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    Tailoring the structure and gas permeation properties of silica membranes via binary metal oxides doping

    Year: 2015

    Journal: RSC ADVANCES, Vol. 5, p 82717-82725, 20170208

    Authors: Ngamou, P. H. Tchoua; Ivanova, M. E.; Herwartz, C.; Luehmann, N.; Besmehn, A.; Meulenberg, W. A.; Mayer, J.; Guillon, O.

    Organizations: Forschungszentrum Julich, Inst Energy & Climate Res, IEK Mat Synth & Proc 1, D-52425 Julich, Germany; Rhein Westfal TH Aachen, Cent Facil Electron Microscopy GFE, D-52056 Aachen, Germany; Forschungszentrum Julich, Cent Inst Engn, ZEA 3, D-52425 Julich, Germany; Forschungszentrum Julich, Ernst Ruska Ctr Microscopy & Spect Electrons ER C, D-52425 Julich, Germany

    The sol-gel method was employed for the synthesis of binary X-Co (X: Mn, Cr) oxide-doped silica membranes with different X/Co molar ratios (X/Co: 0.1, 0.3, 0.9). Single-gas permeation tests were performed at 200 degrees C to determine the effect of the binary oxide composition on the amorphous silica network. The X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM) indicated the presence of smaller MnxCo3-xO4 and CrxCo3-xO4 oxide nanocrystals in the silica matrix in addition to amorphous Co, Mn and Cr species. The H-2/N-2 permeance ratio decreased from (126.3 +/- 9) to (10.7 +/- 2) with an increase in X/Co molar ratio from 0.1 to 0.9 due to the formation of larger pores. However, the binary Co-X oxide-doped silica membrane with the lowest X content showed a H-2/N-2 permeance ratio, (126.3 +/- 9), higher than that, (63.6 +/- 6), of the single cobalt oxide silica membrane. Based on FTIR analysis, it was found that the densification of the membrane at low X content resulted from the formation of silica structures with narrowed siloxane rings. In contrast, the enlargement of siloxane rings due to favorable condensation reactions occurred at high X content.