Low-temperature activity of Pd/CeO2 catalysts: Mechanism of CO interaction and mathematical modelling of TPR-CO kinetic data

We studied the kinetic of CO interaction with Pd/CeO2 catalysts during temperature programmed reactions (TPR-CO). Increasing of the calcination temperature leads to the changes of palladium states in the catalysts structure from solid solution to surface clusters and nanoparticles. Kinetic simulation showed that surface clusters are the most active species at temperatures below 100 degrees C. The blurry CO2 evolution in the temperature range 100-250 degrees C is determined by the effect of bulk-surface transfer of lattice oxygen to the surface clusters. The separate sharp peak at 200 degrees C was simulated to be attributed to the reduction of the nanoparticles. In the high-temperature range of TPR-CO the reduced active centres on the surface of ceria are supplied with oxygen from the ceria bulk. Upon increasing the calcination temperature, the concentration of active oxygen in the ceria lattice taking part in the reaction with CO increases, and the catalyst is more reduced. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study focused on the kinetics of CO interaction with Pd/CeO2 catalysts under temperature programmed reactions (TPR-CO). As the calcination temperature increases, the palladium states in the catalyst structure transition from solid solution to surface clusters and nanoparticles. Surface clusters are found to be the most active species at temperatures below 100 degrees C, while the bulk-surface transfer of lattice oxygen to the surface clusters contributes to CO2 evolution in the temperature range 100-250 degrees C. Additionally, the reduction of nanoparticles is attributed to a separate sharp peak at 200 degrees C. In the high-temperature range of TPR-CO, active oxygen on the surface of ceria is supplied from the ceria bulk, and increasing the calcination temperature results in a higher concentration of active oxygen in the ceria lattice.