Nanoparticles and preparation method
The present invention concerns methods of forming metal-containing nanoparticles or oxide thereof, especially metal alloy nanoparticles. The method the steps of providing at least two different kinds of transition metal ion by providing at least two kinds of metal ion-containing compound; a heating step in which the at least two metal ion-containing compounds are subjected to a temperature of at least 300° C. to form the metal alloy nanoparticles; a cooling step comprising cooling the product of step b; and each metal ion-containing compound is a transition metal complex having ligands coordinated to a transition metal ion, the ligands being selected from the group consisting of glyoxime; a glyoxime derivative; salicylaldimine; and a salicylaldimine derivative. The preferred methods are solution-based methods. Products of the methods are also described, as are their uses as electrocatalysts, as well as uses of the metal ion-containing compounds for making nanoparticles.
1. A method of forming metal-containing nanoparticles or oxide thereof, the method comprising:
a. providing one or more transition metal ions by providing one or more metal ion-containing compounds;
b. dissolving the one or more metal ion-containing compounds in a solvent to form a solution phase comprising the one or more metal ion-containing compounds as a solute dissolved in the solvent, followed by drying the one or more metal ion-containing compounds that are dissolved in the solvent in order to recover a dried one or more metal ion-containing compounds;
c. a heating step in which the dried one or more metal ion-containing compounds are subjected to a temperature of at least 300° C. to form metal-containing nanoparticles or oxide thereof;
d. a cooling step comprising cooling the product of step c;
e. optionally, a passivating step in which the product of step d is passivated; and/or
f. optionally, a step of acid leaching the product of step d, or, if step e is performed, a step of acid leaching the product of step e;
wherein the one or more metal ion-containing compounds are transition metal complexes having ligands coordinated to a transition metal ion, the ligands being selected from the group consisting of glyoxime; a glyoxime derivative; salicylaldimine; and a salicylaldimine derivative.
2. The method according to claim 1 , wherein at least two transition metal ions are provided by at least two metal ion-containing compounds.
3. Metal-containing nanoparticles or oxide thereof, prepared by the method of claim 1 .
4. An electrocatalyst comprising the metal-containing nanoparticles or oxide thereof according to claim 3 .
5. An electrode comprising an electrocatalyst according to claim 4 .
6. A membrane electrode assembly comprising an electrode according to claim 5 .
7. A fuel cell comprising the membrane electrode assembly according to claim 6 .
8. The method according to claim 1 , wherein the ligands are glyoxime or a derivative thereof, preferably having the formula (HO)N=C(R1)-C(R2)=N(OH), wherein R1 and R2 are each independently H, hydroxy, alkoxy, carboxy or optionally substituted alkyl, aryl or heteroaryl group, or R1 and R2 join together to form a cyclic alkyl.
9. The method according to claim 1 , wherein step a further comprises providing a support such that the metal or metal alloy nanoparticles or oxide thereof are formed on the support.
10. The method according to claim 1 , wherein the metal ion-containing compound(s) comprise(s) one or more transition metal ions chosen from the group consisting of Pt, Pd, Fe, Ni, Co, Ir, Ru, Rh, Cu, Ag and Au.
11. The method according to claim 1 , wherein at least one of the metal ion-containing compounds comprises a transition metal ion which is Pt or Ni.
12. The method according to claim 1 , wherein the temperature of the heating step is between 600° C. and 1000° C.
13. The method according to claim 1 , wherein the heating step is carried out in an inert or reducing atmosphere or vacuum.
14. The method according to claim 1 , wherein the ligands are salicylaldimine or a derivative thereof, preferably having the formula (R3)N═CH-Ph-OH where Ph represents phenyl and the OH group is located ortho to the (R3)N═CH group, and R3 represents H, hydroxy, alkoxy, carboxy or optionally substituted alkyl, aryl or heteroaryl group.