High Thermal Stability of La₂O₃- and CeO₂-Stabilized Tetragonal ZrO₂

Catalyst support materials of tetragonal ZrO₂, stabilized by either La₂O₃ (La₂O₃-ZrO₂) or CeO₂ (CeO₂-ZrO₂), were synthesized under hydrothermal conditions at 200°C with NH₄OH or tetramethylammonium hydroxide as the mineralizer. From in situ synchrotron powder X-ray diffraction and small-angle X-ray scattering measurements, the calcined La₂O₃-ZrO₂ and CeO₂-ZrO₂ supports were nonporous nanocrystallites that exhibited rectangular shapes with a thermal stability of up to 1000°C in air. These supports had an average size of 10 nm and a surface area of 59-97 m²/g. The catalysts Pt/La₂O₃-ZrO₂ and Pt/CeO₂-ZrO₂ were prepared by using atomic layer deposition with varying Pt loadings from 6.3 to 12.4 wt %. Monodispersed Pt nanoparticles of 3 nm were obtained for these catalysts. The incorporation of La₂O₃ and CeO₂ into the t-ZrO₂ structure did not affect the nature of the active sites for the Pt/ZrO₂ catalysts for the water-gas shift reaction.