Nature of the chemical bond between metal atoms and oxide surfaces: New evidences from spin density studies of K atoms on alkaline earth oxides

被引:76
作者
Chiesa, M
Giamello, E
Di Valentin, C
Pacchioni, G
Sojka, Z
Van Doorslaer, S
机构
[1] Univ Turin, Dipartimento Chim IFM, I-10125 Turin, Italy
[2] Univ Turin, NIS Ctr Excellence, I-10125 Turin, Italy
[3] Univ Milano Bicocca, Dipartimento Sci Mat, I-20125 Milan, Italy
[4] Jagiellonian Univ, Dept Chem, PL-30060 Krakow, Poland
[5] Jagiellonian Univ, Reg Lab Physicochem Anal & Struct Res, PL-30060 Krakow, Poland
[6] Univ Instelling Antwerp, Dept Phys, Lab Spect Biophys & Catalysis, B-2610 Antwerp, Belgium
关键词
D O I
10.1021/ja0542901
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
We have studied the interaction of K atoms with the surface of polycrystalline alkaline-earth metal oxides (MgO, CaC, SrO) by means of CW- and Pulsed-EPR, UV-Vis-NIR spectroscopies and DFT cluster model calculations. The K adsorption site is proposed to be an anionic reverse corner formed at the intersection of two steps, where K binds by more than 1 eV, resulting in thermally stable species up to about 100 K. The bonding has small covalent and large polarization contributions, and the K atom remains neutral, With one unpaired electron in the valence shell. The interaction results in strong modifications of the K electronic wave function which are directly reflected by the hyperfine coupling constant, (K)a(iso). This is found to be a very efficient "probe" to measure the degree of metal-oxide interaction which directly depends on the Substrate basicity. These results provide an original and general model of the early stages of the metal-support interaction in the case of ionic oxides.
引用
收藏
页码:16935 / 16944
页数:10
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