The effect of the oxidation states of supported oxides on catalytic activity: CO oxidation studies on Pt/cobalt oxide

Abstract

The strong metal–oxide interaction of platinum nanoparticles (PtNPs) deposited on two types of cobalt oxides, CoO and Co3O4, was investigated using CO oxidation.

Engineering Nanoscale Interfaces of Metal/Oxide Nanowires to Control Catalytic Activity

“…Moreover, the Co 2+ species were preserved before and after the high-temperature CO oxidation (200−240 °C) under O 2 -rich conditions, which is consistent with the previous study of Pt nanoparticles supported on the CoO film. 7,35 Similarly, the XPS spectra of Ti 2p for 1, 2, and 4 layers of the TiO 2 NW with supported 1, 2, and 4 layers of Pt NW (i.e., (Pt/TiO 2 ) 1 , (Pt/TiO 2 ) 2 , and (Pt/TiO 2 ) 4 NW complexes) (Figure S4) show that the dominant oxidation states of TiO 2 NW were Ti 4+ species and were similarly maintained before and after CO oxidation reaction. Also, X-ray diffraction (XRD) patterns indicate that both prepared TiO 2 and CoO nanowires have an amorphous structure, and no significant changes occurred during the CO oxidation in the phase of all of the Pt/oxide NW catalysts.…”

“…The turnover rate and the activation energy obtained from the Arrhenius plot for the layer of Pt NW on the inert SiO 2 substrate showed similar TOF values in previous work on the different sizes of colloidal Pt nanoparticles (NPs) on the SiO 2 substrate 2D catalysts for CO oxidation under the same reaction conditions. 7,46 In addition, a significant increase in catalytic activity and SMSI effect were found when Pt NPs were supported on the TiO 2 and CoO substrates; this differs from the SiO 2 support, which is active for CO oxidation as a result of the participation of lattice oxygen atoms from the surface of transition metal oxides in the oxidation reaction. Consequently, the main result of this experiment is that the Pt NW array cross-stacked on the CoO NW and TiO 2 NW exhibited higher TOF than the Pt NW supported on the SiO 2 substrate, which is ascribed to the different CO oxidation mechanism.…”

“…21,36−38 We have recently demonstrated that the ratio of the interfacial sites to the active metal surface increases with decreasing Pt nanoparticle size, which enhances the catalytic performance of Pt nanoparticles supported on cobalt oxides (CoO and Co 3 O 4 ). 7 In the present work, we demonstrate CO oxidation studies under oxidation conditions for cross-stacked Pt/oxide nanowire complexes fabricated by high-resolution nanotransfer printing, which can effectively tune the number of interfacial sites. 37,39−43 Pt NW arrays were vertically stacked on the two different oxide NW arrays (i.e., TiO 2 or CoO) supported on the silicon dioxide (SiO 2 ) substrate to explore the metal− support interaction.…”

“…10 As a consequence, the interface between metal catalysts and the reducible oxide support is considered the catalytically active site, and the ratio of interfacial sites to the active metal surface area determines the catalytic performance for the CO oxidation reaction. 7,22 On the other hand, the surface of metal species could be changed depending on the reaction conditions (i.e., oxidation or reduction) of the CO oxidation. The surface of platinum group metals can be covered by oxide overlayers (i.e., encapsulation) of the oxide supports, such as TiO 2 , Fe 2 O 3 , and Nb 2 O 5 , under reduction conditions (i.e., excess CO) mainly ascribed to the formation of oxygen vacancies.…”

Advances and Fundamental Understanding of Electrocatalytic Methane Oxidation

“…Reducible ones could easily release oxygen due to the intrinsic capability of the corresponding cations to alter their oxidation state, but nonreducible oxides could not do [77] . Regarding V 2 O 5 and Co 3 O 4 , they are considered to be reducible oxides in terms of vacancy energy formation criterion [78–79] . Therefore, it is reasonable that they are active in EMO where they can release most lattice oxygen atoms allow a degree of methane activation via oxo‐mode.…”