摘要 |
According to one embodiment, the noble metal catalyst layer includes first noble metal layer and a second noble metal layer formed on the first noble metal layer. The first noble metal layer includes a first noble metal element and has a porosity of 65 to 95 vol. %, a volume of pores having a diameter of 5 to 80 nm accounts for 50% or more of a volume of total pores in the first noble metal layer. The second noble metal layer includes a second noble metal element, and has an average thickness of 3 to 20 nm and a porosity of 50 vol. % or less. |