Synergistic Effects of a CeO/SmMnO-H Diesel Oxidation Catalyst Induced by Acid-Selective Dissolution Drive the Catalytic Oxidation Reaction.

A diesel oxidation catalyst (DOC) is installed upstream of an exhaust after-treatment line to remove CO and hydrocarbons and generate NO. 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 CeO-SmMnO. 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 Mn and Ce cations and the presence of active surface oxygen species. This mechanism benefits the oxygen transformation from Ce to Mn and promotes the Ce + Mn ↔ Ce + Mn 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 CH conversion: = 250 °C) compared to a Pt-based catalyst (CO and CH conversion: = 310 °C) with a WHSV of 120,000 mL g h. Specifically, NO conversion reaches 68% when the temperature is approximately 300 °C.