The Influence of RuO 2 Distribution and Dispersion on the Reactivity of RuO 2 −SnO 2 Composite Oxide Catalysts Probed by CO Oxidation

• Published in: ChemCatChem Vol. 11; no. 10; pp. 2473 - 2483
• Main Authors: Xu, Xianglan, Liu, Fuyan, Huang, Jin, Luo, Wenping, Yu, Jing, Fang, Xiuzhong, Lebedeva, Olga E., Wang, Xiang
• Format: Journal Article
• Language: English
• Published: 20.05.2019
• ISSN: 1867-3880; 1867-3899
• DOI: 10.1002/cctc.201802095

Abstract To elucidate the distribution and dispersion of RuO 2 species on the reactivity, RuO 2 −SnO 2 catalysts with 2 % and 5 % Ru contents have been prepared with impregnation (IMP), deposition‐precipitation (DP) and co‐precipitation (CP) methods, and probed by CO oxidation. With IMP and DP methods, RuO 2 crystallites are predominantly formed on the catalyst surface, which is favorable for CO oxidation. Moreover, the IMP catalyst possesses surface RuO 2 having smaller mean crystallite size and better dispersion than the DP catalyst, thus SnRuO‐IMP displays higher activity than SnRuO‐DP at the same Ru loadings. However, with CP method, RuO 2 species is mainly present as Ru 4+ cations in the lattice of rutile SnO 2 to form a solid solution structure below the lattice capacity, which is less reactive than the surface RuO 2 due to the restriction by the SnO 2 lattice. In conclusion, surface RuO 2 is revealed to be the active species, whose amount and dispersion determine the activity of the catalysts. By changing preparation methods, the distribution of RuO 2 species in the catalysts is varied and impacts the reactivity of the catalysts evidently. The traditional impregnation is found to be the best method to prepare RuO 2 −SnO 2 , which shows the highest activity among all the catalysts.