COMPOSITIONS, METHODS OF MAKING COMPOSITIONS, AND HYDROGEN PRODUCTION VIA THERMO-CHEMICAL SPLITTING
The present disclosure provides for compositions, methods of making compositions, and methods of using the composition. In an aspect, the composition can be a reactive material that can be used to split a gas such as water or carbon dioxide.
1 . A composition comprising: a crystalline compound having the formula X y Ce 1-y O 2 , wherein y is from 0.01 to 0.15, wherein X is Pr or Tb, wherein the crystalline compound has an average crystalline size of about 20 to 30 nanometers as determined by X-ray diffraction (XRD) data using the Scherrer equation prior to thermochemical water splitting and about 40 to 50 nanometers after 6 cycles of thermochemical water splitting.
2 . The composition of claim 1 , wherein X is Pr.
3 . The composition of claim 1 , wherein X is Tb.
4 . The composition of claim 1 , wherein y is 0.1.
5 . A method of making a crystalline compound having the formula X y Ce 1-y O 2 comprising:
mixing CeO 2 nanoparticles in water to form a CeO 2 dispersion, wherein the CeO 2 nanoparticles have an average size of about 15 to 30 nm;
mixing the CeO 2 dispersion with a nitrate of a rare earth element selected from praseodymium or terbium to form a second dispersion;
precipitating the rare earth element as a hydroxide onto the CeO 2 nanoparticles to form modified CeO 2 nanoparticles;
separating and drying the modified CeO 2 nanoparticles; and
heating the modified CeO 2 nanoparticles to decompose the hydroxides to form a rare earth element oxide and to form the crystalline compound having the formula X y Ce 1-y O 2 , wherein y is from 0.01 to 0.15, wherein X is Pr or Tb.
6 . The method of claim 5 , wherein precipitating includes adding sodium hydroxide to the second dispersion.
7 . The method of claim 5 , wherein heating includes heating at about 800-1000° C. for 2 to 6 hours.
8 . A method of splitting water, comprising:
exposing water to a crystalline compound, in a reduced form, in the presence of an inert gas, wherein the crystalline compound has the formula X y Ce 1-y O 2 , wherein y is from 0.01 to 0.15, wherein X is Pr or Tb;
oxidizing the crystalline compound with the water to produce H 2 , at a first temperature; and
regenerating the crystalline compound during the step of reducing at a second temperature, wherein O 2 is released during regeneration and after O 2 is released H 2 is released during regeneration,
wherein the first temperature is about 1000 to 1450° C., wherein the second temperature is about 1000 to 1450° C.
9 . The method of claim 8 , wherein the reducing and oxidizing steps are performed under substantially isothermal conditions, wherein the difference between the first temperature and the second temperature is less than 100° C.
10 . The method of claim 8 , wherein the crystalline compound has an average crystalline size of about 20 to 30 nanometers as determined by X-ray diffraction (XRD) data using the Scherrer equation prior to thermochemical water splitting and about 40 to 50 nanometers after six cycles of thermochemical water splitting.