Tailored synthesis of CoOX thin films for catalytic application

Abstract

Cobalt oxide thin films were systematically synthesized on an inert carrier by pulsed-spray evaporation chemical vapor deposition (PSE-CVD). The effect of substrate temperature on the structure, morphology and surface composition of the prepared films was investigated by XRD, FTIR, SEM and XPS spectroscopies. An in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) and a gas chromatograph (GC) were involved to identify the surface and gaseous species occurring in the total oxidation of propene as a representative of VOCs, respectively. The structural analysis indicated that the obtained thin films transformed from CoO to pure Co₃O₄ spinel as the temperature rose from 350 to 450 °C. A homogeneous grain distribution was observed. For all samples, oxygen was mainly composed of lattice oxygen and adsorbed oxygen constituted a minor proportion. The catalytic tests showed that all the thin films exhibited competitive performances to those of noble metals. According to the observed adsorption peaks of propene at low-temperature and transformation of CoO–Co₃O₄ from the in situ DRIFTS spectra, a combined redox and L–H mechanism was proposed for the catalytic oxidation of propene over cobalt oxide films. The porous structure and adsorbed oxygen on the film surface may well contribute to the catalytic oxidation of propene.