Catalyst and electrode catalyst layer, membrane electrode assembly, and fuel cell using the catalyst
The present invention has an object to provide a catalyst having excellent oxygen reduction reaction activity. The present invention relates to a catalyst comprising a catalyst support and a catalyst metal supported on the catalyst support, wherein a specific surface area of the catalyst per support weight is 715 m 2 /g support or more or a covering ratio of the catalyst metal with an electrolyte is less than 0.5, and an amount of an acidic group of the catalyst per support weight is 0.75 mmol/g support or less.
1. A cathode catalyst layer for a fuel cell, comprising:
a cathode catalyst comprising a catalyst support and catalyst metal supported on the catalyst support,
wherein catalyst metal is supported inside mesopores having a radius of 1 nm or more of the catalyst support,
wherein a specific surface area of the cathode catalyst per support weight is 1200 m 2 /g support or more, and
wherein an amount of an acidic group of the cathode catalyst per support weight is 0.75 mmol/g support or less, and
an electrolyte,
wherein catalyst metal, which is present inside the mesopores, is not covered with the electrolyte.
2. The cathode catalyst layer according to claim 1 , further comprising:
catalyst metal covered with the electrolyte,
wherein a covering ratio of the catalyst metal covered with the electrolyte is less than 0.5.
3. The cathode catalyst layer according to claim 2 , wherein the covering ratio of the catalyst metal covered with the electrolyte is 0.4 or less.
4. The cathode catalyst layer according to claim 1 , wherein the support includes a metal oxide or carbon.
5. The cathode catalyst layer according to claim 1 , wherein the acidic group is at least one selected from the group consisting of a hydroxyl group, a lactone group, and a carboxyl group.
6. The cathode catalyst layer according to claim 1 , wherein the catalyst metal is platinum or includes platinum and a metal component other than platinum.
7. The cathode catalyst layer according to claim 1 , wherein an amount of the catalyst metal supported on the support is 50 wt % or less.
8. The cathode catalyst layer for the fuel cell set forth in claim 1 , wherein the amount of the acidic group of the cathode catalyst per support weight is 0.1 mmol/g support or more.
9. The cathode catalyst layer for the fuel cell set forth in claim 1 , wherein the specific surface area of the cathode catalyst per support weight is 1700 m 2 /g support or more.
10. A membrane electrode assembly for a fuel cell comprising the cathode catalyst layer for the fuel cell set forth in claim 1 .
11. A fuel cell comprising the membrane electrode assembly for the fuel cell set forth in claim 10 .
12. The fuel cell set forth in claim 11 , wherein the fuel cell is a polymer electrolyte fuel cell.
13. A method of manufacturing the cathode catalyst layer set forth in claim 1 , comprising:
supporting the catalyst metal on the catalyst support to obtain a catalyst powder; and
subjecting the catalyst powder to heat-treatment in a hydrogen atmosphere,
wherein the heat-treatment is carried out at a range of 900° C. to 1400° C. in temperature.
14. A cathode, comprising:
a cathode catalyst comprising a catalyst support and catalyst metal supported on the catalyst support,
wherein catalyst metal is supported inside mesopores having a radius of 1 nm or more of the catalyst support,
wherein a specific surface area of the cathode catalyst per support weight is 1700 m 2 /g support or more,
wherein an amount of an acidic group of the cathode catalyst per support weight is 0.75 mmol/g support or less, and
wherein catalyst metal, which is present inside the mesopores, is not covered with the electrolyte.