Palladium Nanoparticles Encapsulated in Surface-Defected SBA-15 for Lean Methane Oxidation

Abstract

Mesoporous silica-supported palladium nanoparticles represent promising catalyst materials for lean methane oxidation. However, as only secondary palladium–silica interactions could be generally established in such compounds, active phases would inevitably agglomerate during the long-term reaction and finally result in performance deterioration and poor recyclability. Via the ammonia evaporation (AE) method, we successfully prepared highly active, stable, and recyclable Pd/Santa Barbara amorphous-15 (SBA-15) catalysts for lean methane oxidation. Our Pd/SBA-15-AE catalyst, which not only exhibited excellent catalytic performance for lean methane oxidation (T90 = 335 °C in the first reaction cycle) but also achieved complete methane oxidation at 400 °C in the fifth reaction cycle of the designed test, presented more application potential than its impregnated and ion-exchanged counterparts. Combined with systematic characterizations, the enhanced palladium–silica interaction in AE-prepared catalysts was confirmed and proved to be critical for their excellent catalytic properties. DFT calculations revealed that the binding strength of palladium atoms on the surface-defected silica surface was enhanced when comparing with that on the perfect ones, finally rationalizing the obtained conclusion at the molecular level. The approach proposed in this work to create enhanced metal–support interactions may provide some inspiration for the design of application-oriented palladium catalysts.