Study of Surface Reactivity of Cobalt Oxides:  Interaction with Methanol

Abstract

In this paper, the interaction between cobalt oxides (Co3O4 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 Co3O4 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 Co3O4 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 Co3O4, 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.

Remote Plasma Atomic Layer Deposition of Co3O4 Thin Films

“…However, the mass density calculated from RBS data and SE film thickness was slightly lower at 5.8 6 0.3 g/cm 3 . These values are in agreement with the Co 3 O 4 bulk density of 6.1 g/cm 3 . X-ray diffraction pattern, presented in Fig.…”

“…The mass density measured by XRR was between 6.1 and 6.4 6 0.3 g/cm 3 showing no clear trend with temperature. However, the mass density calculated from RBS data and SE film thickness was slightly lower at 5.8 6 0.3 g/cm 3 . These values are in agreement with the Co 3 O 4 bulk density of 6.1 g/cm 3 .…”

“…The growth rate was 0.05 nm/ cycle and both the precursor dosing and plasma exposure exhibit saturation after 2 s, all independent of the substrate temperature. This novel combination resulted in the deposition of high density ($5.8 g/cm 3 ), stoichiometric Co 3 O 4 showing a preferential (111) orientation for all temperatures. X-ray diffraction, spectroscopic ellipsometry, and Fourier transform infrared spectroscopy independently indicate an increasing crystallinity with increasing substrate temperature, whereas the surface roughness remains low ( 1 nm).…”

“…CO 2 and H 2 O are detected by mass spectrometry measurements as reaction by-products during the remote O 2 plasma step, revealing a combustion-like reaction process. Cobalt oxides are well-known electrochromic materials that have attracted a lot of attention for applications in smart windows, 1 solar cells, 2 heterogeneous catalysts, 3 and gas sensors. 4 ) is the most stable phase in the Co-O system and adopts a spinel-type cubic structure, unlike the high temperature phase CoO, which crystallizes in a cubic rock salt structure.…”

Application of Laser Ionization Time-of-Flight Mass Spectrometry for the Direct Measurement of a Silane Coupling Agent in Slurries

“…Several analytical techniques are applied to evaluate metal oxide nanoparticles modified with organic compounds, which amounts to thermogravimetric (TG) analysis of the weight of organic coatings [3][4][5] and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy for the analysis of interactions between organic compounds and metal oxides. [5][6][7][8] On the other hand, information directly obtained from slurries, such as viscosity of a slurry 9 and the diameter of particles, 10 is limited at present. Therefore, analytical methods that can offer information of constituents, such as unreacted agents that remain in slurries without pretreatment or separation, are important for a direct understanding of the characteristics of slurries.…”