Nano-structured CeO2 supported Cu-Pd bimetallic catalysts for the oxygen-assisted water-gas-shift reaction

The present work focuses on the development of novel Cu-Pd bimetallic catalysts supported on nano-sized high-surface-area CeO2 for the oxygen-assisted water-gas-shift (OWGS) reaction. High-surface-area CeO2 was synthesized by urea gelation (UG) and template-assisted (TA) methods. The UG method offered CeO2 with a BET surface area of about 215 m2/g, significantly higher than that of commercially available CeO2. Cu and Pd were supported on CeO2 synthesized by the UG and TA methods and their catalytic performance in the OWGS reaction was investigated systematically. Catalysts with about 30 wt% Cu and 1 wt% Pd were found to exhibit a maximum CO conversion close to 100%. The effect of metal loading method and the influence of CeO2 support on the catalytic performance were also investigated. The results indicated that Cu and Pd loaded by incipient wetness impregnation (IWI) exhibited better performance than that prepared by deposition-precipitation (DP) method. The difference in the catalytic activity was related to the lower Cu surface concentration, better Cu-Ce and Pd-Ce interactions and improved reducibility of Cu and Pd in the IWI catalyst as determined by the X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) studies. A direct relation between BET surface area of the CeO2 support and CO conversion was also observed. The Cu-Pd bimetallic catalysts supported on high-surface-area CeO2 synthesized by UG method exhibited at least two-fold higher CO conversion than the commercial CeO2 or that obtained by TA method. The catalyst retains about 100% CO conversion even under extremely high H2 concentration.