Metal Support Interactions in Co3O4/Al2O3 Catalysts Prepared from w/o Microemulsions

Abstract

To obtain nano-sized metal and metal salt crystallites with a narrow size distribution synthesis methods utilizing water in oil (w/o) microemulsions, i.e. reverse micelles, have been widely applied and reported in literature. In this study we show the effect of support addition at different stages of the reverse micelle based preparation of cobalt oxide on alumina model catalysts. All catalysts were characterized with X-ray powder diffraction and Raman spectroscopy indicating the presence of Co 3 O 4 on the Al 2 O 3 support. Studies of the reduction behaviour and X-ray photoelectron spectroscopy however revealed the presence of difficult to reduce cobalt aluminate species in the samples where the support was added during or shortly after the precipitation step in the synthesis process. It can therefore be assumed that if the alumina support is added to the reverse micelle solution unprecipitated Co 2? ions and partially dissolved Al 3? combine and form cobalt aluminates. In the preparations where the solid cobalt precipitates are recovered from the microemulsion and then supported on the carrier, no metal-aluminate formation could be observed. This study therefore gives important information how metal-support interaction can be affected during catalyst preparation using reverse micelles.

Octahedral Co3O4/carbon nanofiber composite-supported Pt catalysts for improved methanol electrooxidation

“…The energy separation between the Co 2p 3/2 and Co 2p 1/2 peaks is $15 eV, in good agreement with a standard Co 3 O 4 sample [10]. The Co 2p 3/2 core levels are mainly observed at $779.9 eV and $780.7 eV, corresponding to the binding energies of Co 3 O 4 and Co(OH) 2 phases [11,12]. In particular, metal-OH species inhibit CO poisoning on the catalyst's surface by oxidizing adsorbed CO to CO 2 [13,14].…”

Surface structure of cobalt, palladium, and mixed oxide‐based catalysts and their activity in methane combustion studied by means of micro‐Raman spectroscopy

“…Furthermore, in a Co‐son/γ‐Al 2 O 3 spectrum (Figure a), a shoulder around 500 cm −1 is formed that is not observed for the reference material. The research groups of Fischer et al and Kock et al correlate this band position with the creation of a CoAl 2 O 4 structure on the surface . It can therefore be concluded that the cobalt atoms could also be adsorbed on the alumina surface and be incorporated into its lattice upon thermal treatment.…”

Visible‐Light‐Driven Water Oxidation with Nanoscale Co3O4: New Optimization Strategies

“…[65] Generally, paramagnetic Co 2 + exhibits more intense satellite peaks than Co 3 + . [66] However, Co 2p spectra of samples synthesized in the presence or absence of H 2 O 2 do not display pronounced differences (see Figure S12, Supporting Information). By contrast, Co 3p spectra of Co 3 O 4 _20 h_H 2 O 2 exhibit a significant broadening and peak shift toward higher bonding energy as compared to Co 3 O 4 _20 h. Two peaks around 62.5 eV and 59.5 eV in the fitted Co 3p spectra can be assigned to Co 3 + and Co 2 + , respectively, and the results clearly demonstrate that the presence of H 2 O 2 during hydrothermal synthesis led to a higher Co 3 + /Co 2 + ratio in Co 3 O 4 _20 h_H 2 O 2 particles ( Figure 10).…”