Insertion of Fe2O3 nanoparticles in SBA-15 mesopores and evaluation of their textural and redox characteristics

Nanometric Fe(III) oxide particles could be inserted inside the internal pore volume of SBA-15 mesoporous silica when Fe(III) chelates (EDTA, gluconate and citrate-NH4) were used as impregnating precursors. Fe(III) nitrate preferentially yields 8 nm uniformly sized Fe2O3 clusters that selectively plug the SBA-15 channels. The control of the size and dispersion of the Fe2O3 particles generated after subsequent oxidative degradation of the chelates was shown to be dependent of the nature (geometry) of the complex used, that preferentially interacts with the SBA-15 internal walls that exhibit a high curvature (confinement effect). Cyclic voltammetry along with TPR, was used to evaluate the redox properties of Fe(III) species in the final composites, arguing in all cases for a partial reduction of Fe2O3 to FeO and for a strong interaction with the silica support of the very small Fe2O3 particles resulting from the decomposition of Fe-EDTA.