Dynamic Stabilization of Metal Oxide-Water Interfaces.
The interaction of water with metal oxide surfaces plays a crucial role in the catalytic and geochemical behavior of metal oxides. In a vast majority of studies, the interfacial structure is assumed to arise from a relatively static lowest energy configuration of atoms, even at room temperature. Using hematite (α-Fe2O3) as a model oxide, we show through a direct comparison of in situ synchrotron X-ray scattering with density functional theory-based molecular dynamics simulations that the structure of the (11̅02) termination is dynamically stabilized by picosecond water exchange. Simulations show frequent exchanges between terminal aquo groups and adsorbed water in locations and with partial residence times consistent with experimentally determined atomic sites and fractional occupancies. Frequent water exchange occurs even for an ultrathin adsorbed water film persisting on the surface under a dry atmosphere. The resulting time-averaged interfacial structure consists of a ridged lateral arrangement of adsorbed water molecules hydrogen bonded to terminal aquo groups. Surface pKaprediction based on bond valence analysis suggests that water exchange will influence the proton-transfer reactions underlying the acid/base reactivity at the interface. Our findings provide important new insights for understanding complex interfacial chemical processes at metal oxide-water interfaces.
Physical Sciences Division, Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
Martin E
0000-0002-7802-3267
ME
McBriarty
Department of Physics and Astronomy, University College London , London WC1E 6BT, U.K.
Guido Falk
0000-0001-7987-4330
GF
von Rudorff
Center for Advanced Radiation Sources, University of Chicago , Chicago, Illinois 60439, United States.
Joanne E
JE
Stubbs
Center for Advanced Radiation Sources, University of Chicago , Chicago, Illinois 60439, United States.
Peter J
PJ
Eng
Department of Physics and Astronomy, University College London , London WC1E 6BT, U.K.
Jochen
J
Blumberger
Physical Sciences Division, Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
Kevin M
0000-0002-8474-7720
KM
Rosso