Coprecipitation of gold(III) complex ions with manganese(II) hydroxide and their stoichiometric reduction to atomic gold (Au(0)): Analysis by Mössbauer spectroscopy and XPS

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• 作者：Mamiko Yamashita ; Hironori Ohashi ; Yasuhiro Kobayashi ; Yoshihiro Okaue ; Tsutomu Kurisaki ; Hisanobu Wakita ; Takushi Yokoyama
• 关键词：Au(III) complex ion ; Coprecipitation ; Mn(OH)₂ ; Reduction ; Atomic Au ; Oxidation ; MnO₂ ; Environmental catalyst ; ¹⁹⁷Au Mö ; ssbauer spectra ; XPS
• 刊名：Journal of Colloid and Interface Science
• 出版年：2008
• 出版时间：1 March 2008
• 年：2008
• 卷：319
• 期：1
• 页码：25-29
• 全文大小：279 K

文摘

To elucidate the formation process of precursor of gold-supported manganese dioxide (MnO₂), the coprecipitation behavior of [AuCl_4−n(OH)_n]⁻ (n=0–4) (Au(III)) complex ions with manganese(II) hydroxide (Mn(OH)₂) and the change in their chemical state were examined. The Au(III) complex ions were rapidly and effectively coprecipitated with Mn(OH)₂ at pH 9. According to the Mössbauer spectra for gold (Au) coprecipitated with Mn(OH)₂, below an Au content of 60 wt % in the coprecipitates, all of the coprecipitated Au existed in the atomic state (Au(0)), while, above an Au content of 65 wt % , part of the gold existed in the Au(III) state, and the proportion increased with increasing coprecipitated Au content. Based on the results of X-ray photoelectron spectroscopy, Mn(II) in Mn(OH)₂ converted to Mn(IV) in conjunction with coprecipitation of Au(III) complex ions. These results indicate that the rapid stoichiometric reduction of Au(III) to Au(0) is caused by electron transfer from Mn(II) in Mn(OH)₂ to the Au(III) complex ion through an MnOAu bond.