Photon Factory Activity Report 2014 #32 (2015) B

AR-NW10A/2013G159

Site Structure of BiO1–xCl1–y Photocathode in Photofuel Cell that Uses Acidic Water asa Fuel
Mao Yoshiba, Yuta Ogura, and Yasuo Izumi*
Graduate School of Science, Chiba University, Yayoi, 1-33, Inage-ku, Chiba 263-8522
In-situ site structure of photocathode comprising bismuth compound in photofuel cell was successfully clarified using Bi
L3-edge EXAFS.
1 Introduction
The ex-situ structure of photocathode bismuth
oxychloride (BiOCl) in photofuel cell was reported inPhoton Factory Activity Report 2013 [1]. The photofuel
cell in this study is very unique that uses acidic water as afuel [2]. Herein, the structure of BiOCl was studied underin-situ condition of photofuel cell [3].
2 Experimental Section
BiOCl was synthesized via the solvothermal procedurereported in reference 3. A BiOCl flim was set in the HClsolution (pH 2.0) for cathode of a photofuel cell [2, 3]
equipped with polyethylene naphthalate (Q51-16, TeijiDupont) window for X-ray beam and UV–visible lightirradiations.
Bismuth L3-edge EXAFS spectra were obtained at 290
K in the transmission mode. On the beamline, the BiOCl
photoelectrode film was irradiated by UV–visible lightfor 60 min. The behavior of the Bi sites was monitored
also after the light was off.
3 Results and Discussion
The BiOCl film immersed in HCl aqueous solution (pH2.0) irradiated by UV-visible light was analyzed (Table1a). The color of the film was light gray. The
coordination number (N) of both Bi–O and Bi–Cl
decreased from 4.0 to 2.2 and from 4.0 to 3.1,
respectively. Taken the fit errors into account, the oxygenvacancy could be formed.
Table 1: The curve-fit analysis result of Bi L3-edge
EXAFS for BiOCl
Bi-O

Sample(a)
In HCl (pH 2.0), O2
gas, & UV–visible,35 min(b)
Sample a, 12 minafter UV–visible
was off

Bi-Cl
R (nm)NΔσ 2 (10–5 nm2)
0.250
0.329
(±0.001) (±0.012)
2.2
3.1(±0.2)(±0.7)
1.4
2.2(±0.5)(±1.7)
0.247
0.331(±0.001) (±0.012)
4.2
4.6(±0.6)(±1.9)
6.0
5.7(±1.4)(±1.8)

Goodness of fit

Then, UV-visible light was turned off. A Bi L3-edge
EXAFS spectrum was obtained at 12 min in the dark. The
shape of EXAFS oscillation was similar to that for thesample irradiated by UV-visible light, but the reduced
amplitude in the whole spectrum region irradiated bylight seemed to recover to the level for the as-synthesized
fresh BiOCl sample. In fact, the N(Bi–O) and N(Bi–Cl)
values recovered to 4.2 and 4.6 (Table 1b), respectively,
similar to that for as-synthesized BiOCl (4.0) [1, 3]. Thus,
the O and Cl vacancy formed in HCl aqueous solution
irradiated by UV–visible light is suggested to betransformed to the original BiOCl crystalline state soonafter the light was turned off.
Acknowledgements
The authors are grateful for financial support from theFeasibility Study Stage of A-STEP (AS251Z00906L,AS231Z01459C) from the Japan Science and Technology
Agency, the Iwatani Naoji Foundation (2011–2012), anda Grant-in-Aid for Scientific Research C (26410204,22550117) from the Japan Society for the Promotion ofScience.
References[1] Y. Fujishima, S. Okamoto, M. Yoshiba, Y. Ogura, andY. Izumi, Photon Factory Activity Report 2013 31B,
2013G159 (2014).
[2] Y. Ogura, S. Okamoto, T. Itoi, Y. Fujishima, Y.
Yoshida, and Y. Izumi, Chemical Communications 50,3067–3070 (2014).
[3] Y. Fujishima, S. Okamoto, M. Yoshiba, T. Itoi, S.
Kawamura, Y.Yoshida, Y. Ogura, and Y. Izumi,
Journal of Materials Chemistry A 3, 8389–8404(2015).

1.4 × 105

Research Achievements(1) 出願番号：特願2014–242685
発明者：泉 康雄、小倉優太
発明の名称：燃料電池
出願人：千葉大学
出願日：2014年11月30日

3.2 × 105(2) 出願番号：特願2013–211926
発明者：泉 康雄、小倉優太、藤嶋幸子
発明の名称：燃料電池

Photon Factory Activity Report 2014 #32 (2015) B

出願人：千葉大学
出願日：2013年10月9日
優先権：特願2012–223765, 特願2012–254796
優先日：2012年10月9日(3) 出願番号：特願2012–254796
発明者：泉 康雄、小倉優太
発明の名称：燃料電池
出願人：千葉大学
出願日：2012年11月21日
優先権：特願2012–223765
優先日：2012年10月9日(4) 出願番号：特願2012–223765
発明者：泉 康雄、小倉優太
発明の名称：燃料電池
出願人：千葉大学
出願日：2012年10月9日* yizumi@faculty.chiba-u.jp

AR-NW10A/2013G159