Patent ID: 8859161

Claim:
A fuel cell comprising the proton-conductive inorganic thin film comprising an inorganic proton conductor represented by Formula 1 below: M 1 1-a M 2 a P x O y , Formula 1 wherein M 1 is a tetravalent metallic element, M 2 is at least one metallic element selected from the group consisting of a monovalent metallic element, a divalent metallic element, and a trivalent metallic element, 0≦a<1, x is a number from 1.5 to 3.5; and y is a number from 5 to 13, characterized in that conductive inorganic thin film is in an amorphous phase wherein a main peak at a Bragg angle of 2θ indicating a crystalline phase of SnP 2 O 7 is not present for a CuK-α X-ray wavelength of 1.541 Å.