Method for low temperature preparation of a noble metal alloy

Abstract

A method for producing fine, essentially contamination free, noble metal alloys is disclosed. The alloys comprise particles in a size range of 5 to 500 nm. The method comprises 1. A method for preparing a noble metal alloy at low temperature, the method comprising the steps of forming solution of organometallic compounds by dissolving the compounds into a quantity of a compatible solvent medium capable of solvating the organometallic, mixing a portion of each solution to provide a desired molarity ratio of ions in the mixed solution, rapidly quenching droplets of the mixed solution to initiate a solute-solvent phase separation as the solvent freezes, removing said liquid cryogen, collecting and freezing drying the frozen droplets to produce a dry powder, and finally reducing the powder to a metal by flowing dry hydrogen over the powder while warming the powder to a temperature of about 150° C.

What is claimed is:  
     
         1 . A method for preparing a noble metal alloy at low temperature, the method comprising the steps of: 
 (a) dissolving a first pure organometallic compound into a first quantity of a solvent medium, said compound comprising an organic ligand and one or more of a first transition noble metal ion, said solvent medium capable of solvating the organometallic ligand thereby providing a first dilute solution of said compound;    (b) dissolving a second pure organometallic compound into a second quantity of the solvent medium providing thereby a second dilute solution, said second organometallic compound comprising the organic ligand and one or more of a second transition noble metal ion;    (c) mixing a portion of said first dilute solution with a portion of said second dilute solution, said portions chose to provide a desired molarity ratio of ions in solution, said ratio equal to a desired alloy composition ratio;    (d) forming a plurality of droplets of said solution of step (c) and depositing said droplets into a quantity of a liquid cryogen thereby supercooling said droplets and initiating a solute-solvent phase separation into liquid solvent and solid crystallite, said supercooled liquid solvent rapidly freezing in said liquid cryogen;    (e) removing said liquid cryogen from said frozen droplets;    (f) collecting and handling the frozen droplets such that said droplets do not thaw or melt;    (g) removing the frozen solvent by sublimation at a reduced temperature and a reduced pressure, said step of removing resulting in a dry powder;    (h) flowing a reducing gas at an ambient pressure of about 1 atmosphere over said dry powder while warming said powder to a ambient temperature of below about 150° C.; and    (i) recovering said dry noble metal alloy powder.    
     
     
         2 . The method of  claim 1 , wherein said first and second dilute solutions further comprises a solute molarity concentration of about between 0.01 M to 0.2 M.  
     
     
         3 . The method of  claim 1 , wherein the solvent medium is 1,2 dichloroethane, or 1,2 dichlorotetrafluoroethane.  
     
     
         4 . The method of  claim 1 , wherein the liquid cryogen consists essentially of liquid nitrogen, liquid argon or liquid helium.  
     
     
         5 . The method of  claim 1 , wherein in transition noble metal ions are ions of metal selected from the list consisting of platinum, palladium, rhodium, ruthenium and rhenium.  
     
     
         6 . The method of  claim 1 , wherein the reducing gas is hydrogen or a mixture of hydrogen and argon.  
     
     
         7 . The method of  claim 1 , wherein the organic ligand is an acetoacetonate.  
     
     
         8 . The method of  claim 1 , wherein the organic ligand is a cyclooctadiene chloride or an acetate.  
     
     
         9 . A method for preparing a pure, noble metal powder at low temperatures, the method comprising the steps of: 
 (a) dissolving a pure organometallic compound into a quantity of a solvent medium, said compound comprising an organic ligand and one or more of a first transition noble metal ions, said solvent medium capable of solvating the organometallic ligand thereby providing a dilute solution of said compound;    (b) forming a plurality of droplets of said solution and depositing said droplets into a quantity of a liquid cryogen thereby supercooling said droplets and initiating a solute-solvent phase separation into liquid solvent and solid crystallites, said supercooled liquid solvent rapidly freezing in said liquid cryogen;    (c) removing said liquid cryogen from said frozen droplets;    (d) collecting and handling the frozen droplets such that said droplets do not thaw or melt;    (e) removing the frozen solvent by sublimation at a reduced temperature and a reduced pressure, said step of removing resulting in a dry powder;    (f) flowing a reducing gas at an ambient pressure of about 1 atmosphere over said dry powder while warming said powder to a ambient temperature of below about 150° C.; and    (g) recovering said dry noble metal powder.    
     
