Enhanced catalytic activities and selectivities in preferential oxidation of CO over ceria-promoted Au/Al2O3 catalysts

Abstract

The preferential oxidation of CO (CO-PROX) is a hot topic because of its importance in proton-exchange membrane fuel cells (PEMFCs). Au catalysts are highly active in CO oxidation. However, their activities still need to be improved at the PEMFC operating temperatures of 80–120 °C. In the present study, Au nanoparticles of average size 2.6 nm supported on ceria-modified Al2O3 were synthesized and characterized using powder X-ray diffraction, nitrogen physisorption, transmission electron and scanning transmission electron microscopies, temperature-programmed hydrogen reduction (H2-TPR), Raman spectroscopy, and in situ diffuse-reflectance infrared Fourier-transform spectroscopy. Highly dispersed Au nanoparticles and strong structures formed by Au–support interactions were the main active species on the ceria surface. The Raman and H2-TPR results show that the improved catalytic performance of the Au catalysts can be attributed to enhanced strong metal–support interactions and the reducibility caused by ceria doping. The formation of oxygen vacancies on the catalysts increased their activities in CO-PROX. The synthesized Au catalysts gave excellent catalytic performances with high CO conversions (> 97%) and CO2 selectivities (> 50%) in the temperature range 80–150 °C.