The behavior of H2O molecules confined on surface of metal oxides is a fascinating subject which readily relates to popular concerns such as heterogeneous catalysis, protein folding, environmental remediation, mineral growth and dissolution, and light-energy conversion in solar cells. The present study of interaction between H2O and SnO2 surfaces addresses such fundamental issues at atomic scale and reinforces our understanding of the strength of the surface hydrogen bonds, which is at the core of determining the structure, the dynamics, and the physical and chemical properties of the interface. Results from inelastic neutron scattering and ab-initio molecular dynamics provide evidence that the strong surface hydrogen bonds drive H2O dissociation at the interface and decouple the hydrated SnO2 surfaces from additional H2O molecules due to an epitaxial screening of the inner H2O/OH layers in registry with the substrate structure. Neutron total (elastic) scattering and accompanying molecular modeling indicate the highly structured interfacial H2O/OH layers, which not only stabilize the host phase as nanoparticles but also induce particle-size-dependent structural modifications. The minimum concentration of OH groups required to prevent rapid growth of nanoparticles during thermal dehydration corresponds to ~0.7 monolayer coverage. These newly observed results and analyses provide an excellent example on the role of surface confined H2O molecules. The outcome of the study is potentially significant in understanding the net reactive properties of the host materials and the effective hydrophilic interactions at molecular level.

Structure and dynamics of the surface-water on SnO<sub>2</sub> nanocrystals

247th National Meeting (2014)

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Structure and dynamics of the surface-water on SnO2 nanocrystals

Structure and dynamics of the surface-water on SnO₂ nanocrystals