Ceria-supported small Pt and Pt3Sn nanoparticles for NOx-assisted soot oxidation

Introduced herein are small Pt and Pt3Sn nanoparticles, stabilized with organosilane or organostannane and impregnated on ceria support, as active sites for NOx-assisted soot oxidation reaction. The catalysts have been tested with four reactions: CO oxidation, NO oxidation, NOx-free soot oxidation and finally NOx-assisted soot oxidation. Our Pt nanoparticles reportedly possess remarkable catalytic activities in CO oxidation, as they actively convert CO at 50 °C, while the alloy Pt3Sn nanoparticles are active at higher temperature. The Pt nanoparticles also mediate more actively NO oxidation than their alloy counterpart, leading to more NO2 production beneficial for soot oxidation. The influence of Pt and Pt3Sn active sites on the catalytic activity during NOx-free soot oxidation becomes less prominent than the morphology, due to the high dependency of the reaction on catalyst structure. The presence of Sn, nevertheless, induces lower oxidation reaction temperature. Finally, in the presence of NOx, the metal active sites undoubtedly boost the catalytic activity of soot oxidation. Pt/CeO2-NC (NC stands for “nanocubes”), reported herein as our most achieving catalyst, demonstrates a remarkable activity, lowering the oxidation temperature at about 80 °C, thanks to the synergy of the active metal nanoparticles and reactive ceria nanocubes. Surprisingly, the catalytic activity of the alloy counterpart (Pt3Sn/CeO2-NC) is close to Pt/CeO2-NC, indicating the potential of the catalyst as an alternative to reducing the employment of precious metal in automotive catalysis. The thermally aged Pt catalysts have demonstrated good resistance to sintering, thanks to the outer protection by silica patches. However, the catalytic activities of the aged Pt3Sn catalysts rely heavily on support morphology.