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  Electrode for electrochemical cell and electrochemical cellUSPTO Application #: 20070080058Title: Electrode for electrochemical cell and electrochemical cell Abstract: At this time, the resultant protons (H+) and electrons (e−) exist in the anode 3. The subsequent electrode reaction is completed after the protons travel to an electrolyte 2 and the electrons travel to a lead 5. The reverse reaction occurs at a cathode 4 to generate hydrogen gas. H2→2H++2e− The following reaction occurs at the interface between a gas phase and an anode 3: To provide low-overpotential electrodes for an electrochemical cell including a proton-conductive electrolyte and an electrochemical cell including the electrodes. (end of abstract) Agent: Birch Stewart Kolasch & Birch - Falls Church, VA, US Inventors: Hiroshige Matsumoto, Hitoshi Takamura, Junichiro Mizusaki, Tatsuya Kawada, Keiji Yashiro USPTO Applicaton #: 20070080058 - Class: 204291000 (USPTO) Related Patent Categories: Chemistry: Electrical And Wave Energy, Apparatus, Electrolytic, Elements, Electrodes, Composition The Patent Description & Claims data below is from USPTO Patent Application 20070080058. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention relates to electrodes for an electrochemical cell including a proton-conductive electrolyte and electrochemical cells, and particularly relates to electrodes and electrochemical cells suitable for high-temperature proton-conductive electrolytes. BACKGROUND ART [0002] Hydrogen has recently come under the spotlight as an energy source for fuel cells etc. in view of global environment conservation and energy saving. Accordingly, as is well known, proton-conductive electrolytes have been widely researched as electrochemical devices useful for hydrogen separation, which is an essential technology for the production of hydrogen, and fuel cells. [0003] Proton-conductive electrolytes are electrolyte materials containing positive hydrogen ions, namely protons, as a mobile ion species. Protons can move in the electrolytes when a voltage is applied. If, therefore, gas electrodes are provided on a proton-conductive electrolyte (hereinafter referred to as a proton-conductive cell), a direct current may be allowed to flow through the cell to achieve hydrogen separation or hydrogen fuel cell power generation according to the type of gas in contact with the electrodes. [0004] Gas electrodes of a proton-conductive cell serve to produce hydrogen-involved electrode reactions. The voltage required as the driving force for the electrode reactions is called electrode overpotential. A lower electrode overpotential allows the proton-conductive cell to operate more efficiently; therefore, materials with lower electrode overpotentials are demanded to achieve higher-performance gas electrodes. [0005] Examples of conventional materials for gas electrodes include porous electron-conductive materials and cermets of electron-conductive materials and electrolytes. Such electrodes are designed exclusively to transfer electrons. For example, techniques for hydrogen separation devices having some type of high-temperature proton conductor as a proton-conductive electrolyte have been proposed (for example, Hiroyasu Iwahara, Solid State Ionics, 125, 271-278(1999)). [0006] Non-Patent Document 1: Hiroyasu Iwahara, Solid State Ionics, 125, 271-278(1999) [0007] According to this technique, the electrodes used are porous platinum electrodes. In this case, it is obvious that platinum is used as an electron-conductive material. If electrodes that serve only to transfer electrons are used for proton-conductive electrolytes, some electrolytes, unfortunately, cause slow hydrogen-involved electrode reactions which result in high electrode overpotential; that is, they require a large electrical energy in order to cause the electrode reactions. In fact, perovskite proton conductors containing zirconium (Zr) that have conventional porous platinum electrodes exhibit extremely poor electrode properties, as shown in Examples below as comparative examples. DISCLOSURE OF INVENTION Problems to be Solved by the Invention [0008] To solve the above problem, the present invention provides low-overpotential electrodes for electrochemical cells including a proton-conductive electrolyte and an electrochemical cell including the electrodes. Means for Solving the Problems [0009] As a result of intensive studies, the present inventor has found and confirmed by experiment that a lower electrode overpotential can be achieved using electrodes that function not only to transfer electrons but also to include protons or hydrogen, thereby completing the following invention: [0010] (1) Electrodes for an electrochemical cell including