IN-SITU X-RAY-ABSORPTION FINE-STRUCTURE STUDIES OF FOREIGN METAL-IONS IN NICKEL HYDROUS OXIDE ELECTRODES IN ALKALINE ELECTROLYTES
IN-SITU X-RAY-ABSORPTION FINE-STRUCTURE STUDIES OF FOREIGN METAL-IONS IN NICKEL HYDROUS OXIDE ELECTRODES IN ALKALINE ELECTROLYTES
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DOI：
10.1021/j100091a049
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发表时间：
1994-10-06
影响因子：
--
通讯作者：
SCHERSON, D
中科院分区：
文献类型：
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作者：
KIM, SH;TRYK, DA;SCHERSON, D
用原位X射线吸收精细结构（XAFS）研究了在碱性电解液中电沉积Ni和（9：1）Ni/Co、（9：1）Ni/Fe复合氧化物膜的结构和电子性质。对这些复合水合氧化物的Co和Fe K边的X射线吸收近边结构（XANES）和扩展X射线吸收精细结构（EXAFS）的分析表明，无论膜中镍位点的氧化态如何，客体金属离子以Co 3+和Fe 3+存在，钴-氧距离d（Co-O）= 1.90 +/-0.02埃，d（Fe-O）= 1.92 +/-0.02埃。后者的值是在良好的协议与d（Me-O）（Me = Co或Fe）在CoOOH和β-和γ-FeOOH，分别由常规的X-射线衍射测定。两个明确定义的Me-Ni第一配位壳层可以观察到在一个潜在的Ni 2+和Ni 3+的网站，预计将存在的客体金属的K-边EXAFS的傅立叶变换（FT）。这些FT特征的相对强度可以通过改变所施加的电势或等效地通过改变两个镍位点的相对群体来改变。在此基础上，将Me-Ni壳层归属于邻近Ni ~（2+）和Ni ~（3+）位的Co ~（3+）。此外，d（Ni-Co）和d（Ni-Fe）对于一个给定的镍氧化态被发现是基本上相同的观察到的d（Ni-Ni）在纯镍水合氧化物膜。这提供了Co 3+和Fe 3+离子取代水合氧化物晶格中的Ni位点，形成单相材料的证据。
Aspects of the structural and electronic properties of hydrous oxide films of Ni and of composite (9:1) Ni/Co and (9:1) Ni/Fe, prepared by electrodeposition, have been examined in alkaline electrolytes using in situ X-ray absorption fine structure (XAFS). An analysis of the X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) for the Co and Fe K-edges of these composite hydrous oxides revealed that, regardless of the oxidation state of nickel sites in the films, the guest metal ions are present as Co3+ and Fe3+ and that the cobalt-oxygen distance d(Co-O) = 1.90 +/- 0.02 Angstrom and d(Fe-O) = 1.92 +/- 0.02 Angstrom. The latter values are in excellent agreement with d(Me-O) (Me = Co or Fe) in CoOOH and beta- and gamma-FeOOH, respectively, determined by conventional X-ray diffraction. Two clearly defined Me-Ni first coordination shells could be observed in the Fourier transforms (FT) of the K-edge EXAFS of the guest metal recorded at a potential at which both Ni2+ and Ni3+ sites are expected to be present. The relative intensities of these FT features could be varied by changing the applied potential or, equivalently, the relative population of the two nickel sites. On the basis of these results, the Me-Ni shells are ascribed to Co3+ adjacent to Ni2+ and Ni3+ sites. Furthermore, d(Ni-Co) and d(Ni-Fe) for a given nickel oxidation state are found to be essentially the same as those observed for d(Ni-Ni) in pure nickel hydrous oxide films. This provides evidence that Co3+ and Fe3+ ions replace Ni sites in the hydrous oxide lattice, forming single-phase materials.