| Abstrakt: |
To thoroughly explore the role of alkaline-earth ions in enhancing the CO 2 methanation performance of LaNiO 3 /dendritic mesoporous silica nanoparticle (DMSN) catalysts, a series of La 1-x A x NiO 3 /DMSN (x = 0, 0.1; A = Ca, Sr, Ba) catalysts was synthesized. XRD analysis revealed the predominant integration of Sr2+ species into the LaNiO 3 crystal lattice, while the Ca2+ and Ba2+-doped samples formed additional crystalline phases of CaO and BaO 2 , respectively. H 2 -TPD results demonstrated that Sr2+ and Ba2+ cations significantly enhanced the dispersion of Ni0 active sites within the catalyst compared to LaNiO 3 /DMSN, contrasting with the effects of Ca2+. Further investigation through H 2 -TPR revealed a more complex reduction process in the Sr2+ and Ba2+-doped samples compared to the bare catalyst. Analysis of O 2 -TPD and CO 2 -TPD data showed a direct relationship between surface oxygen vacancies and moderate alkaline sites, with a more pronounced presence in the Ba2+ and Sr2+-doped samples. The overall activity below 450 °C followed the sequence of La 0.9 Sr 0.1 NiO 3 /DMSN > La 0.9 Ba 0.1 NiO 3 /DMSN > LaNiO 3 /DMSN > La 0.9 Ca 0.1 NiO 3 /DMSN. From the stability perspective, the La 0.9 Ba 0.1 NiO 3 /DMSN catalyst exhibited lower carbon/coke deposition than its Sr2+-promoted counterpart in TGA and Raman analyses. These findings highlighted that the dispersion of Ni0 species and oxygen vacancies emerged as the primary determinants of catalytic activity and stability, respectively. This indicated that while La 0.9 Sr 0.1 NiO 3 /DMSN achieved higher CO 2 conversion and CH 4 selectivity compared to La 0.9 Ba 0.1 NiO 3 /DMSN, it also experienced more carbon/coke deposits, leading to a shorter catalytic lifespan. [Display omitted] • LaNiO 3 /DMSN perovskite-derived catalysts doped with alkaline-earth elements are developed as CO 2 methanation catalysts. • The superior CO 2 methanation activity and selectivity of La 0.9 Sr 0.1 NiO 3 /DMSN is due to its highly dispersed Ni0 species. • La 0.9 Sr 0.1 NiO 3 /DMSN reaches 74.8% CO 2 conversion and 97.8% CH 4 selectivity at 400°C. • The higher CO selectivity of La 0.9 Ba 0.1 NiO 3 /DMSN compared to La 0.9 Sr 0.1 NiO 3 /DMSN is assigned to its higher oxygen vacancy. • The ability of La 0.9 Ba 0.1 NiO 3 /DMSN to mitigate carbon deposition is linked to its high concentration of oxygen vacancies. [ABSTRACT FROM AUTHOR] |
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