Examination of the proposition that Cu(II) can be required for charge neutrality in a sulfide lattice - Cu in tetrahedrites and sphalerite
Examination of the proposition that Cu(II) can be required for charge neutrality in a sulfide lattice - Cu in tetrahedrites and sphalerite
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DOI：
10.1139/v07-078
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发表时间：
2007-10-01
影响因子：
1.1
通讯作者：
Yang, Yaw-wen
中科院分区：
文献类型：
--
作者：
Buckley, Alan N.;Skinner, William M.;Yang, Yaw-wen
用同步辐射XPS和Cu L-2，L-3边NEXAFS谱对一个天然黝铜矿表面进行了研究，结果与矿物成分及其预期的半导电性符合雅阁。6配位S原子的2 p结合能并不明显大于4配位S原子的2 p结合能，表面物种在表面优化的S 2 p或Cu 2 p光谱中也不能清楚地分辨。Cu 2 p和Cu L-2、L-3边光谱表明，矿物中的Cu均为Cu（I）。用弱酸性铜水溶液处理的相对纯的天然闪锌矿的Cu L-2，L-3边光谱显示Cu（II）存在于断裂表面的最外层，但可以得出结论，矿物表面附近的大部分Cu处于形式氧化态Cu（I），尽管具有高于正常d（9）的特征。Cu（I）吸收峰的能量远低于黝铜矿吸收边的能量，但仍与S的4倍配位Cu（I）一致。的Cu（II）是一致的与铜键合到闪锌矿的最外层中的S原子和化学吸附水中的O原子。在不同的光子能量下确定的S-2 p光谱揭示了高结合能的成分所产生的低聚硫化物样的环境中的最外层，但不一定在一个完全重构的晶格，而不是在一个铜低聚硫化物。数据表明，除了在硫化物晶格的最外层中被Cu取代的Zn之外，Zn也有一些损失。这些低聚硫化物样的环境的存在下，排除了检测的正式氧化态大于（-II），可能只出现在S晶格中的Cu（I）的S。没有证据表明在硫化物晶格中存在Cu（II），但不能排除浓度非常低的可能性，因为在经处理的闪锌矿表面存在与S和O键合的Cu（II）。
Synchrotron XPS and Cu L-2,L-3-edge NEXAFS spectroscopic data for a natural tetrahedrite surface prepared by fracture under UHV were in accord with the composition of the mineral and its expected semi conductivity. The 2p binding energy for the 6-coordinate S atoms was found to be not delectably greater than that for the 4-coordinate S atoms, and surface species were not clearly discernible in either surface-optimized S 2p Or Cu 2p spectra. The Cu 2p and Cu L-2,L-3-edge spectra indicated that all Cu in the mineral was indisputably Cu(I). The Cu L-2,L-3-edge spectra of relatively pure natural sphalerite treated with mildly acidic aqueous cupric solution revealed the presence of Cu(II) in the outermost layer of the fracture surfaces, but it was concluded that most of the Cu near the surface of the mineral was in formal oxidation state Cu(I), albeit with higher than normal d(9) character. The Cu(I) absorption peak was at an energy much lower than for the tetrahedrite absorption edge, but still consistent with Cu(I) in 4-fold coordination by S. The Cu(II) was consistent with Cu bonded both to S atoms in the outermost layer of the sphalerite and to O atoms in chemisorbed water. S 2p spectra determined at different photon energies revealed high binding energy components arising from oligosulfide-like environments in the outermost layers, but not necessarily in a completely restructured lattice and not in a Cu oligosulfide only. The data indicated some loss of Zn in addition to the Zn that had been replaced by Cu in the outermost layers of the sulfide lattice. The presence of these oligosulfide-like environments precluded the detection of S with formal oxidation state greater than (-II) that might have arisen only from Cu(I) in the S lattice. No evidence was obtained for the presence of Cu(II) in a sulfide lattice, but it was not possible to exclude the possibility of a very low concentration because of the presence of the Cu(II) bonded to both S and O at the surface of the treated sphalerite.