Abstract
Through continuous flow reactor experiments, materials characterization, and theoretical calculations, we provide new insights into the reduction of hematite (α-Fe2O3) nanoparticles by methane (CH4) during chemical looping combustion (CLC). Across CLC-relevant temperatures (500–800 °C) and gas flow rates (2.5–250 h–1), decreasing α-Fe2O3 particle size (from 350 to 3 nm) increased the duration over which CH4 was completely converted to CO2 (i.e., 100% yield). We attribute this size-dependent performance trend to the greater availability of lattice oxygen atoms in the near-surface region of smaller particles with higher surface area-to-volume ratios. All particle sizes then exhibited a relatively rapid rate of reactivity loss that was size- and temperature-independent, reflecting a greater role for magnetite (Fe3O4), the primary α-Fe2O3 reduction product, in CH4 oxidation. Bulk (X-ray diffraction, XRD) and surface (X-ray photoelectron spectroscopy, XPS) analysis revealed that oxygen carrier reduction procee...
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