Hydrogen interaction with Pd/Ce0.8Zr0.2O2 nanocomposites prepared by microemulsion, coprecipitation and supercritical CO2 treatment

Nanocrystalline Ce0.8Zr0.2O2 solid-solutions (CZ) were synthesized by microemulsion (ME80). co-precipitation (CP80) and co-precipitation followed by supercritical CO2 post-treatment (SC80). Structural, microstructural and textural characterizations of oxides were performed and correlated with their redox properties. The results are consistent with the formation of solid solutions with high surface area (S-BET similar to 200 m(2) g-(1)), constituted by nanoparticles (4-6 nm) with a fluorite type structure but different mesoporosity. Dynamic oxygen storage capacity (OSC) measurements indicate that the presence of Pd improves the extension of reduction of CZ support, with the higher low-temperature OSC capacity observed for Pd/SC80. Static kinetics measurements, confirm that Pd promotes hydrogen spillover onto CZ favoring both surface and bulk reduction of Ce(IV) to Ce(III) even at 373K. Pd/5C80 presents considerably higher total OSC (691 versus 400-454 mu mol H-2 g(-1)) with respect to the other samples. Significant Pd sintering was observed over Pd/ME80 only, with the consequent decrease of redox capability for Pd/ME80 catalyst. On the contrary. Pd/CP80 and Pd/SC80 samples presented highly dispersed Pd and good stability after redox cycling. These findings indicate that CP followed by thermal treatment under supercritical conditions is a promising method to synthesize materials with high low temperature OSC and promissory redox properties due to improved Pd/CZ interaction. (C) 2011 Elsevier B.V. All rights reserved.