Synthesis in a Glovebox: Utilizing Surface Oxygen Vacancies To Enhance the Atomic Dispersion of Palladium on Ceria for Carbon Monoxide Oxidation and Propane Combustion

Metal dispersion strongly influences the catalytic performance of metal/oxide catalysts, and the surface oxygen vacancies on oxides are capable of strongly interacting with supported metals and enhancing metal dispersion. However, direct utilization of the surface oxygen vacancies on oxides to synthesize highly dispersed metal/oxide catalysts remains as a challenge because of the instability of the surface oxygen vacancies on oxides under ambient conditions. Herein we report a novel approach of “Synthesis in a Glovebox” in which the creation of surface oxygen vacancies on oxides and the subsequent catalyst synthesis are both carried out in a glovebox with O2 concentration lower than 0.1 ppm in order to stabilize the surface oxygen vacancies. Such an approach was applied to synthesize Pd/CeO2 catalysts. Surface oxygen vacancies were created on CeO2 by H2-reduction treatment at various temperatures, and Pd(NO3)2 aqueous solutions were then impregnated onto the reduced supports. It was found that Pd cations preferentially interact with the surface oxygen vacancies, and some get reduced by the surface oxygen vacancies during the impregnation process. Subsequent calcination of Pd(NO3)2/reduced-CeO2 precursors leads to Pd/CeO2 catalysts with a uniform atomically dispersed Pd–O–Ce surface superstructure that can be further utilized to acquire CeO2-supported metallic Pd and CeO2-supported Pd(II) catalysts with enhanced dispersion, activity, and stability, respectively, in CO oxidation and propane (C3H8) combustion reaction. The “Synthesis in a Glovebox” approach conveniently realizes the utilization of surface oxygen vacancies on oxides to enhance the atomic dispersion of supported metals and greatly strengthens the ability to synthesize efficient metal/oxide catalysts.