Thermal stability and propane combustion activity of RhxCe1−xO2−y nanoparticles deposited on functionalized alumina

Abstract

A new, effective method for stabilization of nanoparticles synthesized by the reverse microemulsion method by their deposition on functionalized alumina has been successfully applied for Rh_xCe_1−xO_2−y nanoparticles with a wide range of Rh contents (x ≤ 0.15). Analysis of the as-prepared systems proved that small (<5 nm), homogeneous Rh doped ceria particles, with a large number of structural defects, are uniformly dispersed on the support surface. Unexpectedly, high-resolution HAADF-STEM images also revealed the presence of cerium atoms and their clusters on the alumina support. Rh_xCe_1−xO_2−y nanoparticles on functionalized γ-Al₂O₃ were thermally stable in air up to 800 °C, and their sintering was inhibited more effectively at higher rhodium content. In a reducing atmosphere, the formation of cerium aluminate occurred above 700 °C, and the presence of Rh accelerated the process. Doping of ceria with Rh significantly enhanced ceria reducibility in the low-temperature range (<500 °C), which rose from a few percent for the undoped ceria up to 30 at% for the highest Rh doping. This feature is correlated with the high catalytic activity and stability in the propane combustion process. The temperature of half conversion (T_50%) for the most active Rh_0.15Ce_0.85O_2−y/γ-Al₂O₃ catalyst was 235 °C in the first catalytic cycle and 256 °C in the third cycle.