Highly Active and Stable Palladium Catalysts Supported on Surface-modified Ceria Nanowires for Lean Methane Combustion

Article abstract of DOI:10.1002/cctc.202001438

An efficient strategy was presented to synthesize highly active palladium catalyst supported on ceria nanowires modified by organosilanes (abbreviated as Pd/CeO₂NWs@SiO₂) for lean methane combustion. It is found that such a surface-modified strategy can significantly improve the dispersion of surface palladium species and strengthen the concentration of active surface-adsorbed oxygen species via reconstructing the surface microenvironment, invoking an efficient performance for methane oxidation. Under the space velocity of 60,000 mLg^?1h^?1, 0.5 wt% Pd/CeO₂NWs@SiO₂ displayed extraordinary catalytic activity with 90 % conversion rate at a temperature of around 327 °C, far lower than that of pristine Pd/CeO₂NWs (378 °C) under the same conditions. What's more, unexpected stability was observed under high temperature and the presence of water vapor conditions owing to the intense metal support interaction of Pd/CeO₂NWs@SiO₂ catalyst. The possible reaction mechanism of lean methane oxidation was probed by in situ DRIFT spectra. It is observed that the pivotal intermediate products (carbonate and carbon oxygenates) generated on Pd/CeO₂NWs@SiO₂ surface are more readily decomposed into CO₂. Importantly, the silicon hydroxyl groups (Si?OH) formed during the reaction can efficiently restrict the generation of the stable Pd(OH)_x phase and release more active sites to facilitate the catalytic performance. This study provides a convenient method to design the highly reactive and durable palladium-based catalyst for methane combustion.