An electrochemical cell includes a fuel electrode, an air electrode containing a perovskite type oxide as a main component, the perovskite type oxide being represented by a general formula ABO.sub.3 and containing La and Sr at the A site, and a solid electrolyte layer arranged between the fuel electrode and the air electrode. The air electrode includes a first portion and a second portion, the first portion being located on the most upstream side in a flow direction of an oxidant gas that flows through a surface of the air electrode, the second portion being located on the most downstream side in the flow direction. A first ratio of a La concentration to a Sr concentration detected at the first portion through Auger electron spectroscopy is at least 1.1 times a second ratio of a La concentration to a Sr concentration detected at the second portion through Auger electron spectroscopy.

An electrochemical reaction unit including a unit cell, a cathode-side member, and an anode-side member. The sum La of the distance Lai between a virtual straight line representing a center position of the unit cell and the midpoint between opposite end points of a cathode-side supply opening group and the distance Lao between the virtual straight line and the midpoint between opposite end points of a cathode-side discharge opening group is smaller than the sum Lf of the distance Lfi between the virtual straight line and the midpoint between opposite end points of an anode-side supply opening group including an opening of an anode-side supply communication channel and the distance Lfo between the virtual straight line and the midpoint between opposite end points of an anode-side discharge opening group including an opening of an anode-side discharge communication channel.

An electrochemical reaction unit including a unit cell, a cathode-side member, and an anode-side member. The sum La of the distance Lai between a virtual straight line representing a center position of the unit cell and the midpoint between opposite end points of a cathode-side supply opening group and the distance Lao between the virtual straight line and the midpoint between opposite end points of a cathode-side discharge opening group is smaller than the sum Lf of the distance Lfi between the virtual straight line and the midpoint between opposite end points of an anode-side supply opening group including an opening of an anode-side supply communication channel and the distance Lfo between the virtual straight line and the midpoint between opposite end points of an anode-side discharge opening group including an opening of an anode-side discharge communication channel.

A solid oxide electrolyzer electrolyte composition includes a scandia and ceria stabilized zirconia, containing 5 to 12 mol % scandia, 1 to 7 mol % ceria, and 80 to 94 mol % zirconia, or a yttria and ceria stabilized zirconia containing 3 to 10 mol % yttria, 1 to 6 mol % ceria, and 84 to 96 mol % zirconia.

An electrolyte of a solid oxide cell is required to be capable of suppressing both gas cross-leak and electron leak. In addition, it is important from the viewpoint of a reduction in material costs and in the electric resistance of the electrolyte that the electrolyte is made into a thin film and that no expensive noble metal is used. The present invention provides a thin-film-shaped proton conducting electrolyte capable of suppressing both gas cross-leak and electron leak, a solid oxide cell using the proton conducting electrolyte, and a manufacturing method for the proton conducting electrolyte and the solid oxide cell. A proton conducting electrolyte using an oxide material having proton conductivity is provided. The proton conducting electrolyte includes a first portion containing Me (Me=at least any one of Ti, Mn, Fe, Co, Ni, and Cu), and a second portion different in Me content from the first portion.

An object of the present invention is to provide a fuel cell that obtains high output density and prevents stress application to the cell during stack assembling and breakage. The fuel cell is equipped with a unit cell including a structure in which an electrolyte layer is sandwiched between an anode electrode layer and a cathode electrode layer. The unit cell is disposed between a first member and a second member. An intermediate substrate is disposed between the first member and the second member. The unit cell is supported at the outer peripheral portion thereof by the intermediate substrate. The width of the electrolyte layer is the maximum width or less of a hollow portion formed between at least one of the first member and the second member and the unit cell.

An object of the present invention is to provide a fuel cell that obtains high output density and prevents stress application to the cell during stack assembling and breakage. The fuel cell is equipped with a unit cell including a structure in which an electrolyte layer is sandwiched between an anode electrode layer and a cathode electrode layer. The unit cell is disposed between a first member and a second member. An intermediate substrate is disposed between the first member and the second member. The unit cell is supported at the outer peripheral portion thereof by the intermediate substrate. The width of the electrolyte layer is the maximum width or less of a hollow portion formed between at least one of the first member and the second member and the unit cell.

The invention discloses a method and device for detecting a leakage rate of a solid oxide fuel cell system on line. The method comprises steps of: cutting off fuel gas supply of an anode cavity, cutting off an exhaust line of the anode cavity and cutting off high-pressure air supply of a cathode cavity in the operation process of a solid oxide fuel cell; obtaining an open-circuit voltage and temperature of the solid oxide fuel cell; and determining a leakage rate of the solid oxide fuel cell system according to the open-circuit voltage and the temperature of the solid oxide fuel cell. Based on the technical solutions disclosed by the invention, the leakage rate of the solid oxide fuel cell system can be detected on line.

The invention discloses a method and device for detecting a leakage rate of a solid oxide fuel cell system on line. The method comprises steps of: cutting off fuel gas supply of an anode cavity, cutting off an exhaust line of the anode cavity and cutting off high-pressure air supply of a cathode cavity in the operation process of a solid oxide fuel cell; obtaining an open-circuit voltage and temperature of the solid oxide fuel cell; and determining a leakage rate of the solid oxide fuel cell system according to the open-circuit voltage and the temperature of the solid oxide fuel cell. Based on the technical solutions disclosed by the invention, the leakage rate of the solid oxide fuel cell system can be detected on line.

A fuel cell system includes at least one of plural electrochemical pump separators to separate carbon dioxide from a fuel exhaust stream or a combination of a gas separator and a fuel exhaust cooler located outside a hotbox.