Metal-alloy graphene nanocomposites and methods for their preparation and use
View Patent ↗Methods of forming a metal-alloy graphene nanocomposites are provided. The methods include providing a graphene substrate and forming a conducting polymer layer on a first major surface of the graphene substrate. The methods also include pyrolyzing the conducting polymer layer to form a nitrogen-doped graphene substrate and dispersing a plurality of metal-alloy nanoparticles on a first surface of the nitrogen-doped graphene substrate to form the nanocomposite.
1. A method of forming a metal-alloy graphene nanocomposite, the method comprising:
providing a graphene substrate;
forming a conducting polymer layer on a first major surface of the graphene substrate;
pyrolyzing the conducting polymer layer to form a nitrogen-doped graphene substrate; and
dispersing a plurality of metal-alloy nanoparticles on a first surface of the nitrogen-doped graphene substrate to form the nanocomposite.
2. The method of claim 1 , wherein the conducting polymer layer comprises polypyrrole (PPy), polyaniline (PANI), polycarbazole, polyindole, polyazepine, or combinations thereof.
3. The method of claim 1 , wherein the plurality of metal-alloy nanoparticles comprises a combination of platinum (Pt) and an alloying transition metal.
4. The method of claim 3 , wherein the alloying transition metal is a 3d transition metal.
5. The method of claim 3 , wherein the alloying transition metal comprises cobalt (Co), iron (Fe), nickel (Ni), or combinations thereof.
6. The method of claim 1 , wherein forming the conducting polymer layer comprises:
functionalizing the graphene substrate with a negatively charged polyelectrolyte to form a functionalized graphene substrate; and
polymerizing the functionalized graphene substrate using a polymerizable heterocyclic aromatic compound to form a positively charged conducting polymer layer on the graphene substrate.
7. The method of claim 6 , wherein the negatively charged polyelectrolyte comprises poly(sodium 4-styrene sulfonate) (PSSS), sodium polyarylate, polyanetholesulfonic acid sodium salt, poly(2-acrylamido-2-methyl-1-propanesulfonic acid-co-acrylonitrile), poly(2-acrylamido-2-methyl-1-propanesulfonic acid) solution, poly(vinyl sulfate) potassium salt, poly(vinylsulfonic acid, sodium salt) solution, 4-styrenesulfonic acid sodium salt hydrate, poly(4-styrenesulfonic acid-co-maleic acid) sodium salt solution, or combinations thereof.
8. The method of claim 6 , wherein the polymerizable heterocyclic aromatic compound comprises pyrrole, aniline, carbazole, indole, azepine, or combinations thereof.
9. The method of claim 1 , wherein pyrolyzing the conducting polymer layer comprises heating the graphene substrate with the polymer layer in presence of an inert gas to form the nitrogen-doped graphene substrate.
10. The method of claim 1 , wherein the plurality of metal-alloy nanoparticles is dispersed on the nitrogen-doped graphene substrate by a polyol reduction technique in presence of a reducing agent.
11. A method of forming a metal-alloy graphene nanocomposite, the method comprising:
providing a graphene substrate;
functionalizing the graphene substrate with a negatively charged polyelectrolyte to form a functionalized graphene substrate;
polymerizing the functionalized graphene substrate using a polymerizable heterocyclic aromatic compound to form a positively charged conducting polymer layer on the graphene substrate; and
pyrolyzing the conducting polymer layer to form a nitrogen-doped graphene substrate.
12. The method of claim 11 , further comprising dispersing a plurality of metal-alloy nanoparticles on a first major surface of the nitrogen-doped graphene substrate to form the nanocomposite.
13. The method of claim 11 , wherein the conducting polymer layer comprises polypyrrole (PPy), polyaniline (PANI), polycarbazole, polyindole, polyazepine, or combinations thereof.
14. The method of claim 11 , wherein the negatively charged polyelectrolyte comprises poly(sodium 4-styrene sulfonate) (PSSS), sodium polyacrylate, polyanetholesulfonic acid sodium salt, poly(2-acrylamido-2-methyl-1-propanesulfonic acid-co-acrylonitrile), poly(2-acrylamido-2-methyl-1-propanesulfonic acid) solution, poly(vinyl sulfate) potassium salt, poly(vinylsulfonic acid, sodium salt) solution, 4-styrenesulfonic acid sodium salt hydrate, poly(4-styrenesulfonic acid-co-maleic acid) sodium salt solution, or combinations thereof.
