Ce0.67Cr0.33O2.11: A New Low-Temperature O2 Evolution Material and H2 Generation Catalyst by Thermochemical Splitting of Water

Abstract

Ce0.67Cr0.33O2.11 was synthesized by hydrothermal method using diethylenetriamine as complexing agent (Chem. Mater. 2008, 20, 7268). Ce0.67Cr0.33O2.11 being the only compound likes UO2+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 H2 by thermo-splitting of water. An almost stoichiometric amount of H2 (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 CeO2−MOx (Mn, Fe, Cu, and Ni) mixed-oxide solid solutions (O2 evolution ≥1300 °C and H2 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 Ce4+/Ce3+ and Cr4+/6+/Cr3+ redox couples. Compound shows reversible oxygen release and intake by H2O absorption and subsequent hydrogen release to gain parent structure and hence this material can be utilized for generation of H2 at very low temperature by thermo-chemical splitting of water.