2014年6月英语四级作文真题附范文(第2套):A Beautiful City in China

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As shown in Figs. 5 and 6, the peaks at 532.5 and 533.1 eV in the XPS spectrum of O1s in the complex support (Fig. 5a) are assigned to lattice oxygen and adsorbed oxygen in –OH groups on the surface, respectively. The binding energy of adsorbed oxygen increases after introducing Cu(acac)2 (Figs. 5b). However, the binding energies at 933.2 eV (Fig. 6) assigned to Cu2p3/2 of the supported catalyst shift to lower values compared to that of Cu2p3/2 of Cu(acac)2 at 934.5 eV [35]. The change in the binding energies reveals that there is a possible electronic interaction between Cu2 and hydroxyl, in which O atom donates electron to Cu2 , possibly giving positive effect on the activity of supported catalyst. As a result, the binding energy of O1s shifts towards higher value while Cu2p3/2 to lower value [36].