a proton-conductive electrolyte. The electrodes are an anode and a cathode, and the anode and/or the cathode is made of a solid having hydrogen permeability. [0011] The reactions at gas electrodes are the reactions among hydrogen or a hydrogen-containing compound in a gas, protons, and electrons. These electrode reactions proceed at sites where the three components coexist. Such reaction sites are called three-phase interfaces since the three components usually exist separately as a gas phase, an electrolyte phase, and an electron conductor phase, respectively. [0012] Although the three-phase interfaces should extend only in one dimension in view of their components, the reaction sites where the electrode reactions can occur must extend in at least two dimensions. Accordingly, it is considered that the reaction sites where the electrode reactions can occur actually have some extension at the interface between the gas phase and the electron conductor phase and/or the interface between the gas phase and the electrolyte phase in the vicinity of the three-phase interfaces. For the former combination, some reaction intermediate associated with hydrogen occurs at the interface between the gas phase and the electron conductor phase, and the electrode reactions can proceed through the intermediate. For the latter, on the other hand, the electrode reactions occur probably because the electrolyte phase, which has no inherent electron permeability, exhibits electron permeability to some extent locally at the interface with the gas phase in the vicinity of the electron conductor phase. [0013] The performance of gas electrodes (that is, the magnitude of electrode overpotential) depends on the quantity (area) of three-phase interfaces and the smoothness of the electrode reactions occurring at the three-phase interfaces in a particular quantity (catalytic properties). The performance of the gas electrodes should therefore be achieved by increasing the three-phase interfaces and/or the catalytic properties per unit three-phase interface. [0014] According to the present invention, the anode and/or the cathode is made of the "solid having hydrogen permeability" so that it can function not only to transfer electrons but also to include protons or hydrogen. This allows the interfaces between the electrodes and the gas phase to function as electrode reaction sites and thus provide a lower electrode overpotential. [0015] (2) The electrodes according to Item (1). In this item, the proton-conductive electrolyte has a perovskite structure represented by the general formula AB.sub.xO.sub.3-d (wherein 0.8.ltoreq.x.ltoreq.1.2); and the B-site elements include zirconium (Zr). [0016] Although the electrodes according to the present invention may in principle be used in combination with any type of proton-conductive electrolyte, they are effective particularly for electrolytes having a perovskite structure including zirconium (Zr) as a B-site element. [0017] High-temperature proton conductors are broadly divided into cerates including Ce as a B-site element and zirconates including Zr as a B-site element. In general, cerate-based electrolytes feature high conductivity but exhibit poor chemical stability and mechanical strength while zirconate-based electrolytes exhibit lower conductivity than cerates but feature excellent stability and strength. Although the introduction of Zr as a B-site element increases the resistance of the electrolyte, it allows the electrolyte to have a smaller thickness because of the high mechanical strength. [0018] (3) The electrodes according to Item (2) above. In this item, the content of zirconium (Zr) in the B-site elements is 20 mole percent or more. [0019] As described above, the chemical stability of proton-conductive electrolytes increases with increasing content of zirconium. It is known that, if proton-conductive electrolytes including barium (Ba) as an A-site element, particularly, contain 20 mole percent or more of zirconium, they are stable with no reaction even against 100% carbon dioxide. Continue reading... Full patent description for Electrode for electrochemical cell and electrochemical cell Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Electrode for electrochemical cell and electrochemical cell patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Electrode for electrochemical cell and electrochemical cell or other areas of interest. ### Previous Patent Application: Plating apparatus, plating cup and cathode ring Next Patent Application: Sputtering device Industry Class: Chemistry: electrical and wave energy ### FreshPatents.com Support Thank you for viewing the Electrode for electrochemical cell and electrochemical cell patent info. 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