Synthesis of nano crystalline niobia/carbon composites with improved hydrothermal stability
Novel transition element-embedded carbon materials and methods for forming the same. The embedded transition elements can be oxides or hydroxides and may include a transition metal. In some cases the transition element-embedded materials are catalytic material suitable for use in a variety of catalytic systems. According to one specific example, the transition element that is embedded is a niobia species.
1. A method for preparing a transition element carbon composite material comprising:
mixing a compound comprising a transition element with a precipitating agent in a sugar-containing solution at a high enough temperature and for a long enough time that the transition element precipitates to yield a hydroxide and/or oxide while the sugar simultaneously undergoes hydrothermal carbonization; and
heat treating the mixture to form a particulate transition element/carbon material having embedded transition element hydroxide and/or oxide species highly and evenly dispersed through the carbon particles.
2. The method of claim 1 wherein the transition element is a transition metal.
3. The method of claim 2 wherein the transition metal is selected from the group consisting of Ag, Au, Ce, Co, Cr, Cu, Fe, Ir, Mn, Mo, Ni, Pt, Ru, Ta, Ti, V, W, and Zr.
4. The method of claim 2 wherein the transition metal is niobium.
5. The method of claim 1 wherein the base precipitating agent is urea.
6. The method of claim 1 wherein the sugar solution is a glucose solution.
7. The method of claim 1 wherein the high enough temperature is at least 160° C.
8. The method of claim 7 wherein the high enough temperature is less than 240° C.
9. The method of claim 1 wherein the long enough time is at least 2 hours.
10. The method of claim 9 wherein the long enough time is less than 12 hours.
11. The method of claim 1 wherein the step of heat treatment comprises pyrolysis.
12. The method of claim 11 wherein pyrolization takes place in an inert atmosphere.
13. The method of claim 12 wherein pyrolization takes place in a N 2 rich atmosphere.
14. The method of claim 1 wherein the embedded transition element hydroxide and/or oxide species are in the form of discrete transition element hydroxide and/or oxide particles.
15. The method of claim 14 wherein the discrete transition element hydroxide and/or oxide particles comprise niobium.