[Zurück]

K. Anic, Ch. Rameshan, A. Bukhtiyarov, H. Li, G. Rupprechter:
"Cobalt Oxide Model Catalyst as Alternative to Noble Metal Catalysts";
Vortrag: 12th Pannonian International Symposium on Catalysis, Castle Trest, Czech Republic; 16.09.2014 - 20.09.2014; in: "12th Pannonian International Symposium on Catalysis", (2014), S. 29.

Abstract
Cobalt oxide has recently turned out to be a novel, highly active heterogeneous catalyst for many
industrial important reactions. Most important, cobalt oxide-based catalysts hold an unique
potential for replacing or reducing the demand for critical materials (noble metals and rare earth
oxides). However the origin of the high cobalt oxide activity in catalysis is still not cleared.
We have chosen a thin cobalt oxide films with a defined structure as model catalysts for low
temperature CO oxidation. The cobalt oxide film was formed on the surface of an Ir(100) single
crystal by physical vapor deposition (PVD) in O2 flow with a subsequent post-oxidation step.
With this routine a 6 ML thick Co3O4(111) and CoO(111) film was prepared. The
characterization of films has been performed by low energy electron diffraction (LEED) and Xray
photoelectron spectroscopy (XPS).
Further we investigated the state of active component and interaction of CO, CO2 and gas
mixture (CO+O2) with different surfaces of cobalt oxide by XPS, polarization modulation
infrared reflection absorption spectroscopy (PM-IRAS) and thermal programmed desorption
(TPD) in the temperature range 200 K - 470 K and in the pressure from UHV to 100 mbar.
It has been shown that CO does adsorb on cobalt oxide films at used temperatures and pressure
ranges. Using XPS and PM-IRAS it has been shown that for both Co3O4(111) and CoO(111),
depending on the conditions of CO adsorption, we obtained appearance of two different carboncontained
species which could be identified as carbonates and elementary carbon. Furthermore in
case of Co3O4(111) film CO adsorption leads to partial reduction of cobalt oxide even at UHV
conditions (pressure of CO in gas phase 1×10-6 mbar) and room temperature. The thermal
stability of carbonates and elementary carbon formed during the CO adsorption on Co3O4(111)
film was investigated by thermo desorption spectroscopy (TDS). It has been shown that both of it
desorbed from the surface at 520 K -700 K as CO2, at the same time Co3O4(111) film has been
reduced to CoO(111).
Also it was shown that it is possible to recover the film (initial state of composition and structure)
after CO adsorption and desorption experiments by oxidation treatment at 550 K and a
subsequent annealing at UHV to 670 K.
Acknowledgement
This work was financially supported by the Austrian Science Fund (FWF) through Grant
Number: International Program I1041