Carbon-titanium oxide electrocatalyst supports for oxygen reduction in PEM fuel cells
View Patent ↗A high surface area support material is formed of an intimate mixture of carbon clusters and titanium oxide clusters. A catalytic metal, such as platinum, is deposited on the support particles and the catalyzed material used as an electrocatalyst in an electrochemical cell such as a PEM fuel cell. The composite material is prepared by thermal decomposition and oxidation of an intimate mixture of a precursor carbon polymer, a titanium alkoxide and a surfactant that serves as a molecular template for the mixed precursors.
1. A method comprising:
forming a dispersion of a carbonizable polymer, a surfactant, and titanium alkoxide in a liquid medium;
evaporating the liquid medium to leave a material characterized by inter-dispersed clusters of carbon based polymer, surfactant, and titanium oxide;
heating the material to progressively decompose and volatilize the surfactant and alkoxide residue;
further heating the material to carbonize the carbonizable polymer, and to yield a porous composite, processing the composite to produce a carbon-titanium oxide substrate material, the proportions of carbonizable polymer and titanium alkoxide being determined to provide a desired carbon to titanium ratio in the carbon-titanium oxide substrate material and depositing platinum on the substrate material, wherein the carbon-titanium oxide substrate material comprises at least on of TiO x C 0.65 , TiO x C 1.3 or TiO x C 2.6 .
2. A method as recited in claim 1 in which the carbonizable polymer is a phenol-formaldehyde polymer.
3. A method as recited in claim 1 in which the liquid medium comprises water and an alcohol.
4. A method as recited in claim 1 in which the surfactant is a block copolymer comprising polypropylene oxide central blocks and polyethylene oxide end blocks.
5. A method as recited in claim 1 in which the surfactant is a block copolymer comprising polypropylene oxide central blocks and polyethylene oxide end blocks and the liquid medium comprises water and an alcohol.
6. A method as set forth in claim 1 wherein the depositing platinum comprises using diamine platinum (II) nitrite as a platinum source and hydrazine as a reducing agent.
7. A method as set forth in claim 1 wherein the depositing platinum comprises using hexachloroplatinic acid as a platinum source and ethylene glycol as a reducing agent solvent dispersant.
8. A method as set forth in claim 1 further comprising forming an electrode for the reduction of oxygen from the carbon-titanium oxide substrate material having platinum deposited thereon.
9. A method as set forth in claim 8 further comprising a polymer electrolyte membrane, and deposing the electrode on the membrane.
10. A method as set forth in claim 1 wherein the carbon-titanium oxide substrate material consists essentially of at least one of TiO x C 0.65 , TiO x C 1.3 or TiO x C 2.6 .
11. A method as set forth in claim 1 , wherein said porous composite has a BET surface area of 300-700 m 2 /g.
12. A method comprising:
forming a dispersion of a carbonizable polymer, a surfactant, and titanium alkoxide in a liquid medium;
evaporating the liquid medium to leave a material characterized by inter-dispersed clusters of carbon based polymer, surfactant, and titanium oxide;
heating the material to progressively decompose and volatilize the surfactant and alkoxide residue;
further heating the material to carbonize the carbonizable polymer, and to yield a porous composite of inter-dispersed carbon and titanium oxide, the proportions of carbonizable polymer and titanium alkoxide being determined to provide a desired carbon to titanium ratio in the porous composite, crushing the composite to particles of catalyst support material having a BET surface area of 300-700 m 2 /g and the particles comprising at least one of-TiO x C 0.65 , TiO x C 1.3 or TiO x C 2.6 .
13. A method as set forth in claim 12 wherein the carbon-titanium oxide substrate material consists essentially of at least one of TiO x C 0.65 , TiO x C 1.3 or TiO x C 2.6 .