Enhancing CO oxidation activity using Re-dispersed Pd-based bimetallic catalysts by hydrothermal treatment

Abstract

Ceria-supported Pd nanoparticles are known as highly active catalysts for automobile emission control system, specifically CO oxidation. The poor activity at cold-start condition should be improved to minimize the emission of pollutants from internal combustion engine-based vehicles. The ratio of surface exposed metal atoms (metal dispersion) should be increased to maximize the use efficiency and mass activity of precious metals. The Pd/CeO$_2$ catalyst often suffers from severe sintering under harsh condition, specifically hydrothermal treatment. Here, we report re-dispersion of Pd-based bimetallic (Pd-Fe, Pd-Ni, and Pd-Co) catalysts deposited on ceria by hydrothermal treatment at 750 ℃ using 10% H$_2$O. The re-dispersion was confirmed by various characterization techniques of transmission electron microscopy, CO chemisorption, CO-diffuse reflectance infrared Fourier transform, CO-temperature programmed desorption, and X-ray absorption spectroscopy. The domain size of Pd was reduced significantly after hydrothermal treatment, with improved CO oxidation activity. The presence of secondary transition metals enhanced the CO oxidation activity further, especially Pd-Fe bimetallic catalyst showed the highest activity for CO oxidation.