Fuel cells incorporating silica fibers
Embodiments of the invention include fuel cells incorporating sheets and/or powders of silica fibers and methods for producing such devices. The silica fibers may be formed via electrospinning of a sol gel produced with a silicon alkoxide reagent, such as tetraethyl ortho silicate, alcohol solvent, and an acid catalyst.
1. A method of fabricating a fuel cell, the method comprising:
forming a first sheet of silica fibers at least in part by (i) producing a sol-gel from an initial sol containing 75% to 90% TEOS by weight, 8% to 25% ethanol by weight, an acid catalyst, and the balance water, and (ii) electrospinning the sol-gel;
forming an electrolyte layer at least in part by, after and/or during the electrospinning, incorporating a first functional material onto the silica fibers;
disposing a first catalyst layer on an anode side of the electrolyte layer, the first catalyst layer being configured to receive a hydrogen-containing fuel, oxidize hydrogen from the fuel, and supply protons to the electrolyte layer; and
disposing a second catalyst layer on a cathode side of the electrolyte layer, the second catalyst layer being configured to receive protons from the electrolyte layer, receive oxygen, and reduce the oxygen to form water to thereby enable the production of electrical current by the fuel cell.
2. The method of claim 1 , wherein at least one of the first catalyst layer or the second catalyst layer comprises a support layer incorporating a catalyst material.
3. The method of claim 2 , wherein the catalyst material comprises at least one of platinum, one or more platinum-group metals, nickel, ruthenium, palladium, cerium oxide, or an alloy of platinum with one or more other metals.
4. The method of claim 2 , wherein the support layer comprises a sheet of silica fibers.
5. The method of claim 2 , wherein the support layer comprises carbon or a carbon-containing material.
6. The method of claim 1 , wherein the first catalyst layer comprises a second sheet of silica fibers, the first catalyst layer being provided at least in part by electrospinning a second sol-gel.
7. The method of claim 6 , further comprising incorporating one or more catalyst materials, or precursors thereof, into the second sol-gel prior to electrospinning thereof, wherein the second sheet of silica fibers comprises the one or more catalyst materials incorporated therein and/or thereon.
8. The method of claim 1 , wherein the second catalyst layer comprises a third sheet of silica fibers, the second catalyst layer being provided at least in part by electrospinning a third sol-gel.
9. The method of claim 8 , further comprising incorporating one or more catalyst materials, or precursors thereof, into the third sol-gel prior to electrospinning thereof, wherein the third sheet of silica fibers comprises the one or more catalyst materials incorporated therein and/or thereon.
10. The method of claim 1 , further comprising:
disposing a first diffusion layer on the first catalyst layer opposite the electrolyte layer, the first diffusion layer being configured to transport the hydrogen-containing fuel to the first catalyst layer; and/or
disposing a second diffusion layer on the second catalyst layer opposite the electrolyte layer, the second diffusion layer being configured to transport oxygen to the second catalyst layer.
11. The method of claim 10 , wherein the first diffusion layer comprises a fourth sheet of silica fibers, the first diffusion layer being provided at least in part by electrospinning a fourth sol-gel; and/or
wherein the second diffusion layer comprises a fifth sheet of silica fibers, the second diffusion layer being provided at least in part by electrospinning a fifth sol-gel.
12. The method of claim 1 , wherein the first functional material comprises a fluoropolymer, potassium hydroxide, and/or phosphoric acid.
13. The method of claim 1 , wherein producing the sol-gel comprises ripening the initial sol for at least 2 days at a humidity of 40% to 80% and a temperature of 50° F. to 90° F.
14. The method of claim 13 , wherein the initial sol is ripened for at least 3 days.
15. The method of claim 13 , wherein the sol-gel is electrospun when the weight of the sol-gel ranges from 10% to 60% of a starting weight of the initial sol prior to ripening.
16. The method of claim 13 , wherein the sol-gel is electrospun when production of ethylene vapor therefrom ranges from 10% to 40% relative to the initial sol prior to ripening.
17. The method of claim 1 , wherein forming the electrolyte layer comprises disposing the first sheet of silica fibers adjacent to one or more non-silica membranes.
18. The method of claim 17 , wherein forming the electrolyte layer comprises disposing the first sheet of silica fibers between two non-silica membranes.
19. The method of claim 17 , wherein the one or more non-silica membranes comprise a polymeric material.