Effects of the Metal–Support Interaction in Ru/CeO₂ Nanostructures on Active Oxygen Species for HCHO/CO Oxidation

Abstract

Catalysts comprising Ru supported on CeO 2 with different morphologies have been widely investigated in various reactions, and the Ru/CeO 2 -nanorod catalysts have generally demonstrated higher performance. The strong interaction between Ru and CeO 2 nanorods, which is beneficial to oxygen activation, is usually considered to be responsible for the higher oxidation activity of the Ru/CeO 2 nanostructures. However, how the metal−support interaction of Ru/CeO 2 affects the activation of oxygen species still remains elusive. In this work, we prepared two nanostructures consisting of Ru supported on CeO 2 nanorod (NR) and nanocube (NC), and the Ru/CeO 2 -NR catalyst exhibited higher catalytic activity than Ru/CeO 2 -NC in the oxidation of formaldehyde (HCHO) and carbon monoxide (CO) at low temperatures. The results of complementary characterization techniques revealed that the interaction between Ru and CeO 2 -NC is actually stronger than that of Ru/CeO 2 -NR, and more interestingly, we observed that the different Ru−CeO 2 interactions induce distinct active oxygen species responsible for the oxidation reactions over Ru/CeO 2 -NR and Ru/CeO 2 -NC. The stronger interaction between Ru and CeO 2 -NC leads to the activation of lattice oxygen on CeO 2 -NC and a weakened redox capacity of RuO x species. In contrast, the moderate interaction between Ru and CeO 2 -NR induces a higher redox capacity of RuO x species but weak activation of lattice oxygen on CeO 2 -NR. The active RuO x on Ru/CeO 2 -NR is identified as being responsible for the high activity for HCHO/ CO oxidation, while the activated lattice O of CeO 2 -NC in the Ru−CeO 2 interfacial domain is the active species on Ru/CeO 2 -NC, rather than RuO x , resulting in low activity. These findings on Ru/CeO 2 nanostructures provide insight into understanding the metal−support interaction over Ru/CeO 2 catalysts.

Low Temperature NO and CO Conversion with a Mechanistic Approach on Ru-Composed Cerium Oxide

“…Studies indicate that the introduction of ruthenium enhances the reactivity of the catalyst, leading to the formation of Ru−O−Ce bonds, which are essential for catalytic oxidation reactions. 39 Further, increase in the Ru in ceria (Ce 0.95 Ru 0.05 O 2 ) showed the highest oxygen release at 81 and 125 °C, which was observed to be a great achievement obtained within the series of the catalysts prepared with respect to temperature. This shifting of the reduction pattern by addition of Ru is mainly due to weakening of Ce−O bond on Ru doping, which alters the mobility of oxygen and also its redox character.…”

“…The incorporation of Ru species into CeO 2 -based catalysts has a notable impact on oxygen mobility and catalytic performance. Studies indicate that the introduction of ruthenium enhances the reactivity of the catalyst, leading to the formation of Ru–O–Ce bonds, which are essential for catalytic oxidation reactions …”

Oxidative Redispersion-Derived Single-Site Ru/CeO2 Catalysts with Mobile Ru Complexes Trapped by Surface Hydroxyls Instead of Oxygen Vacancies

“…Notably, distinguished from the limited oxidation activity of the square-planar Pt 1 structure, , the Ru 1 /CeO 2 -step structure was reminiscent of the 1f-cus Ru sites on the RuO 2 surfacethe workhorse active sites for most oxidation reactions. , As a result, H400+O and H500+O exhibited superior performance for C 3 H 6 and CO catalytic combustion (Figure and Figure S19). Similarly, Qin et al have reported that the atomically dispersed O–Ru–O on CeO 2 (111) could accelerate the low-temperature oxidation reactions . The higher oxygen lability of these fully dispersed Ru–O x species than clustered RuO 2 was also identified via H 2 -TPR and was correlated with the catalytic activity of Ru/CeO 2 for propylene, acetic acid, and soot combustion. − Therefore, it was unnecessary for the Ru 1 /CeO 2 -step structure to be deoxidized (i.e., Ru–O x → Ru) to become catalytically reactive.…”

“…Similarly, Qin et al have reported that the atomically dispersed O−Ru−O on CeO 2 (111) could accelerate the low-temperature oxidation reactions. 100 The higher oxygen lability of these fully dispersed Ru−O x species than clustered RuO 2 was also identified via H 2 -TPR and was correlated with the catalytic activity of Ru/CeO 2 for propylene, acetic acid, and soot combustion. 101−103 Therefore, it was unnecessary for the Ru 1 /CeO 2 -step structure to be deoxidized (i.e., Ru−O x → Ru) to become catalytically reactive.…”

Highly active low-temperature HCHO oxidation of mesoporous Pt/CeO2 derived from Pt/CeBDC

“…As a typical reductive metal oxide, CeO 2 's boundary with a noble metal is considered to be a low-temperature catalytically active site in many reaction systems. 15,18,21 Therefore, the catalytic activity of formaldehyde oxidation by a CeO 2 -supported catalyst can theoretically be improved by increasing the boundary between CeO 2 and metal.…”