Study of Surface Reactivity of Cobalt Oxides: Interaction with Methanol

In this paper, the interaction between cobalt oxides (Co 3 O 4 and CoO) and methanol is studied. CoO was obtained by heating under high-vacuum (HV) conditions and characterized by X-ray photoelectron spectroscopy (XPS). The Co 3 O 4 powder sample was characterized by means of XPS, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, X-ray diffraction (XRD), and thermal analysis. The interaction between Co 3 O 4 and methanol was studied both at atmospheric pressure (by means of DRIFT spectroscopy) and under HV conditions (by means of XPS and quadrupolar mass spectroscopy, QMS), whereas the chemisorption of methanol on the CoO surface was studied only under HV conditions. Methanol chemisorbs mainly molecularly on the cobalt oxide surfaces, the alcohol dissociation being more evident at higher temperatures. In the case of Co 3 O 4, the formation of formate and polymers of formaldehyde is evident around 473−523 K, whereas under HV conditions, formaldehyde and several decomposition and fragmentation products were observed as well as carbon oxides. Similar results were obtained in the case of CoO.