Ce_0.67Cr_0.33O_2.11: A New Low-Temperature O₂ Evolution Material and H₂ Generation Catalyst by Thermochemical Splitting of Water

Ce 0.67 Cr 0.33 O 2.11 was synthesized by hydrothermal method using diethylenetriamine as complexing agent ( Chem. Mater. 2008, 20, 7268). Ce 0.67 Cr 0.33 O 2.11 being the only compound likes UO 2+δ to have excess oxygen, it releases a large proportion of its lattice oxygen (0.167 M [O]/mole of compound) at relatively low temperature (465 °C) directly and it has been utilized for generation of H 2 by thermo-splitting of water. An almost stoichiometric amount of H 2 (0.152 M/Mole of compound) is generated at much lower temperature (65 °C). There is an almost comparable amount of oxygen release and hydrogen generation over this material at very low temperature compared to other CeO 2 −MO x (Mn, Fe, Cu, and Ni) mixed-oxide solid solutions (O 2 evolution ≥1300 °C and H 2 generation at 1000 °C). The reversible nature of oxygen release and intake of this material is attributed to its fluorite structure and coupling between the Ce 4+ /Ce 3+ and Cr 4+/6+ /Cr 3+ redox couples. Compound shows reversible oxygen release and intake by H 2 O absorption and subsequent hydrogen release to gain parent structure and hence this material can be utilized for generation of H 2 at very low temperature by thermo-chemical splitting of water.