CO2 containing atmospheres. 

1 Materials for Proton Conducting Solid Oxide Fuel Cells 

Proton conducting ceramic fuel cells are currently considered as constituting devices with an electrolyte component from the BaZrOs and 

INORGANIC MATERIALS FOR SOLID OXIDE FUEL CELLS 

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

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 ... 

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. 

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... 

Reduction of CO2 may also be done in a cell with a proton-conducting ceramic such as the perov-skite of the type BaZri-xYxOj as electrolyte [18]. Oxygen electrode is usually perovskites, and CO electrode is usually Ni-YSZ in similarity to SOEC, but recently ceramic fuel electrodes have been demonstrated [19]. The proton conduction is... 

At the university of Alberta in Canada, Fu et al. (2011) showed the possibility of cogenerating ethylene and electrical power by ethane dehydrogenation over a nano-Cr203 anode catalyst in a proton ceranfic fuel cell reactor having a BaCeOo.s.YOo os NdOo isOs-s (BCYN) perovskite oxide as proton-conducting ceramic electrolyte and Pt as cathode catalyst. The power density increased from 51 mW/cm to 118 mW/cm, and the ethylene yield increased from about 8% to 31% when the operating temperature of the solid oxide fuel cell reactor was increased from 650°C to 750°C. 

Since the type of electrolyte material dictates operating principles and characteristics of a fuel cell, a fuel cell is generally named after the type of electrolyte used. For example, an alkaline fuel cell (AFC) uses an alkaline solution such as potassium hydroxide (KOH) in water, an acid fuel cell such as phosphoric acid fuel cell (PAFC) uses phosphoric acid as electrolyte, a solid polymer electrolyte membrane fuel cell (PEMFC) or proton exchange membrane fuel cell uses proton-conducting solid polymer electrolyte membrane, a molten carbonate fuel cell (MCFC) uses molten lithium or potassium carbonate as electrolyte, and a solid oxide ion-conducting fuel cell (SOFC) uses ceramic electrolyte membrane. 

Smirnova, A., Prakash, R, Phillips, R. and Sammes, N.M. (2(K)4) Electrolyte proton-conductive materials for protonic ceramic fuel cells (PFCFs). Proceedings of the sixth European Solid Oxide Fuel Cell Forum, 28 June to 2 July 2004,... 

Higgins, S., Sammes, N. and Smirnova, A. (2005), Proton-conductive electrolyte materials for protonic ceramic fuel cells (PCFCs), Proc. of the ninth international symposium on solid oxide fuel cells (SOFC-IX), Eds., S.C. Singhal and J. Mizusaki, Vol. 2, pp. 1149-1155. The Electrochemical Society Inc., Pemiington, NJ, USA. 

A broader, more generie name for fuel eells operating at the temperatures described in this seetion would be "ceramie" fuel eells. The electrolyte of these eells is made primarily from solid ceramie material to smvive the high temperature environment. The eleetrolyte of present SOFCs is oxygen ion conducting. Ceramic cells eould also be proton eonducting. 

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... 

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