Abstract: A fuel cell system including: an electrochemical pump including a first anode, a first cathode, and a first electrolyte membrane including a proton conductive oxide, the electrochemical pump separating hydrogen from a gas containing the hydrogen, and a solid oxide fuel cell that includes a second anode, a second cathode, and a second electrolyte membrane including a solid oxide electrolyte, and that generates electricity by reacting a fuel gas and an oxidant gas with each other.

Abstract: An electrode material of the present disclosure is an electrode material that includes a compound represented by the chemical formula BaZr1-x-yMxCoyO3-?. M is In or Yb, and the chemical formula satisfies 0<x<1, 0<y<1, 0<(x+y)<1, and 0<?<1. A membrane electrode assembly of the present disclosure includes a first electrode including the electrode material, and an electrolyte membrane provided on a first main surface of the first electrode.

Abstract: A proton conductor of the present disclosure includes a compound represented by the chemical formula BaZr(1-x-y)YbxScyO3-?. The chemical formula satisfies 0<x<0.5, 0 <y<0.5, (x+y)<0.5, and 0<?<0.5.

Abstract: The electrolyte membrane of the present disclosure includes a plurality of crystal domains. At least one of the crystal domains includes a first crystal subdomain and a second crystal subdomain. Each of the first crystal subdomain and the second crystal subdomain includes Ba, Zr, M, and O. M is a trivalent element. The concentration of M in the first crystal subdomain is different from the concentration of M in the second crystal subdomain.

Abstract: The electrochemical apparatus of the present disclosure includes a first stack that includes an oxide ion conductor as an electrolyte and decomposes water vapor to generate hydrogen and oxygen, a second stack that includes a proton conductor as an electrolyte and separates the hydrogen generated in the first stack from a gas mixture of the hydrogen and the water vapor that has not been decomposed in the first stack, and a heat insulation material that covers the first stack and the second stack.

Abstract: An electrochemical cell of the present disclosure includes a first cell and a second cell. The first cell includes a first electrolyte layer containing an oxide ion conductor. The second cell includes a second electrolyte layer containing a proton conductor, and the second cell is disposed to face the first cell.

Abstract: An electrochemical cell includes a first electrolyte layer containing an oxide-ion conductor, a second electrolyte layer containing a proton conductor, a first electrode which is disposed between the first electrolyte layer and the second electrolyte layer and in contact with a first principal surface of the first electrolyte layer and a first principal surface of the second electrolyte layer and into which a gas flows, a second electrode which is provided on a second principal surface of the first electrolyte layer and which generates oxygen, and a third electrode which is provided on a second principal surface of the second electrolyte layer and which generates hydrogen.

Abstract: A membrane electrode assembly according to the present disclosure is a membrane electrode assembly including: a solid electrolyte membrane containing an electrolyte material; and an electrode in contact with a reactant gas, wherein the electrode includes a structural support including a ceramic member, and a pore extending from a boundary surface in contact with the reactant gas toward the solid electrolyte membrane in the structural support and filled with a filler having at least one selected from the group consisting of hydrogen oxidation activity, oxygen reduction activity, proton reduction activity, steam decomposition activity, and oxide ion oxidation activity.

Abstract: A membrane electrode assembly of the present disclosure includes: an electrode including a composite material containing a metal and a proton-conducting first electrolyte; and an electrolyte layer including a proton-conducting second electrolyte, where the electrode and the electrolyte layer are stacked, and a volume ratio of the metal in the electrode is 57% or more.