Compositions, methods of making compositions, and hydrogen production via thermo-chemical splitting

Abstract

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.