HYDROGEN EVOLVING REACTIONS - THERMAL DECOMPOSITIONS OF CEROUS CARBONATES

Thermal decomposition studies of Ce2(CO3)3·8H2O and CeOHCO3·xH2O under a variety of experimental conditions demonstrate quantitative oxidation to CeO2 at 873 K. Gaseous decomposition products include H2, CO and CO2, the quantity of each being dependent on the amount of water present during the decomposition. Small amounts of CH4 also are produced. Mechanistic studies based on X-ray powder diffraction data have elucidated the primary oxidation pathway to be evolution of carbon monoxide from Ce2O2CO3. Hydrogen is produced via the water-gas shift reaction. Equilibrium data indicate that CeO2 exhibits catalytic activity with respect to this reaction. Identification of hydrogen as a reaction product makes the Ce2O2CO3 oxidation reaction desirable for inclusion in thermochemical cycles for water splitting, since it is non-corrosive. Another advantage is the capability of manipulating the CO:H2 ratio in the product gas mixture so that introduction to a suitable catalyst will yield methane, methanol or higher hydrocarbons. © 1978.