Fe2O3/SiO2 nanowires formed by hydrothermally transforming SiO2 spheres in the presence of Fe3+: Synthesis, characterization, and catalytic properties

Abstract

Xie et al. reported that Fe2O3/SiO2 spheres with a surface area of 111m2/g could be hydrothermally transformed into Fe2O3/Silicalite-1 nanowires in the presence of ethylenediamine and triethylamine. The resulting material was found to be active for CO oxidation and N2O decomposition due to the presence of small (1–2nm) Fe2O3 nanoparticles [P.F. Xie et al., Microporous Mesoporous Mater. 200 (2014) 52–60; P.F. Xie et al., J. Mol. Catal. A 409 (2015) 50–58]. In the current work, commercial amorphous SiO2 spheres with a low specific surface area of 9.5m2/g were found to be transformed into amorphous SiO2 nanowires via hydrothermal treatment at 200°C, in the presence of a mixture of ethylenediamine, triethylamine, and Fe(NO3)3, for several days. The Fe3+ species, in the presence of ethylenediamine and triethylamine, not only catalyzed the morphological transformation of SiO2, but also got deposited onto the SiO2 nanowires, forming supported Fe2O3 nanoparticles (2–4nm in diameter) upon subsequent calcination to remove the organic templates. For comparison, Fe2O3/SiO2 spheres prepared by impregnation had big Fe2O3 particles (as large as 50nm). Both the SiO2 supports and supported Fe2O3 particles were characterized by various techniques. The catalytic performance was studied, using N2O decomposition, CO oxidation, and photocatalytic reduction of Cr(VI) as probe reactions. Implications of the findings are discussed.