A fuel cell unit structure includes: power generation cells; separators; a flow passage portion formed between the separators and including flow passages configured to supply gas to the power generation cells; gas flow-in ports configured to allow the gas to flow into the flow passage portion; gas flow-out ports configured to allow the gas to flow out from the flow passage portion; and an adjustment portion configured to adjust an amount of the gas flowing through the flow passages. The adjustment portion includes a first auxiliary flow passage provided between the power generation cells arranged to be opposed to each other on a same plane with a gas flow-in port of the gas flow-in ports being located on an extended line of an extending direction of the first auxiliary flow passage.

A single fuel cell according to the present disclosure includes a power generation section, a power non-generation section which does not include the power generation section, and an oxygen-ion-insulating gas seal film arranged so as to cover the surface of the power non-generation section, and the gas seal film is configured by a structure formed by firing a material containing MTiO.sub.3 (M: alkaline earth metal element) and metal oxide. The structure may include a first structure and a second structure which are different in composition, the first structure may include components derived from MTiO.sub.3 in larger amounts than the second structure, the second structure may include a metal element contained in the metal oxide in a larger amount than the first structure, and the area ratio of the second structure in the structure may be not less than 1% and not more than 50%.

A single fuel cell according to the present disclosure includes a power generation section, a power non-generation section which does not include the power generation section, and an oxygen-ion-insulating gas seal film arranged so as to cover the surface of the power non-generation section, and the gas seal film is configured by a structure formed by firing a material containing MTiO.sub.3 (M: alkaline earth metal element) and metal oxide. The structure may include a first structure and a second structure which are different in composition, the first structure may include components derived from MTiO.sub.3 in larger amounts than the second structure, the second structure may include a metal element contained in the metal oxide in a larger amount than the first structure, and the area ratio of the second structure in the structure may be not less than 1% and not more than 50%.

A cell according to the present disclosure includes: a solid electrolyte layer including a first surface and a second surface opposite to the first surface; a fuel electrode on the first surface; an air electrode on the second surface; and a middle layer between the second surface and the air electrode. The middle layer=is a CeO.sub.2-type sintered body containing Si, the content of Si equivalent to or less than 150 ppm in terms of SiO.sub.2. A cell stack device includes a cell stack in which the plurality of cells is aligned. A module includes: a storage container; and the cell stack device that is housed in the storage container. A module housing device includes: an external case; the module and an auxiliary equipment that drives the module, which are housed in the external case.

A fuel cell stack comprises: a substrate; a plurality of single fuel cells each of which includes a fuel side electrode, an electrolyte, and an oxygen side electrode deposited on the substrate; an interconnector film electrically connecting the fuel side electrode of one single fuel cell of adjacent single fuel cells of the plurality of single fuel cells and the oxygen side electrode of the other single fuel cell; and a porous ceramic film covering at least the interconnector film in a region between a first fuel side electrode of one single fuel cell of adjacent single fuel cells and a second fuel side electrode of the other single fuel cell.

A fuel cell stack comprises: a substrate; a plurality of single fuel cells each of which includes a fuel side electrode, an electrolyte, and an oxygen side electrode deposited on the substrate; an interconnector film electrically connecting the fuel side electrode of one single fuel cell of adjacent single fuel cells of the plurality of single fuel cells and the oxygen side electrode of the other single fuel cell; and a porous ceramic film covering at least the interconnector film in a region between a first fuel side electrode of one single fuel cell of adjacent single fuel cells and a second fuel side electrode of the other single fuel cell.

A cell stack device includes a cell stack, a holding member, and a positive electrode terminal. The cell stack is constructed by stacking a plurality of cells. The holding member holds the cells. The positive electrode terminal functions as a positive electrode when power generated by the cell stack is output to the outside. The potential of the positive electrode terminal is not more than that of the holding member.

A fuel cell stack includes: a substrate; a first fuel cell including a fuel side electrode, an electrolyte, and an oxygen side electrode on the substrate, the first fuel cell being a single fuel cell; a second fuel cell including a fuel side electrode, an electrolyte, and an oxygen side electrode on the substrate, the second fuel cell being a single fuel cell; an interconnector film electrically connecting the fuel side electrode of the first fuel cell and the oxygen side electrode of the second fuel cell; and a porous ceramic film covering at least the interconnector film in a region between the fuel side electrode of the first fuel cell and the fuel side electrode of the second fuel cell.

A fuel cell stack includes: a substrate; a first fuel cell including a fuel side electrode, an electrolyte, and an oxygen side electrode on the substrate, the first fuel cell being a single fuel cell; a second fuel cell including a fuel side electrode, an electrolyte, and an oxygen side electrode on the substrate, the second fuel cell being a single fuel cell; an interconnector film electrically connecting the fuel side electrode of the first fuel cell and the oxygen side electrode of the second fuel cell; and a porous ceramic film covering at least the interconnector film in a region between the fuel side electrode of the first fuel cell and the fuel side electrode of the second fuel cell.

A single fuel cell according to the present disclosure includes a power generation section, a power non-generation section which does not include the power generation section, and an oxygen-ion-insulating gas seal film arranged so as to cover the surface of the power non-generation section, and the gas seal film is configured by a structure formed by firing a material containing MTiO.sub.3 (M: alkaline earth metal element) and metal oxide. The structure may include a first structure and a second structure which are different in composition, the first structure may include components derived from MTiO.sub.3 in larger amounts than the second structure, the second structure may include a metal element contained in the metal oxide in a larger amount than the first structure, and the area ratio of the second structure in the structure may be not less than 1% and not more than 50%.