Chemistry at corners and edges: Generation and adsorption of H atoms on the surface of MgO nanocubes
- Department of Chemical Physics, Fritz-Haber-Institute of the Max-Planck-Society, Faradayweg 4-6, D-14195 Berlin (Germany)
We used UV light to generate site-selective O{sup -} hole centers at three-coordinated corner oxygen sites on MgO nanocubes. These highly reactive O{sup -} radicals split H{sub 2} homolytically and, in the course of this reaction, become hydroxylated and produce hydrogen atoms. The hydrogen atoms adsorb predominantly at cube edges and dissociate into surface-trapped electrons and protons. We propose that the experimentally observed (H{sup +})(e{sup -}) centers are formed adjacent to the hydroxyl groups generated in the homolytic splitting process and can be defined as (H{sup +}){sub 3C}{center_dot}{center_dot}{center_dot}(e{sup -})(H{sup +}){sub NC} centers where 3C and NC refer to the coordination numbers of the corresponding hydroxylated oxygen sites. Our ab initio embedded cluster calculations reveal that the electronic properties of (H{sup +}){sub 3C}{center_dot}{center_dot}{center_dot}(e{sup -})(H{sup +}){sub 4C} centers situated along MgO nanocube edges are consistent with both the electron-paramagnetic-resonance signal parameters and the reported optical-absorption properties. The transformation of corner O{sup -} centers into the (H{sup +}){sub 3C}{center_dot}{center_dot}{center_dot}(e{sup -})(H{sup +}){sub NC}-type centers prevents their recombination with electronic surface centers and, hence, significantly alters the electronic structure of MgO nanocubes by introducing shallow electron traps.
- OSTI ID:
- 20723023
- Journal Information:
- Journal of Chemical Physics, Vol. 123, Issue 6; Other Information: DOI: 10.1063/1.1997108; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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