Boosting Methane Combustion over Pd/Y₂O₃-ZrO₂ Catalyst by Inert Silicate Patches Tuning Both Palladium Chemistry and...

Supported palladium (Pd) catalysts are widely utilized to reduce the emission of exhaust CH₄ from lean-burn engines by catalytic combustion. A large amount of water vapor in the exhaust makes hydroxyls accumulate on the catalyst surface at temperatures below 450 °C, leading to severe catalyst deactivation. Tuning palladium chemistry and inhibiting water adsorption are critical to developing active catalysts. Modifying the support surface with inert silicates would both change the palladium-support interaction and decrease water adsorption sites. This study reports an improved Pd/Y₂O₃-ZrO₂ catalyst by constructing silicate patches on yttria-stabilized zirconia (Y₂O₃-ZrO₂) support. The silicates hindered electron transfer from Y₂O₃-ZrO₂ oxygen vacancies to palladium, which optimized palladium chemistry, especially the reducibility of active PdO species, and thereby boosted CH₄ conversion under dry conditions. The temperature of 90% methane conversion (T₉₀) over the catalyst decreased from 386 to 309 °C. Moreover, the inert silicates decreased surface oxygen vacancies of Y₂O₃-ZrO₂ to improve support hydrophobicity, thereby inhibiting hydroxyl accumulation. The poisoning effect of water on the active sites located on the palladium-silicate interface was alleviated. When reaction gases contained 10 vol % water, the silicate-modified catalyst still showed higher activity with T₉₀ of 404 °C, which is lower than T₉₀ of 452 °C for unmodified catalyst. This work represents a step forward in preparing high-performance palladium catalysts for low-temperature wet methane combustion.