Improved catalytic performance of Ag-doped K-OMS-2 for soot oxidation

Abstract

The catalytic behaviours of pure K-OMS-2 and Ag-doped K-OMS-2 catalysts (5% Ag doping) synthesized using the hydrothermal method are the focus of investigation in this study. To characterize the catalytic performance of these synthesized catalysts, a combination of analytical techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and Soot Temperature Programmed Reduction (Soot TPR), were employed. The analysis of the prepared samples via XRD revealed a nanocrystalline tetragonal structure, with crystal sizes measuring approximately 22.4 nm. Further examination of the samples using Field Emission Scanning Electron Microscopy (FESEM) unveiled nanorods with dimensions of 213 nm in length and 32 nm in width for K-OMS-2. In comparison, Ag-doped K-OMS-2 displayed nanorods with dimensions of 290 nm in length and 26 nm in width. Notably, the incorporation of Ag+ ions into the K-OMS-2 framework led to an increase in the intensities of the 771 and 527 cm−1 bands when compared to the pure K-OMS-2. This increase can be attributed to the replacement of K+ ions with Ag+ ions in the structure. Furthermore, the introduction of Ag+ ions into the K-OMS-2 framework significantly influenced its catalytic activity for soot oxidation, as evidenced by the augmentation of surface-adsorbed and lattice oxygen radicals, as observed in the results of Soot TPR. The doped sample exhibited substantially enhanced catalytic activity for soot oxidation, as indicated by its low T50 of 370 °C. In addition, the incorporation of the dopant was found to enhance the thermal stability of the catalyst.Graphical abstract