Compositions of nanometal particles containing a metal or alloy and platinum particles for use in fuel cells
A composition of nanoparticles of metal or an alloy or having a metal and alloy core with an oxide shell in admixture with platinum particles is useful as a component for electrodes. More particularly, such composition is useful as an electrode ink for the reduction of oxygen as well as the oxidation of hydrocarbon or hydrogen fuel in a direct oxidation fuel cell, such as, but not limited to, the direct methanol fuel cell. These electrodes encompass a catalyst ink containing platinum, the nanoparticles, and a conducting ionomer which may be directly applied to a conductive support, such as woven carbon paper or cloth. This electrode may be directly adhered onto an ion exchange membrane. The nanoparticles comprise nanometer-sized transition metals such as cobalt, iron, nickel, ruthenium, chromium, palladium, silver, gold, and copper. In this invention, these catalytic powders substantially replace platinum as a catalyst in fuel cell electrooxidation and electroreduction reactions.
1 . A composition comprising
a) nanoparticles of at least one metal;
b) nanoparticles of an alloy of two or more metals;
c) nanoparticles having a core of the at least one metal and an oxide shell;
d) nanoparticles having a core of the alloy and an oxide shell; or
e) mixtures thereof;
in admixture with platimun particles.
2 . The composition of claim 1 , wherein the platinum particles are finely divided platinum particles.
3 . The composition of claim 2 , wherein the platinum particles have a diameter of less than 100 nm.
4 . The composition of claim 1 , wherein the nanoparticles have a diameter of less than 50 nm.
5 . The composition of claim 4 , wherein the nanoparticles have a diameter of less than 30 nm.
6 . The composition of claim 5 , wherein the nanoparticles have a diameter of less than 15 nm.
7 . The composition of claim 1 , wherein the metal or metals are selected from the group consisting of cobalt, iron, nickel, ruthenium, chromium, palladium, silver, gold, and copper.
8 . The composition of claim 1 , comprising wherein the nanoparticles comprise the alloy.
9 . The composition of claim 8 , wherein a first metal in the alloy is greater than 5% by weight of the alloy.
10 . The composition of claim 9 , where the first metal in the alloy is greater than 10% by weight of the alloy.
11 . The composition of claim 10 , where the first metal in the alloy is greater than 25% by weight of the alloy.
12 . The composition of claim 11 , where the first metal in the alloy is greater than 50% by weight of the alloy.
13 . The composition of claim 12 , where the first metal in the alloy is greater than 90% by weight of the alloy.
14 . The composition of claim 1 , wherein the nanoparticles comprise one or two metals selected from the group consisting of cobalt, iron, nickel, ruthenium, chromium, palladium, silver, gold, and copper.
15 . The composition of claim 1 , further comprising an ionomer.
16 . The composition of claim 15 , wherein the ionomer is a proton-conducting ionomer.
17 . The composition of claim 15 , wherein the ionomer is less than 40% by weight of a combined weight of the nanoparticles and the platinum particles in the composition.
18 . The composition of claim 1 , wherein the nanoparticles are 5% or more by weight of a combined weight of the nanoparticles and the platinum particles in the composition.
19 . The composition of claim 18 , wherein the nanoparticles are 25% or more by weight of a combined weight of the nanoparticles and the platinum particles in the composition.
20 . The composition of claim 19 , wherein the nanoparticles are 50% or more by weight of a combined weight of the nanoparticles and the platinum particles in the composition.
21 . The composition of claim 20 , wherein the nanoparticles are 75% or more by weight of a combined weight of the nanoparticles and the platinum particles in the composition.
22 . The composition of claim 21 , wherein the nanoparticles are 90% or more by weight of a combined weight of the nanoparticles and the platinum particles in the composition.
23 . The composition of claim 15 , wherein the ionomer is a perfluorinated resin having both hydrophobic and hydrophilic properties.
24 . The composition of claim 23 , wherein the perfluorinated resin is a conducting polymer.
25 . An electrode comprising the composition of claim 15 , and an electron-conducting support.
26 . A method of producing an electrode comprising
applying the composition of claim 15 to an electron-conducting support.
27 . A fuel cell comprising the electrode of claim 25.