Advanced electrocatalysts for oxygen reduction reaction
Provided are nanocomposites including an iron-based core and a nitrogen-doped graphitic carbon shell, and methods of making and using the same. Included in the nanocomposites is an Fe 3 C-based interlayer between the core and the shell. The nanocomposites can show a catalytic activity toward reducing oxygen comparable to commercial Pt/C catalysts.
1. A fuel cell comprising an Oxygen Reduction Reaction (ORR) catalyst comprising:
(a) a core comprising α-Fe and Fe 3 C; and
(b) a graphitic carbon shell that is nitrogen-doped;
wherein the ORR catalyst is substantially free of iron oxide, as characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), or both.
2. The fuel cell of claim 1 , wherein the ORR catalyst is a nanorod.
3. The fuel cell of claim 2 , wherein a diameter of the nanorod is from about 20 nm to about 30 nm, and wherein a length of the nanorod is from about 1 μm to about 2 μm.
4. The fuel cell of claim 1 , wherein the core comprises a crystalline structure.
5. The fuel cell of claim 1 , further comprising one or more X-ray diffraction peaks that correspond to a presence of α-Fe.
6. The fuel cell of claim 1 , further comprising one or more X-ray diffraction peaks that correspond to (002) planes of graphitic carbon.
7. The fuel cell of claim 1 , further comprising X-ray diffraction peaks that correspond to crystalline planes of Fe 3 C.
8. The fuel cell of claim 1 , the ORR catalyst comprising about 48.5% iron, about 45.2% carbon, and about 6.3% nitrogen.
9. The fuel cell of claim 1 , further comprising: one or more X-ray diffraction peaks that correspond to a presence of α-Fe;
one or more X-ray diffraction peaks that correspond to (002) planes of graphitic carbon; and
X-ray diffraction peaks that correspond to crystalline planes of Fe 3 C.
10. A fuel cell comprising an Oxygen Reduction Reaction (ORR) catalyst comprising:
(a) a core comprising α-Fe and Fe 3 C; and
(b) a graphitic carbon shell that is nitrogen-doped;
wherein the core comprises a catalytically effective amount of α-Fe.
11. A fuel cell comprising an Oxygen Reduction Reaction (ORR) catalyst comprising:
(a) a core consisting of α-Fe and Fe 3 C; and
(b) a graphitic carbon shell that is nitrogen-doped.
12. The fuel cell of claim 1 , further comprising an electrode comprising the ORR catalyst.
13. Use of the fuel cell of claim 1 to reduce oxygen.
14. A method of making a fuel cell of claim 1 , the method comprising:
(a) forming a Fe 3+ /cyanamide composite; and
(b) annealing the Fe 3 + /cyanamide composite.
15. The method of claim 14 , wherein forming the Fe 3+ /cyanamide composite comprises drying at a temperature of less than about 500° C.
16. The method of claim 14 , wherein annealing the Fe 3+ /cyanamide composite comprises polymerizing the cyanamide at a temperature of less than about 600° C.
17. The method of claim 14 , wherein annealing the Fe 3+ /cyanamide composite comprises heating the Fe 3+ /cyanamide composite to a temperature of about 750° C.
18. The method of claim 14 , wherein annealing the Fe 3+ /cyanamide composite comprises heating at a rate of about 4° C./min.
19. The method of claim 14 , wherein annealing the Fe 3+ /cyanamide composite comprises maintaining the temperature at about 750° C. for about 3 hours.
20. The method of claim 14 , wherein annealing the Fe 3+ /cyanamide composite comprises reducing Fe 3+ to Fe.