Synergistic Effects of a CeO₂/SmMn₂O₅-H Diesel Oxidation Catalyst Induced by Acid-Selective Dissolution Drive the...

A diesel oxidation catalyst (DOC) is installed upstream of an exhaust after-treatment line to remove CO and hydrocarbons and generate NO₂. The catalyst should possess both good oxidation ability and thermal stability because it sits after the engine. We present a novel high-performance DOC with high steam resistance and thermal stability. A selective dissolution method is adopted to modify the surface physicochemical environment of CeO₂-SmMn₂O₅. The X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, Raman, electron paramagnetic resonance, hydrogen temperature-programmed reduction, and temperature-programmed desorption results reveal that surface Sm cations are partially removed with the exposure of more Mn⁴⁺ and Ce³⁺ cations and the presence of active surface oxygen species. This mechanism benefits the oxygen transformation from Ce to Mn and promotes the Ce³⁺ + Mn⁴⁺ ↔ Ce⁴⁺ + Mn³⁺ redox cycle according to the in situ near-ambient pressure X-ray photoelectron spectroscopy and in situ diffuse reflectance infrared Fourier transformation spectroscopy results. Under laboratory-simulated diesel combustion conditions, the catalyst demonstrates excellent low-temperature oxidation catalytic activity (CO and C₃H₆ conversion: T₁₀₀ = 250 °C) compared to a Pt-based catalyst (CO and C₃H₆ conversion: T₁₀₀ = 310 °C) with a WHSV of 120,000 mL g^-1 h^-1. Specifically, NO conversion reaches 68% when the temperature is approximately 300 °C.