Tin oxide, electrode catalyst for fuel cells, membrane electrode assembly, and solid polymer fuel cell
Disclosed is a tin oxide containing antimony and at least one element A selected from the group consisting of tantalum, tungsten, niobium, and bismuth. The antimony and the at least one element A selected from the group consisting of tantalum, tungsten, niobium, and bismuth are preferably dissolved in a solid state in tin oxide. The ratio of the number of moles of the element A to the number of moles of antimony, i.e., [(the number of moles of the element A/the number of moles of antimony)], is preferably 0.1 to 10.
1. Tin oxide containing antimony and at least one element A selected from the group consisting of tantalum, tungsten, niobium, and bismuth;
said tin oxide being an electrode material of a fuel cell;
wherein a mole ratio of antimony to tin in said tin oxide is 0.01 to 0.05.
2. The tin oxide according to claim 1 , wherein the antimony and the at least one element A selected from the group consisting of tantalum, tungsten, niobium, and bismuth are dissolved in a solid state in tin oxide.
3. The tin oxide according to claim 1 , wherein the antimony and/or the at least one element A selected from the group consisting of tantalum, tungsten, niobium, and bismuth are present in tin oxide in the form of an oxide.
4. The tin oxide according to claim 1 , wherein the ratio of the number of moles of the element A to the number of moles of antimony is 0.1 to 10.
5. A fuel cell electrode catalyst comprising the tin oxide according to claim 1 having a catalyst supported thereon.
6. A membrane-electrode assembly comprising a polymer electrolyte membrane and a pair of electrodes, one being an oxygen electrode with the other being a fuel electrode, one on each side thereof, at least one of the oxygen electrode and the fuel electrode containing the fuel cell electrode catalyst according to claim 5 .
7. A polymer electrolyte fuel cell comprising the membrane-electrode assembly according to claim 6 and a separator on each side of the membrane-electrode assembly.
8. The tin oxide according to claim 2 , wherein the ratio of the number of moles of the element A to the number of moles of antimony is 0.1 to 10.
9. The tin oxide according to claim 3 , wherein the ratio of the number of moles of the element A to the number of moles of antimony is 0.1 to 10.
10. A fuel cell electrode catalyst comprising the tin oxide according to claim 2 having a catalyst supported thereon.
11. A fuel cell electrode catalyst comprising the tin oxide according to claim 3 having a catalyst supported thereon.