269120 Hollow Fe@SiO2 Nanorods for Oxidation-Reduction Chemistry

Monday, October 29, 2012: 9:20 AM
324 (Convention Center )
Hannah Grace, Chemical Engineering, University of Pittsburgh, Pittsburgh, PA, Michelle Najera, Department of Chemical Engineering, University of Pittsburgh, Mascaro Center for Sustainable Innovation, University of Pittsburgh, Pittsburgh, PA and Götz Veser, Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA

Core-shell materials, consisting of a reactive metal core surrounded by an inert support shell are of interest in a range of applications including catalysis, drug delivery, optics, and separation processes.  Hollow core-shell materials, in which there exists a central cavity within the metal core, are of particular interest; they present new possibilities for limiting confinement effects and hence studying the potential for an enhanced reduction-oxidation capacity for the metal cores.  We have developed a synthesis path for hollow iron core/silica shell nanoparticles (Fe@SiO2) with ~40 x 150 nm rod shaped hollow iron cores.  The method begins with a hydrothermal synthesis of β-FeO(OH) nanorods, followed by a wrapping of these particles with a 20-30 nm porous and amorphous silica shell via a modified Stöber synthesis.  This synthesis route relies on the low density of the β-FeO(OH) nanorod intermediate.  The metal core becomes hollow only after transformation into higher density iron materials via calcination in air (to Fe2O3) or reduction (to elemental iron).  We have found that although a range of both hydrothermal and forced hydrolysis synthesis conditions can lead to the β-FeO(OH) intermediate, an optimization of temperature, iron precursor concentration, and pH are required for well-defined and uniform nanorods with narrow particle size distributions. 

Notably, initial evaluation of this material indicates redox capacities ~2 times higher than conventional (non-hollow) Fe@SiO2 materials, possibly due to reduced confinement effects.  Synthesis and characterization of the materials, as well as application as oxygen carriers in chemical looping, a clean combustion technology, will be discussed in detail in the presentation.

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