Gas diffusion cathode using nanometer sized particles of transition metals for catalysis
A gas diffusion cathode for electrochemical cells provides higher power capability through the use of nano-particle catalysts. The catalysts comprise nanometer-sized particles of transition metals such as nickel, cobalt, manganese, iron, palladium, ruthenium, gold, silver, and lead, as well as alloys thereof, and respective oxides. These catalysts can substantially replace or eliminate platinum as a catalyst for oxygen reduction. Cathodes using such catalysts have applications to metal-air batteries, hydrogen fuel cells (PEMFCs), direct methanol fuel cells (DMFCs), direct oxidation fuel cells (DOFCs), and other air breathing electrochemical systems.
1 . A gas diffusion cathode, comprising a mixture of:
(a) carbon;
(b) a plurality of fluorocarbon particles; and
(c) a plurality of catalytic nano-particles selected from the group of transition metals of groups 8 , 1 b and 2 b of the periodic table, and/or an alloy of combinations thereof;
(d) wherein the mixture of the plurality of fluorocarbon particles, the carbon, and the plurality of catalytic nano-particles is compressed to form a physical structure for the cathode, the physical structure having first and second sides.
2 . The cathode of claim 1 , wherein the plurality of fluorocarbon particles comprises monomeric and/or polymeric compounds comprising both carbon and fluorine, the monomeric and/or polymeric compounds comprising a range of from 1% to 30% of the total weight of the mixture.
3 . The cathode of claim 2 , wherein the plurality of fluorocarbon particles comprises polytetrafluorethylene and/or poly(vinylidine fluoride).
4 . The cathode of claim 1 , wherein the carbon comprises a plurality of activated carbon particles having diameters ranging from roughly 5 nanometers to 1 micron.
5 . The cathode of claim 1 , wherein the carbon comprises a solid mass of porous carbon.
6 . The cathode of claim 1 , wherein the carbon comprises a sheet of porous carbon.
7 . The cathode of claim 1 , further comprising a current collector.
8 . The cathode of claim 1 , further comprising a hydrophobic layer bonded to the first side of the cathode.
9 . The cathode of claim 1 , wherein the catalytic nano-particles have diameters of less than 100 nanometers.
10 . The cathode of claim 9 , wherein the catalytic nano-particles have diameters of less than 30 nanometers.
11 . The cathode of claim 10 , wherein the catalytic nano-particles have diameters of less than 10 nanometers.
12 . The cathode of claim 11 , wherein the standard deviation of the nano-particle diameter distribution is less than four nanometers.
13 . The cathode of claim 11 , wherein the standard deviation of the nano-particle diameter distribution is less than two nanometers.
14 . The cathode of claim 1 , wherein a catalytic nano-particle comprises nickel and cobalt.
15 . The cathode of claim 1 , further comprising a base catalyst.
16 . The cathode of claim 15 , wherein the base catalyst comprises manganese.
17 . The cathode of claim 15 , wherein the base catalyst comprises platinum.
18 . The cathode of claim 15 , further comprising:
(a) a hydrophobic layer bonded to the first side of the cathode; and
(b) a current collector; wherein
(c) the base catalyst is manganese; and
(d) the catalytic nano-particles comprise nickel and cobalt; and
(e) the catalytic nano-particles have diameters that are less than 30 nanometers.
19 . A gas diffusion cathode, comprising a mixture of:
(a) a plurality of activated carbon particles,
(b) a plurality of fluorocarbon particles, and
(c) a plurality of catalytic nano-particles having diameters less than 10 nm, and compositions selected from the group of transition metals of groups 8 , 1 b and 2 b of the periodic table, or an alloy of combinations thereof;
(d) wherein the mixture of the plurality of fluorocarbon particles, the plurality of activated carbon particles, and the plurality of catalytic nano-particles is compressed to form a physical structure for the cathode that has first and second sides; and
(e) wherein the compressed structure is further laminated with a current collector structure through compression.