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

Xie et al. reported that Fe 2 O 3 /SiO 2 spheres with a surface area of 111   m 2 /g could be hydrothermally transformed into Fe 2 O 3 /Silicalite-1 nanowires in the presence of ethylenediamine and triethylamine. The resulting material was found to be active for CO oxidation and N 2 O decomposition due to the presence of small (1–2   nm) Fe 2 O 3 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 SiO 2 spheres with a low specific surface area of 9.5   m 2 /g were found to be transformed into amorphous SiO 2 nanowires via hydrothermal treatment at 200   °C, in the presence of a mixture of ethylenediamine, triethylamine, and Fe(NO 3 ) 3 , for several days. The Fe 3+ species, in the presence of ethylenediamine and triethylamine, not only catalyzed the morphological transformation of SiO 2 , but also got deposited onto the SiO 2 nanowires, forming supported Fe 2 O 3 nanoparticles (2–4   nm in diameter) upon subsequent calcination to remove the organic templates. For comparison, Fe 2 O 3 /SiO 2 spheres prepared by impregnation had big Fe 2 O 3 particles (as large as 50   nm). Both the SiO 2 supports and supported Fe 2 O 3 particles were characterized by various techniques. The catalytic performance was studied, using N 2 O decomposition, CO oxidation, and photocatalytic reduction of Cr(VI) as probe reactions. Implications of the findings are discussed.