Catalyst material for fuel cell
A method of forming a catalyst material includes coating agglomerates of catalyst support particles with an ionomer material. After coating the agglomerates of catalyst support particles, a catalyst metal precursor is deposited by chemical infiltration onto peripheral surfaces of the agglomerates of catalyst support particles. The catalyst metal precursor is then chemically reduced to form catalyst metal on the peripheral surfaces of the agglomerates of catalyst support particles.
1. A method of forming a catalyst material, the method comprising:
coating agglomerates of catalyst support particles with an ionomer material, the coating of the agglomerates of catalyst support particles including mixing the catalyst support particles, the ionomer material, and sodium bicarbonate and establishing a first predetermined pH level of the mixture;
after the coating of the agglomerates of catalyst support particles with the ionomer material, depositing by chemical infiltration a catalyst metal precursor onto peripheral surfaces of the agglomerates of catalyst support particles, the depositing including mixing the coated agglomerates of catalyst support particles with chloroplatinic acid and establishing a second predetermined pH level of the mixture such that a ratio of the first predetermined pH level to the second predetermined pH level is between 1.3 and 1.6; and
chemically reducing the catalyst metal precursor to form catalyst metal such that a majority of the catalyst metal resides on the peripheral surfaces of the agglomerates of catalyst support particles, the catalyst material comprising the ionomer material, the agglomerates of catalyst support particles and the catalyst metal.
2. The method as recited in claim 1 , wherein the first predetermined pH level is within a predetermined range of 8.5-9.0.
3. The method as recited in claim 1 , wherein the second predetermined pH level is within a predetermined range of 5.75-6.25.
4. The method as recited in claim 3 , further comprising bubbling carbon monoxide gas through the mixture including the coated agglomerates and the chloroplatinic acid.
5. The method as recited in claim 1 , wherein the chemically reducing includes using formaldehyde and establishing a pH level during the reducing to be 5.5-6.0.
6. The method as recited in claim 1 , further comprising, after the chemically reducing, drying the catalyst material and heating the catalyst material at a temperature that is greater than 150° C., 302° F.
7. The method as recited in claim 6 , further comprising washing the catalyst material in acid to remove sodium.