Controlling the metal–support interaction with steam-modified ceria to boost Pd activity towards low-temperature CO oxidation

Abstract

The performance of cerium-based composite catalysts can be improved by regulating the metal–support interaction (MSI) through the modification process. Unlike common steam post-modification, this study reveals that the steam treatment of the ceria support before loading palladium can significantly reduce the activation energy (11.6 kJ mol⁻¹) of the composite catalyst (Pd_A-ST) for CO oxidation, and achieve high catalytic activity at low temperature (9.72 mol_CO h⁻¹ g_Pd⁻¹, 27 °C). Thermally stable hydroxyl groups (OH) are generated on the ceria surface due to the dissociation of high-temperature steam at oxygen vacancies. The OH-modified ceria affects the loaded palladium in three aspects, including MSI enhancement, metal dispersion promotion and the binding energy shift of active Pd²⁺ species. Strong MSI often causes strong CO adsorption, resulting in catalyst poisoning at low temperatures. However, low binding strength between palladium and CO molecules was found in this study, leading to high catalytic activity at low temperature. This study provides an example of the regulation of MSI to obtain high-performance catalysts and demonstrates the potential of developing effective catalysts for low-temperature catalytic reactions.