Modification of Cobalt Oxide Electrochemically Deposited on Stainless Steel Meshes with Co-Mn Thin Films Prepared by Magnetron Sputtering: Effect of Preparation Method and Application to Ethanol Oxidation

Abstract

Magnetron sputtering is an advantageous method for preparing catalysts supported on stainless steel meshes. Such catalysts are particularly suitable for processes carried out at high space velocities. One of these is the catalytic total oxidation of volatile organic compounds (VOC), economically feasible and environmentally friendly method of VOC abatement. The reactive radio frequency (RF) magnetron sputtering of Mn and Co + Mn mixtures in an oxidation Ar + O2 atmosphere was applied to form additional thin oxide coatings on cobalt oxide layers prepared by electrochemical deposition and heating on stainless steel meshes. Time of the RF magnetron sputtering was changed to obtain MnOx and CoMnOx coatings of various thickness (0.1–0.3 µm). The properties of the supported CoOx-MnOx and CoOx-CoMnOx catalysts were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), temperature programmed reduction (H2-TPR), Fourier-transform infrared (FTIR) and Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The catalytic activity was investigated in the deep oxidation of ethanol, which was employed as a model VOC. According to the specific activities (amount of ethanol converted per unit mass of metal oxides per hour), the performance of CoOx-MnOx catalysts was higher than that of CoOx-CoMnOx ones. The catalysts with the smallest layer thickness (0.1 µm) showed the highest catalytic activity. Compared to the commercial pelletized Co-Mn-Al mixed oxide catalyst, the sputtered catalysts exhibited considerably higher (23–87 times) catalytic activity despite the more than 360–570 times lower content of the Co and Mn active components in the catalytic bed.