Nanoparticle deposition in porous and on planar substrates
A method of preparing a metal nanoparticle on a surface includes subjecting a metal source to a temperature and a pressure in a carrier gas selected to provide a vapor metal species at a vapor pressure in the range of about 10 −4 to about 10 −11 atm; contacting the vapor metal species with a heated substrate; and depositing the metal as a nanoparticle on the substrate.
1. A method of preparing a metal nanoparticle in or on a surface comprising:
subjecting a metal to a temperature and a pressure in a carrier gas selected to provide a vapor metal species at a vapor partial pressure in the range of about 10 −4 to about 10 −11 atm, wherein the vapor metal species comprises one or more of vaporized metal, metal oxyhydroxides and metal hydroxides;
transporting the vapor metal species in the carrier gas to a heated substrate, wherein the heated substrate is at a temperature that is lower than the temperature to which the metal is subjected; and
depositing the metal as a nanoparticle on the heated substrate.
2. The method of claim 1 , wherein the vapor metal species are deposited thermally as a nanoparticle.
3. The method of claim 2 , wherein thermally depositing comprises heating the metal at a first higher temperature and maintaining the heated substrate at a second lower temperature, wherein the vapor metal species decompose on contacting the heated substrate to deposit the metal nanoparticles.
4. The method of claim 1 , wherein the vapor metal species are deposited electrolytically as a nanoparticle.
5. The method of claim 4 , wherein electrolytically depositing comprises applying a voltage at the heated substrate to reduce the vapor metal species to metal.
6. The method of claim 1 , wherein the substrate is porous.
7. The method of claim 1 , wherein the carrier gas comprises water vapor.
8. The method of claim 1 , wherein the substrate is a porous anode of a solid oxide fuel cell.
9. The method of claim 1 , wherein the substrate is a solid support of a heterogeneous catalyst.
10. A method of depositing metal nanoparticles in a porous electrode of a solid oxide fuel cell, comprising:
heating a metal to a first temperature selected to vaporize the metal;
flowing a carrier gas over the heated metal, wherein the carrier gas interacts with the vaporized metal and forms a metallic species gas phase having a vapor pressure in the range of about 10 −4 to about 10 −11 atm, wherein the metallic species gas phase comprises one or more of vaporized metal, metal oxyhydroxides and metal hydroxides;
directing the metallic species gas phase towards a surface of a solid oxide fuel cell, wherein the surface comprises a porous electrode of the solid oxide fuel cell, and wherein the solid oxide fuel cell is independently heated to a second temperature that is less than the first temperature; and
decomposing the metallic species gas phase to deposit nanoparticles of the metal.
11. The method of claim 10 , wherein the electrode is an anode.
12. The method of claim 11 , wherein the anode further comprises an electronic oxide or mixed electronic ionic conductor (MIEC).
13. The method of claim 11 , wherein the deposited metal nanoparticles have a particle density in the range of 10 to 100 per μm 2 , and/or the deposited metal nanoparticles have a particle volume is in the range of 0.1 to 10 nm 3 /nm 2 .
14. The method of claim 10 , wherein the nanoparticles deposit at a triple phase boundary of the porous electrode.
15. The method of claim 14 , wherein the triple phase boundary is in the range of 5-100 μm/μm 3 .
16. The method of claim 11 , further comprising:
prior to deposition, heating the solid oxide fuel cell under reducing conditions, wherein nickel oxide present in the anode is reduced to nickel.
17. The method of claim 16 , wherein the nanoparticles deposit within pores of the porous substrate.
18. The method of claim 16 , wherein the carrier gas comprises water vapor.
19. The method of claim 16 , wherein the metal nanoparticles deposit in an anode active layer (AAL).