The Use of the Gliding Arc Plasma Technique to Deposit Fe or Mn Oxides on Fibrous Ceramic Supports for Reactions of Environmental Interest

Abstract

The gliding arc plasma technique (glidarc) was used for the precipitation and deposition ofMn or Fe oxides on zirconia fibers. Two types of fibers were used: commercial (Fib Zr(C))and biomorphic (Fib Zr(B)) ZrO2 fibers, the latter produced using cotton as a biotemplate.Both series of supported catalysts were characterized physicochemically and morphologically.Scanning Electron Microscopy (SEM) analyses showed that Fib Zr(B) largely retainedthe morphology of cotton. Fib Zr(B) presented the tetragonal phase (t-ZrO2), while Fib Zr(C)exhibited the monoclinic phase (m-ZrO2). Using X-ray Diffraction (XRD), the cryptomelanephase (KxMn8O16) was identified only for Mn-Fib Zr(B). In the case of Fe-supported samples,the α-Fe2O3 phase appeared clearly in both biomorphic and commercial fibers. SEMand Transmission Electron Microscopy (TEM) images revealed that the precipitated ironoxides appeared to be better distributed than the manganese oxides, covering the outersurface of the fibrous supports more homogeneously. X-ray Photoelectron Spectroscopy(XPS) confirmed that Mn has an average oxidation state between 3+ and 4+, consistent withthe cryptomelane phase detected by XRD. The synthesized supported systems were testedas catalysts in soot and CO oxidation, with the Mn-supported fibers proving to be moreactive than their Fe-containing counterparts in both reactions.