X射线光电光谱表征金属氧化物的酸碱性

Characterizing the surface chemistry of oxides with X-ray photoelectron spectroscopy:Comparison of oxygen valence charge in octahedrally and tetrahedrally O coordinated metal ions and acid-base properties

本文探讨了氧配位的八面体及四面体的金属配合物中氧原子的价态变化及其酸碱性差异之间的关系。首先利用X射线光电光谱(XPS)分别推导出了氧原子在碱及碱土铝酸盐、铬酸盐、高铁酸盐、钼酸盐及钨酸盐中的价态,随后对氧原子的价态及氧化物的酸碱性质进行了比较。研究结果表明,氧原子的价态在这两种配位构型的化合物中没有显著的差别,其酸碱性的不同在于四面体配位的金属化合物中O2p态在非成键和成键的电子密度中高价带的分裂。

XPS derived O charge has been compared for the alkali and alkaline earth aluminates, chromates, ferrates, molybdates, and tungstates, relative to the O charges for the single oxides, to test whether a significant shift in overall charge exists between 4- and 6-fold O coordinated metal ions. We find that coordination change tends not to affect the O charge significantly. The large chemical differences associated with coordination change must be attributed to the splitting up of the top of the valence band of the O2p states in non-bonded and bonded electron density in the tetrahedrally coordinated complexes.