Bismuth Manganese Catalysts for Soot Oxidation in Diesel Engine Exhaust: Effect of Preparation Methods on Active Oxygen Species

To manufacture efficient and cost-effective catalysts for soot combustion, a series of MnxBiOy catalysts with different molar ratios of manganese bismuth (x=1,3,6,9) were prepared by hydrolysis driven redox, coprecipitation and hydrothermal synthesis methods (named R-MnxBiOy, Cop-MnxBiOy and H-MnxBiOy, respectively). The physicochemical properties of the as-prepared catalysts were characterized via powder X-ray diffraction (XRD), transmission electron microscope (TEM), temperature-programmed reduction by hydrogen (H-2-TPR), X-ray photoelectron spectroscopy (XPS), and so on. The catalytic performance results show that R-Mn3BiOy catalyst obtained by hydrolysis-driven redox method exhibited highest catalytic activity with a maximum concentration of CO2 at 390 degrees C (T-10=330 degrees C, T-50=385 degrees C, and T-90=425 degrees C). Meanwhile, the reaction mechanism of R-Mn3BiOy catalysts was also proposed based on the characterization results. The reason for high catalytic is related to the uniform distribution of Bi on the surface of Mn, which forms more lattice defects, thereby generating a large number of oxygen vacancies and providing more active sites for catalytic reactions. This provides a reference for the design of efficient and stable soot catalysts.