     
         10 . The method of  claim 9 , wherein said dilute solutions further comprises a solute molarity concentration of about between 0.01 M to 0.2 M.  
     
     
         11 . The method of  claim 9 , wherein the solvent medium is dioxane, 1,2 dichloroethane, or 1,2 dichlorotetrafluoroethane.  
     
     
         12 . The method of  claim 9 , wherein the liquid cryogen consists essentially of liquid nitrogen, liquid argon or liquid helium.  
     
     
         13 . The method of  claim 9 , wherein in transition noble metal ions are ions of metal selected from the list consisting of platinum, palladium, rhodium, ruthenium and rhenium.  
     
     
         14 . The method of  claim 9 , wherein the organic ligand is an acetoacetonate-based molecule.  
     
     
         15 . The method of  claim 9 , wherein the reducing gas is hydrogen or a mixture of hydrogen and argon.  
     
     
         16 . The method of  claim 9 , wherein the organic ligand is a cyclooctadiene-based or an acetate-based molecule.  
     
     
         17 . A catalyst comprising: 
 a) a solution comprising one or more pure organometallic compounds further comprising one or more precious metal ligands, said compounds dissolved in a solvent medium, said solvent capable of solvating the organometallic ligands thereby providing a solution of said compounds; and    b) an inert catalyst support, said support dispersed uniformly throughout said solution as a solution suspension, said solution suspension dispersed into a plurality of droplets, said droplets rapidly cooled so as to quickly freeze said suspension solution and thereby initiate a precipitation of said organometallic compounds onto said support forming thereby a dispersed support, said dispersed support freeze-dried to provide a coated support, said coated support exposed to a reducing gas while heated to a temperature of about below 150° C. to reduce said organic compounds and thereby providing a plurality of finely-divided noble metal alloy particles on said support, said particles and said support comprising said catalyst.    
     
     
         18 . The catalyst of  claim 17 , wherein said dilute solutions further comprises a solute molarity concentration of about between 0.01 M to 0.2 M.  
     
     
         19 . The catalyst of  claim 17 , wherein the solvent medium is dioxane, 1,2 dichloroethane, or 1,2 dichlorotetrafluoroethane.  
     
     
         20 . The catalyst of  claim 17 , wherein the reducing gas is hydrogen or hydrogen and an inert gas.  
     
     
         21 . The catalyst of  claim 17 , wherein said alloy particles have a major dimension size between about 5 nm and 500 nm.  
     
     
         22 . A low temperature method for preparing a noble metal alloy catalyst, the method comprising the steps of: 
 (a) dissolving a first pure organometallic compound into a first quantity of a solvent medium, said compound comprising an organic ligand and one or more of a first transition noble metal ion, said solvent medium capable of solvating the organometallic ligand thereby providing a first dilute solution of said compound;    (b) dissolving a second pure organometallic compound into a second quantity of the solvent medium providing thereby a second dilute solution, said second organometallic compound comprising the organic ligand and one or more of a second transition noble metal ion;    (c) mixing a portion of said first dilute solution with a portion of said second dilute solution, said portions chose to provide a desired molarity ratio of ions in solution, said ratio equal to a desired alloy composition ratio;    (d) an inert catalyst support, said support dispersed uniformly throughout said solution as a solution suspension, said solution suspension dispersed into a plurality of droplets, said droplets rapidly cooled so as to quickly freeze said suspension solution and thereby initiate a precipitation of said organometallic compounds onto said support forming thereby a dispersed support;    (e) removing the solvent by sublimation or evaporation, said step of removing resulting in dry crystallites deposited upon said porous support material; and    (f) flowing a reducing gas at an ambient pressure of about 1 atmosphere over said dispersed crystallites while heating said porous support material to a ambient temperature of below about 150° C. thereby reducing said dispersed crystallites to provide a plurality of finely-divided noble metal alloy particles on said support material, said particles and said support material comprising said catalyst.    
     
