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.
This work was supported by scientific research key project fund of Department of Education of Henan Province (14A150043) and Program for Innovative Research Team in Science and Technology in University of Henan Province (15IRTSTHN003). Y. Yang acknowledges the financial support from the National Research Foundation (NRF), Prime Minister’s Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) program, AcRF Tier 1 grant (RG129/14), Ministry of Education, Singapore, and Agency for Science, Technology and Research (A*STAR), Singapore. We also thank the provision of computing facilities by the A*CRC (A*STAR Computing Resource Center).
Please find the link to the article at the publisher's URL: https://doi.org/10.1016/j.apcata.2016.04.015