In Situ Grazing-Incidence Extended X-ray Absorption Fine Structure Study of Pb(II) Chemisorption on Hematite (0001) and (1-102) Surfaces

The dominant mode of binding of aqueous Pb(II) to single-crystal (0001) (C-cut) and (1−102) (R-cut) surfaces of α-Fe 2 O 3 has been determined by grazing-incidence X-ray absorption fine structure (GI-XAFS) spectroscopy. Oligomeric Pb(II) complexes were found to bind in inner-sphere modes on both surfaces, which is in contrast with the binding of aqueous Pb(II) on α-Al 2 O 3 (0001) surfaces, where Pb(II) was found in past GI-XAFS studies to bind in a dominantly outer-sphere mode, indicating a significant difference in reactivity of these two surfaces to Pb(II). This difference in reactivity to Pb(II) is explained on the basis of recent crystal truncation rod diffraction studies of the α-Fe 2 O 3 and α-Al 2 O 3 C-cut surfaces in contact with bulk water, which found major structural differences between the surfaces of these two metal oxides.