| AVS 56th International Symposium & Exhibition | |
| In Situ Microscopy and Spectroscopy: Interfacial and Nanoscale Science Topical Conference | Thursday Sessions |
| Session IS+AS-ThA |
| Session: | In-Situ Microscopy and Spectroscopy: Surface Reactions |
| Presenter: | J.-H. Guo, Lawrence Berkeley National Laboratory |
| Correspondent: | Click to Email |
Solar energy can be converted to electricity and chemical fuels for energy use and storage. However, the cost and conversion efficiency have been the biggest challenge for potential use of solar energy. There are the emerging technologies of using semiconductors for light harvesting assemblies; and charge transfer processes to solar cells. It could provide a significant contribution to our electrical and chemical resources if efficient and inexpensive systems utilizing readily available materials could be devised for the conversion process.
This presentation will shade some light on synchrotron radiation based soft-x-ray spectroscopy study of nanostructured materials. Soft-x-ray absorption probes the local unoccupied electronic structure (conduction band); soft-x-ray emission probes the occupied electronic structure (valence band); and the addition of resonant inelastic soft-x-ray scattering (Raman spectroscopy with soft x-rays) can tell the energy levels that reflect the chemical and physical properties of semiconductors. The experimental studies suggest that in-situ photon-in/photon-out soft-x-ray spectroscopy becomes an emerging tool for investigating the surface and interface science.
(1) The examples show quantum size effects on the exciton and band-gap energies of semiconductor nanocrystals (Hematite nanoarrays). Such finding strongly suggests that such designed nanomaterials could meet the bandgap requirement for the photocatalytic oxidation of water without an applied bias.
(2) The storage of hydrogen in a both safe and compact manner is of great importance for, for example, hydrogen powered vehicles. We have explored in-situ photon-in/photon-out soft-X-ray spectroscopy to study the molecular adsorption of H2 on SWNTs under ambient pressures. The spectral changes with the increasing gas pressures provide the strong evidences for the tube-wall structure deformation and possibly a fraction of charge transfer due to the gas collision.