Effect of exposed facets and oxygen vacancies on the catalytic activity of PdxCe1-xO2-δ catalysts: a combined experimental and theoretical study

The effect of exposed facets and oxygen vacancies on the catalytic activity of PdxCe1-xO2-delta nanorods for low-temperature CO oxidation has been investigated based on both experimental and theoretical methods. PdxCe1-xO2-delta nanorods with exposed {100} and {110} facets are more active than those with the {111} facet, and such superior active facets can become selectively accessible by modulating the calcination temperature. Moreover, a post H-2 reduction process further enhances the low temperature activity of PdxCe1-xO2-delta composites with a CO initial conversion temperature as low as 24 degrees C. It is suggested that the enhanced activity by the H-2 reduction process is mostly attributed to the promotion of oxygen vacancy concentration on the exposed facets. This is in reasonable agreement with the theoretical prediction that the CO oxidation proceeds via an oxygen vacancy-mediated Eley-Rideal mechanism on PdxCe1-xO2-delta nanorods. Our work highlights the importance of both exposed facets and oxygen vacancies on low temperature CO oxidation for PdxCe1-xO2-delta nanorod catalysts.