Low-temperature CO oxidation by Pd/CeO2 catalysts synthesized using the coprecipitation method

Pd/CeO 2 catalysts synthesized using the coprecipitation method under a wide range of palladium loading and calcination temperatures were investigated in this study. Structural (XRD, TEM), spectroscopic (XPS) and kinetic (TPR-CO) methods were used to investigate the morphological and structural forms of the catalysts and identify the states of palladium as the active component on the CeO 2 surface and in its bulk. It was found that the synthesis and subsequent calcination at 450 °C resulted in the formation of two main types of the catalyst components: PdO nanoparticles and Pd x Ce 1− x O 2− δ solid solution. Application of HRTEM allowed to establish the formation of aggregates where ceria or Pd x Ce 1− x O 2− δ nanoparticles were located around PdO nanoparticles. A subsequent calcination process resulted in partial dissolution of PdO nanoparticles in ceria lattice and formation of the surface compounds of palladium and ceria, PdO x (s)/Pd–O–Ce(s), which contain high reactive oxygen according to the TPR-CO data. Based on the XPS and TPR-CO data the catalytic activity at low temperatures ( x (s)/Pd–O–Ce(s) and palladium ions Pd 2+ in the Pd x Ce 1− x O 2− δ bulk phase.