Keller Daphne E, Weckhuysen Bert M, Koningsberger Diek C
Inorganic Chemistry and Catalysis Group, Department of Chemistry, Utrecht University, 3508 TB Utrecht, The Netherlands.
Chemistry. 2007;13(20):5845-56. doi: 10.1002/chem.200601128.
The influence of changes in coordination number, interatomic distances, and oxidation state on the intensity and centroid position of the Fourier transform (FT) of the atomic X-ray absorption fine structure (AXAFS) peak of vanadium oxide bulk model compounds and alumina-supported vanadium oxide clusters has been investigated. Using Na3VO4 and V2O5 as model compounds, it has been shown that the nearest neighbour shells have a pronounced influence on the AXAFS intensity; specifically, a 40 % decrease in intensity was observed between these two compounds. Secondly, the influence of partial reduction of the vanadium oxide species has been determined; this led to a 50 % decrease in the AXAFS intensity and to an increase in the centroid position. Furthermore, the influence of the vanadium oxide loading has been assessed. A non-linear relationship between the vanadium oxide loading and the AXAFS intensity has been found, indicating that the AXAFS intensity is sensitive to the formation of V-O-V bridging bonds between the vanadium VO4 clusters. The results show that AXAFS can be used to probe the relative energy level of the vanadium valence orbitals.
研究了配位数、原子间距离和氧化态的变化对氧化钒体相模型化合物及氧化铝负载的氧化钒簇的原子X射线吸收精细结构（AXAFS）峰的傅里叶变换（FT）强度和质心位置的影响。以Na3VO4和V2O5作为模型化合物，结果表明最近邻壳层对AXAFS强度有显著影响；具体而言，在这两种化合物之间观察到强度降低了40%。其次，已确定了氧化钒物种部分还原的影响；这导致AXAFS强度降低了50%，且质心位置增加。此外，还评估了氧化钒负载量的影响。发现氧化钒负载量与AXAFS强度之间存在非线性关系，这表明AXAFS强度对钒VO4簇之间V-O-V桥键的形成敏感。结果表明，AXAFS可用于探测钒价轨道的相对能级。
