Synthesis of ε-Keggin-Type Cobaltomolybdate-Based 3D Framework Material and Characterization Using Atomic-Scale HAADF-STEM and XANES

Takumi Igarashi; Zhenxin Zhang; Terufumi Haioka; Nao Iseki; Norihito Hiyoshi; Norihito Sakaguchi; Chisato Kato; Sadafumi Nishihara; Katsuya Inoue; Akira Yamamoto; Hisao Yoshida; Nao Tsunoji; Wataru Ueda; Tsuneji Sano; Masahiro Sadakane

doi:10.1021/acs.inorgchem.6b02748

Synthesis of ε-Keggin-Type Cobaltomolybdate-Based 3D Framework Material and Characterization Using Atomic-Scale HAADF-STEM and XANES

Inorg Chem. 2017 Feb 20;56(4):2042-2049. doi: 10.1021/acs.inorgchem.6b02748. Epub 2017 Feb 9.

Authors

Takumi Igarashi¹, Zhenxin Zhang², Terufumi Haioka¹, Nao Iseki¹, Norihito Hiyoshi³, Norihito Sakaguchi⁴, Chisato Kato⁵, Sadafumi Nishihara^{5

6}, Katsuya Inoue^{5

6}, Akira Yamamoto^{7

8}, Hisao Yoshida^{7

8}, Nao Tsunoji¹, Wataru Ueda², Tsuneji Sano¹, Masahiro Sadakane^{1

9}

Affiliations

¹ Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University , 1-4-1 Kagamiyama, Higashi Hiroshima 739-8527, Japan.
² Faculty of Engineering, Kanagawa University , Rokkakubashi, Kanagawa-ku, Yokohama-shi, Kanagawa 221-8686, Japan.
³ Research Institute for Chemical Process Technology, National Institute of Advanced Industrial Science and Technology (AIST) , 4-2-1 Nigatake, Miyagino, Sendai 983-8551, Japan.
⁴ Faculty of Engineering, Hokkaido University , N-13, W-8, Sapporo 060-8626, Japan.
⁵ Graduate School of Science & Center for Chiral Science, Hiroshima University , 1-3-1. Kagamiyama, 732-8526, Higashi-Hiroshima, Japan.
⁶ Institute for Advanced Materials Research, Hiroshima University & Natural Science Center for Basic Research and Development , 1-3-1, Kagamiyama, Higashi Hiroshima, Hiroshima 739-8526, Japan.
⁷ Graduate School of Human and Environmental Studies, Kyoto University , Yoshida-nihonmatsu-cho, Sakyo-ku, Kyoto 606-8501, Japan.
⁸ Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University , Kyotodaigaku Katsura, Nishikyo, Kyoto 615-8520, Japan.
⁹ JST, PRESTO , 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.

PMID: 28182416
DOI: 10.1021/acs.inorgchem.6b02748

Abstract

We describe the preparation of ε-Keggin-type cobaltomolybdate-based 3D frameworks with sodium cations, NaH₉[ε-Co^IIMo^V₈Mo^VI₄O₄₀Co^II₂], and their characterization by high-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure (XAFS) spectroscopy. Atomic-scale HAADF-STEM images of ε-Keggin compounds were obtained for the first time, and positions of Mo and Co were confirmed. Furthermore, clear evidence of the presence of a CoO₄ tetrahedron was obtained by X-ray absorption near-edge structure (XANES) analysis. Their characterization clearly revealed that ε-Keggin-type cobaltomolybdate units, [ε-CoMo₁₂O₄₀]^n-, constructed by a central Co^IIO₄ tetrahedron and 12 surrounding MoO₆ octahedra, are linked with Co^II to form 3D frameworks.