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

Mamiko Yamashita; Hironori Ohashi; Yasuhiro Kobayashi; Yoshihiro Okaue; Tsutomu Kurisaki; Hisanobu Wakita; Takushi Yokoyama

doi:10.1016/j.jcis.2007.10.034

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

J Colloid Interface Sci. 2008 Mar 1;319(1):25-9. doi: 10.1016/j.jcis.2007.10.034. Epub 2007 Dec 11.

Authors

Mamiko Yamashita¹, Hironori Ohashi, Yasuhiro Kobayashi, Yoshihiro Okaue, Tsutomu Kurisaki, Hisanobu Wakita, Takushi Yokoyama

Affiliation

¹ Department of Chemistry, Faculty of Science, Kyushu University, Ropponmatsu, Chuo-ku, Fukuoka 810-8560, Japan.

PMID: 18067911
DOI: 10.1016/j.jcis.2007.10.034

Abstract

To elucidate the formation process of precursor of gold-supported manganese dioxide (MnO2), the coprecipitation behavior of [AuCl4-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 Mn-O-Au bond.