Alkali metal modified Pt/EG-TiO2 catalysts for CO oxidation with efficient resistance to SO2 and H2O
Catalysis Science & Technology(2024)
Abstract
Pt-0.15Na/EG-TiO2 catalysts obtained by the impregnation method showed better CO oxidation activity as well as resistance to SO2 and H2O than the unmodified Pt/EG-TiO2 catalysts. The physicochemical properties of the catalysts were characterized by means of ICP-AES, TEM, AC-TEM, CO-TPR, ESR, O2-TPD, in situ DRIFTS, XAFS, XRD, BET, SEM and XPS techniques. Meanwhile, the influence of Na doping on improving the CO oxidation activity as well as SO2 and H2O resistance of the Pt/EG-TiO2 catalysts was investigated in depth. The addition of Na promoted the dispersion of Pt nanoparticles (NPs) in the Pt/EG-TiO2 catalysts, which led to the uniform dispersion of Pt on the TiO2 support mainly in the form of nanoclusters and single atoms, thus improving the utilization of Pt. Moreover, it also increased the number of active hydroxyl species on the surface of the Pt/EG-TiO2 catalysts, which accelerated the formation of COO*, an intermediate product of the CO oxidation reaction process, thereby improving the CO oxidation activity of the Pt/EG-TiO2 catalysts. The addition of Na did not change the crystal phase structure and surface morphology of the Pt/EG-TiO2 catalysts; it caused the TiO2 support to have more active hydroxyl species, which reacted with SO2 to form sulfite species. At the same time, the presence of active hydroxyl species inhibited the oxidation of SO2 and reduced the production of sulfate species. Pt–Ox and Na in the Pt-0.15Na/EG-TiO2 catalysts directly interacted with each other and uniformly dispersed on the EG-TiO2 support in the form of Pt–O(OH)x–Na. SO2 was preferentially adsorbed on Na, and then SO2 combined with Na to generate Na2SO4, which led to the localized sulfation of Na in Pt–O(OH)x–Na, reducing the adsorption of SO2 on Pt–O(OH)x–Na. Thus, reduced SO2 adsorption on the Pt and TiO2 support significantly improved the resistance to SO2 and H2O of Pt/EG-TiO2 catalysts.
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