In situ IR spectroscopy during oxidation process of cobalt Prussian blue analogues

Hideharu Niwa; Toshiaki Moriya; Takayuki Shibata; Yuya Fukuzumi; Yutaka Moritomo

doi:10.1038/s41598-021-83699-8

In situ IR spectroscopy during oxidation process of cobalt Prussian blue analogues

Sci Rep. 2021 Feb 18;11(1):4119. doi: 10.1038/s41598-021-83699-8.

Authors

Hideharu Niwa^{1

2

3}, Toshiaki Moriya⁴, Takayuki Shibata⁵, Yuya Fukuzumi⁴, Yutaka Moritomo^{6

7

8}

Affiliations

¹ Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, 305-8571, Japan. niwa.hideharu.ga@u.tsukuba.ac.jp.
² Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, 305-8571, Japan. niwa.hideharu.ga@u.tsukuba.ac.jp.
³ Tsukuba Research Center for Energy Materials Science (TREMS), University of Tsukuba, Tsukuba, 305-8571, Japan. niwa.hideharu.ga@u.tsukuba.ac.jp.
⁴ Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, 305-8571, Japan.
⁵ National Institute of Technology, Gunma College, Maebashi, Gunma, 371-8530, Japan.
⁶ Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, 305-8571, Japan. moritomo.yutaka.gf@u.tsukuba.ac.jp.
⁷ Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, 305-8571, Japan. moritomo.yutaka.gf@u.tsukuba.ac.jp.
⁸ Tsukuba Research Center for Energy Materials Science (TREMS), University of Tsukuba, Tsukuba, 305-8571, Japan. moritomo.yutaka.gf@u.tsukuba.ac.jp.

Abstract

Cobalt Prussian blue analogues (Co-PBA; Na_xCo[Fe(CN)₆]_y), consisting of cyano-bridged transition metal network, -Fe-CN-Co-NC-Fe-, are promising cathode materials for Na-ion secondary batteries. In the oxidation process, oxidization of Fe and/or Co are compensated by Na⁺ deintercalation. Here, we investigated the oxidization process of three Co-PBAs by means of in situ infrared absorption (IR) spectroscopy. With use of an empirical rule of the frequencies of the CN^- stretching mode in ferrocyanide ([Fe^II(CN)₆]^4-) and ferricyanide ([Fe^III(CN)₆]^3-), the oxidation processes of Co-PBAs were determined against the Fe concentration (y) and temperature (T). We will discuss the interrelation between the oxidation processes and Fe concentration (y).

Grants and funding

JP17H0113/JSPS KAKENHI