15. The method of claim 11 , wherein the polymerizable heterocyclic aromatic compound comprises pyrrole, aniline, carbazole, indole, azepine, or combinations thereof.
16. The method of claim 11 , wherein pyrolyzing the conducting polymer layer comprises heating the graphene substrate with the polymer layer in presence of an inert gas to form the nitrogen-doped graphene substrate.
17. A metal-alloy graphene nanocomposite comprising:
a nitrogen-doped graphene substrate; and
a plurality of metal-alloy nanoparticles dispersed on a first major surface of the nitrogen doped graphene substrate,
wherein the nitrogen-doped graphene substrate is formed by coating a conducting polymer layer on a first major surface of a graphene substrate and pyrolyzing the conducting polymer layer to form the nitrogen-doped graphene substrate.
18. The metal-alloy graphene nanocomposite of claim 17 , wherein the conducting polymer layer comprises polypyrrole (PPy), polyaniline (PANI), polycarbazole, polyindole, polyazepine, or combinations thereof.
19. The metal-alloy graphene nanocomposite of claim 17 , wherein an atomic percentage of nitrogen in the nitrogen-doped graphene substrate is about 4% to about 8%.
20. The metal-alloy graphene nanocomposite of claim 19 , wherein the atomic percentage of nitrogen in the nitrogen-doped graphene substrate is about 6%.
21. The metal-alloy graphene nanocomposite of claim 17 , wherein the plurality of metal-alloy nanoparticles comprises a combination of platinum (Pt) and an alloying transition metal.
22. The metal-alloy graphene nanocomposite of claim 21 , wherein the alloying transition metal comprises cobalt (Co), iron (Fe), nickel (Ni), or combinations thereof.
23. The metal-alloy graphene nanocomposite of claim 21 , wherein the plurality of metal-alloy nanoparticles comprises platinum and cobalt having an atomic ratio of about 3:1.
24. The metal-alloy graphene nanocomposite of claim 17 , wherein the nanocomposite is configured as an electrocatalyst for use in a proton exchange membrane fuel cell (PEMFC).
25. An electrocatalyst, comprising:
a nitrogen-doped graphene substrate; and
a plurality of platinum-cobalt alloy nanoparticles dispersed on a first major surface of the nitrogen-doped graphene substrate,
wherein an atomic ratio of platinum and cobalt in the plurality of platinum-cobalt alloy nanoparticles is about 3:1.
26. The electrocatalyst of claim 25 , wherein the weight of the plurality of platinum-cobalt alloy nanoparticles is about 30% of the total weight of the electrocatalyst.
27. The electrocatalyst of claim 25 , wherein an average size of the platinum-cobalt alloy nanoparticles is about 2.2 nanometers to about 2.8 nanometers.
28. The electrocatalyst of claim 25 , wherein a current density of the electrocatalyst measured at a potential of about 0.5 Volts (V) is about 1560 mA cm −2 .
29. The electrocatalyst of claim 25 , wherein a power density of the electrocatalyst at a temperature of about 60° C. is about 805 mW cm −2 .
30. The electrocatalyst of claim 25 , wherein the electrocatalyst is configured as an electrode of a proton exchange membrane fuel cell (PEMFC).
31. An electrocatalyst formed by providing a nitrogen-doped graphene substrate and dispersing a plurality of platinum-cobalt alloy nanoparticles on a first surface of the nitrogen-doped graphene substrate, wherein providing the nitrogen-doped graphene substrate comprises forming a polypyrrole layer on a first major surface of a graphene substrate and subsequently pyrolyzing the polypyrrole layer to form the nitrogen-doped graphene substrate.
32. The electrocatalyst of claim 31 , wherein pyrolyzing the polypyrrole layer comprises heating the nitrogen-doped graphene substrate with the polypyrrole layer in presence of argon gas at a temperature of about 600° C. to about 800° C.
33. The electrocatalyst of claim 32 , wherein the nitrogen-doped graphene substrate with the polypyrrole layer is heated for about 1 hour to about 2 hours.
34. The electrocatalyst of claim 31 , wherein dispersing the plurality of platinum-cobalt alloy nanoparticles on the nitrogen-doped graphene substrate comprises dispersing the plurality of platinum-cobalt alloy nanoparticles by a microwave polyol reduction technique using ethylene glycol, chloroplatinic acid (H 2 PtCl 6 ) and cobalt nitrate (Co(NO 3 ) 2 ).
35. The electrocatalyst of claim 34 , wherein the plurality of platinum-cobalt alloy nanoparticles is dispersed on the nitrogen-doped graphene substrate within about 90 seconds.