A supported Ru catalyst was prepared by a galvanic deposition (GD) of Ru on Co particles supported on Al2O3 (Ru/Co-GD). The structure and chemical state of Ru/Co-GD was characterized by using a pulsed CO chemisorption technique, STEM-EDS, XAFS, XPS, CO adsorption FT-IR spectroscopy, and temperature-programed reduction (TPR) method. It is indicated that Ru/Co-GD forms Ru shell on Co nanoparticles. Such a unique structure was not formed on Ru/Co/Al2O3 prepared by a conventional sequential impregnation method (Ru/Co-seq). The Ru shell of Ru/Co-GD showed higher reducibility than Ru species of Ru/Co-seq as well as higher than Ru/Al2O3. Owing to the Ru shell having high reducibility, Ru/Co-GD showed enhanced catalytic activity for NO–C3H6 reaction. In addition, Co oxide on Ru/Co-GD exhibited high catalytic activity for CO and C3H6 oxidation. As a result, Ru/Co-GD showed superior performance for NO–C3H6–CO–O2 reaction compared to the conventional catalysts. The Ru shell structure also contributed to the suppression of Ru vaporization.

A series of ceria‐supported Rh nanoparticles (NPs) that have various particle sizes of 2–7 nm was prepared to investigate the size effect of Rh NPs on NO reduction in NO–CO–C3H6–O2 under stoichiometric conditions. The turnover frequency (TOF) for NO reduction on Rh NPs increased drastically according to their particle size. The strong size dependence of the TOF was attributed to the oxidation states of Rh NPs but not to particle geometries, which include fractions of surface local sites (e.g., corner, edge, plane) and the surface crystal structures (e.g., Rh(1 1 1), (1 0 0)). The variation of the TOF with the Rh metal fraction suggested that Rh metal ensembles are highly active species for NO reduction.