One-Dimensional Ceria as Catalyst for the Low-Temperature Water−Gas Shift Reaction

Abstract

Synchrotron-based in situ time-resolved X-ray diffraction and X-ray absorption spectroscopy were used to study pure ceria and Pd-loaded ceria nanotubes and nanorods (1D-ceria) as catalysts for the water−gas shift (WGS) reaction. While bulk ceria is very poor as WGS catalysts, pure 1D-ceria displayed catalytic activity at a temperature as low as 300 °C. The reduction of the pure 1D-ceria in pure hydrogen started at 150 °C, which is a much lower temperature than those previously reported for the reduction of 3D ceria nanoparticles. This low reduction temperature reflects the novel morphology of the oxide systems and may be responsible for the low-temperature WGS catalytic activity seen for the 1D-ceria. Pd-loaded 1D ceria displayed significant WGS activity starting at 200 °C. During pretreatment in H2, the ceria lattice parameter increased significantly around 60 °C, which indicates that Pd-oxygen interactions may facilitate the reduction of Pd-loaded 1D-ceria. Pd and ceria both participate in the formation of the active sites for the catalytic reactions. The low-temperature hydrogen pretreatment results in higher WGS activity for Pd-loaded 1D-ceria.