     
         23 . The method of  claim 22 , wherein the dilute solution of step of dissolving have a solute normality concentration of about between 0.01 M to 0.2 M.  
     
     
         24 . The method of  claim 22 , wherein the liquid cryogen consists essentially of liquid nitrogen, liquid argon or liquid helium.  
     
     
         25 . The method of  claim 22 , wherein in transition noble metal ions are ions of metal selected from the list consisting of platinum, palladium, rhodium, ruthenium and rhenium.  
     
     
         26 . The method of  claim 22 , wherein the organic ligand is an acetoacetonatebased molecule.  
     
     
         27 . The method of  claim 22 , wherein the reducing gas can be hydrogen or a mixture of hydrogen and argon.  
     
     
         28 . The method of  claim 22 , wherein the organic ligand is a cyclooctadiene-based or an acetate-based molecule.  
     
     
         29 . The catalyst of  claim 22 , wherein said alloy particles have a major dimension size between about 5 nm and 500 nm.  
     
     
         30 . A low temperature method for preparing an electrode having a noble metal alloy dispersed throughout, the method comprising the steps of: 
 (a) dissolving a first pure organometallic compound into a first quantity of a solvent medium, said compound comprising an organic ligand and one or more of a first transition noble metal ion, said solvent medium capable of solvating the organometallic ligand thereby providing a first dilute solution of said compound;    (b) dissolving a second pure organometallic compound into a second quantity of the solvent medium providing thereby a second dilute solution, said second organometallic compound comprising the organic ligand and one or more of a second transition noble metal ion;    (c) mixing a portion of said first dilute solution with a portion of said second dilute solution, said portions chose to provide a desired molarity ratio of ions in solution, said ratio equal to a desired alloy composition ratio;    (d) uniformly dispersing said solution onto a porous support material;    (e) removing the solvent by sublimation or evaporation, said step of removing resulting in a dry crystallites deposited upon said porous support material; and    (f) flowing a gas containing hydrogen gas at an ambient pressure of about 1 atmosphere over said dispersed, dry crystallites while heating said porous support material to a ambient temperature of below about 150° C. thereby reducing said dispersed crystallites to provide a plurality of finely-divided noble metal alloy particles on said porous support material, said particles and said porous support material comprising said electrode.    
     
     
         31 . The method of  claim 30 , wherein said first and second dilute solutions further comprises a solute molarity concentration of about between 0.01 M to 0.2 M.  
     
     
         32 . The method of  claim 30 , wherein the solvent medium is 1,2 dichloroethane or 1,2 dichlorotetrafluoroethane.  
     
     
         33 . The method of  claim 30 , wherein the liquid cryogen consists essentially of liquid nitrogen, liquid argon or liquid helium.  
     
     
         34 . The method of  claim 30 , wherein in transition noble metal ions are ions of metal selected from the list consisting of platinum, palladium, rhodium, ruthenium and rhenium.  
     
     
         35 . The method of  claim 30 , wherein the organic ligand is an acetoacetonatebased molecule.  
     
     
         36 . The method of  claim 30 , wherein the reducing gas is hydrogen or a mixture of hydrogen and argon.  
     
     
         37 . The method of  claim 30 , wherein the organic ligand is a cyclooctadiene-based or an acetate-based molecule.  
     
     
         38 . The catalyst of  claim 30 , wherein said alloy particles have a major dimension size between about 5 nm and 500 nm.  
     
     
         39 . A finely separated noble metal alloy, consisting essentially of: 
 an alloy having the composition M x N 1−x , wherein M and N are any of platinum, palladium, ruthenium, iridium, rhodium or rhenium and wherein M is not N, and wherein further x may vary between 0.01 and 0.99;    said alloy further comprising particles having a major dimension size between about 5 nm and 500 nm.    
     
     
         40 . An metal ink, comprising: 
 a liquid suspension system and noble metal particles having a major dimension size between about 5 nm and 500 nm, said particles consisting essentially of platinum, palladium, ruthenium, iridium, rhodium and rhenium or binary alloys thereof.