Alkali Metals and Cerium-Modified La–Co-Based Perovskite Catalysts: Facile Synthesis, Excellent Catalytic Performance, and Reaction Mechanisms for Soot Combustion

A series of alkali metals and cerium-modified La–Co-based perovskite catalysts were successfully prepared by a simple method using glucose as a complexing agent. The physicochemical properties of catalysts were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption, H2-temperature-programmed reduction (TPR), O2-temperature-programmed desorption (TPD), soot-TPR, NO-temperature-programmed oxidation (TPO), X-ray photoelectron spectroscopy (XPS), etc. Among the catalysts, La0.9Ce0.05K0.05CoO3 possesses the highest catalytic activity for soot combustion, with T10, T50, and T90 values of 269, 309, and 342 °C, respectively. In the presence of 10% H2O, T90 is significantly reduced to 327 °C. As far as we know, the catalytic performance of the La0.9Ce0.05K0.05CoO3 perovskite oxide catalyst is one of the best results in current reports for soot combustion, especially for T50 and T90. The substitution of A sites by K and Ce ions produces numerous active sites of Co2+–Ov on the surface of the La0.9Ce0.05K0.05CoO3 catalyst and enhances the oxygen storage capacity by redox recycling between Ce4+ and Ce3+. The La0.9Ce0.05K0.05CoO3 catalyst also possesses a stronger ability of NO adsorption, storage, and NO-to-NO2 oxidation compared to other prepared catalysts. Based on the results of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations, Langmuir–Hinshelwood (L–H) and Mars–van-Krevele (MVK) mechanisms were proposed as the main reaction mechanisms for soot combustion. More importantly, the La0.9Ce0.05K0.05CoO3 catalyst exhibits good resistance ability for sulfur and water. These results provide a promising strategy for designing and preparing highly efficient and low-cost catalysts for the practical application of soot particle removal.