Palladium Nanoparticles Supported on Surface-Modified Metal Oxides for Catalytic Oxidation of Lean Methane

Abstract

Palladium nanoparticles (NPs) were successfully deposited on surface-modified metal oxides (mod-MOx, M = Hf, Ti, Zr, Ce, and Al) and applied as catalyst materials for lean methane combustion. It was found that the surface modification of support materials improved the light-off performance of 1.0Pd/mod-HfO2 (palladium catalyst supported on surface-modified HfO2 with a content of 1.0 wt %), 1.0Pd/mod-ZrO2, and 1.0Pd/mod-CeO2, but lowered the purification efficiency of 1.0Pd/mod-TiO2 and 1.0Pd/mod-Al2O3 when compared with their 1.0Pd/MOx counterparts. Over the best-performing 1.0Pd/mod-HfO2 material, 90% of methane was removed at 317 °C and a space velocity of 60 000 mL g–1 h–1, which was 120 °C lower than that required for the untreated 1.0Pd/HfO2 sample. Detailed characterization of representative HfO2-related materials showed that the introduced silicon modifier materials, which existed as an amorphous phase covering the HfO2 surface, could improve the dispersion of palladium nanoparticles due to their steric confinement and strengthen the generation of surface-adsorbed oxygen species via electron transfer. We believe that this surface modification strategy, which could promote the catalytic performance of palladium nanoparticles supported on other cost-effective host materials as well, provides a feasible method for the design of methane combustion catalysts with excellent low-temperature performance.