Segregation induced core-shell structure
A process for synthesis of PtNi high surface area core/shell particles. The processing including formation of PtNi nanoparticles, exposure of the PtNi nanoparticles to oxygen to form a nickel oxide coating on the nanoparticles at the same time the segregation of Ni to surface induces a Pt-skin with PtNi core structure, removal of the nickel oxide coating to form PtNi core/Pt shell (or Pt-skin) structure.
1. A method of synthesizing Pt shell PtNi core nanoparticle comprising the steps of:
forming a reaction mixture comprising a nickel precursor, a reducing agent, and a surfactant comprising one part oleic acid to two parts oleylamine, a platinum precursor, and a polar solvent;
reacting the reaction mixture at between 195° C. and 205° C. for at least 10 minutes forming a PtNi nanoparticle solution;
isolating PtNi nanoparticles from the PtNI nanoparticle solution;
exposing the PtNi nanoparticles to oxygen;
forming nickel oxide by reaction of nickel of the PtNi nanoparticles with the oxygen; and
removing the nickel oxide from at a portion of the PtNi nanoparticles.
2. The method of claim 1 , wherein isolation of the PtNi nanoparticles comprises:
sonicating the PtNi nanoparticle solution with substrate in chloroform solution;
adding hexane to the sonicated chloroform solution;
precipitating PtNi nanoparticles; and
collecting the PtNi nanoparticles by filtration.
3. The method of claim 1 , wherein exposing the PtNi nanoparticles comprises exposure at a temperature of 150° C. to 400° C.
4. The method of claim 3 , wherein exposing the PtNi nanoparticles comprises exposure at a temperature of 150° C. to 300° C.
5. The method of claim 3 , wherein the exposing the PtNi nanoparticles is for 1 to 20 hours.
6. The method of claim 1 , wherein removing the nickel oxide is by acid leaching.
7. The method of claim 6 , wherein the acid leaching is by exposure of an equal volume of acid to nanoparticle.
8. The method of claim 6 , wherein the acid leaching is by exposure to HClO 4 .
9. A method of synthesizing Pt shell PtNi core nanoparticle comprising the steps of:
forming a reaction mixture comprising a nickel precursor, a reducing agent, and a surfactant comprising one part oleic acid to two parts oleylamine, a platinum precursor, and a polar solvent;
reacting the reaction mixture at between 195° C. and 205° C. for at least 10 minutes forming a PtNi nanoparticle solution;
isolating PtNi nanoparticles from the PtNI nanoparticle solution;
exposing the PtNi nanoparticles to oxygen at a temperature of 150° C. to 400° C. for 1 to 20 hours;
forming nickel oxide on a surface of the PtNi nanoparticles by reaction of nickel of the PtNi nanoparticles with the oxygen; and
removing the nickel oxide from at a portion of the PtNi nanoparticles.
10. The method of claim 9 , wherein isolation of the PtNi nanoparticles comprises:
sonicating the PtNi nanoparticle solution with substrate in chloroform solution;
adding hexane to the sonicated chloroform solution;
precipitating PtNi nanoparticles; and
collecting the PtNi nanoparticles by filtration.
11. The method of claim 9 , wherein exposing the PtNi nanoparticles comprises exposure at a temperature of 150° C. to 300° C.
12. The method of claim 9 , wherein removing the nickel oxide is by acid leaching.
13. The method of claim 12 , wherein the acid leaching is by exposure of an equal volume of acid to nanoparticle.
14. The method of claim 12 , wherein the acid leaching is by exposure to HClO 4 .