Thermal Stability and Water Surface Interaction in the Ce_0.95-xTi_xCa_0.05O_1.95 (x=0.05, 0.1) Material System

Today, the use of green renewable energy and its storage and conveyance are of utmost importance, placing the field at the center of technological and scientific inquiry. Of the sustainable energy carriers known to date, reduced reactive gases (i.e., H₂ or CO, or a mixture thereof) is the most promising. Such gases are produced by way of molecular gas (i.e., H₂O or CO₂) reduction/splitting. Cerium dioxide (CeO₂, ceria) is a remarkable material with a unique set of properties, such as a chemically active surface and high ionic conductivity, which allow it to play a significant role in the thermal reduction (splitting) of these gases, thereby reducing the enormous energy requirements of the process. Still, the poor thermal stability of CeO₂ hinders its ability to perform at high temperatures. To resolve this issue, the use of dopants was suggested. In this work, the combined effect of TiO₂ and CaO on the thermal stability of ceria was investigated and will be discussed. Results show that the joint effect of these additives to ceria allows the material to retain its meta-stable solid solution form up to 800 ^oC. At higher temperatures the phase separation into at least two phases occurs, accompanied by rapid coarsening. Once the knowledge base on the thermal stability was established, the water-surface interactions on the solid solution were explored. Exhibiting an increase in water coverage on the material`s surface while lowering the integral heat of adsorption. Making this system attractive for gas splitting thermal applications.