Effects of K-dopant on structure and activity of KMn/Al2O3 catalysts for CO oxidation: Experimental evidence and DFT calculation

•K-dopant has a great influence on structure and activity of KMn/Al2O3 catalyst.•DFT calculations provide deep insight into the K-doping effect.•K doping activated O2 adsorbed at the O vacancy site and made CO oxidation easier.•This work provides new insights to better understand and design catalyst.

KMn/Al2O3 catalysts with different K:Mn molar ratios were synthesized by a facile impregnation method and attempted for CO oxidation. The correlation in between potassium-dopant amount and the structure/catalytic activity of KMn/Al2O3 catalysts were investigated. Doping small amount of potassium (K:Mn mole ratio less than 1:10) to Mn/Al2O3 catalyst efficiently enhanced the catalytic activity of Mn/Al2O3 catalyst. We found that the K1Mn10/Al2O3 catalyst exhibited the best CO oxidation activity with the TOF of 1.5 × 10−3 s−1 for 100% CO conversion at 260 °C, which is 50 °C lower than that on Mn/Al2O3 catalyst. However, excessive amounts of potassium led to β-to-α-MnO2 phase transformation and poor catalytic performance. DFT calculations combined with multiple characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), O2 temperature-programmed desorption (O2-TPD) and hydrogen temperature-programmed reduction (H2-TPR) were performed to provide a deep insight into the K-doping effect. The results suggested that the addition of an appropriate amount of potassium to Mn/Al2O3 catalyst improved the dispersion of manganese oxide, the mobility and reactivity of surface lattice oxygen, thus significantly improved the catalyst activity.

Graphical abstractK doping induces a structural phase transformation and there is a correlation among doping amount – manganese oxide phases – catalytic performance.Figure optionsDownload full-size imageDownload high-quality image (162 K)Download as PowerPoint slide