Enhancement of Charge Separation and Hydrogen Evolution on Particulate La5Ti2CuS5O7 Photocathodes by Surface Modification

Jingyuan Liu; Takashi Hisatomi; Dharmapura H K Murthy; Miao Zhong; Mamiko Nakabayashi; Tomohiro Higashi; Yohichi Suzuki; Hiroyuki Matsuzaki; Kazuhiko Seki; Akihiro Furube; Naoya Shibata; Masao Katayama; Tsutomu Minegishi; Kazunari Domen

doi:10.1021/acs.jpclett.6b02735

Enhancement of Charge Separation and Hydrogen Evolution on Particulate La₅Ti₂CuS₅O₇ Photocathodes by Surface Modification

J Phys Chem Lett. 2017 Jan 19;8(2):375-379. doi: 10.1021/acs.jpclett.6b02735. Epub 2017 Jan 4.

Authors

Jingyuan Liu¹, Takashi Hisatomi^{1

2}, Dharmapura H K Murthy³, Miao Zhong^{1

2}, Mamiko Nakabayashi⁴, Tomohiro Higashi^{1

2}, Yohichi Suzuki³, Hiroyuki Matsuzaki³, Kazuhiko Seki³, Akihiro Furube^{3

5}, Naoya Shibata⁴, Masao Katayama^{1

2}, Tsutomu Minegishi^{1

2

6}, Kazunari Domen^{1

2}

Affiliations

¹ Department of Chemical System Engineering, School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, 113-8656 Tokyo, Japan.
² Japan Technological Research Association of Artificial Photosynthetic Chemical Process (ARPChem) , 2-11-9 Iwamotocho, Chiyoda-ku, 101-0032 Tokyo, Japan.
³ National Institute of Advanced Industrial Science and Technology , Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, 305-8568 Ibaraki, Japan.
⁴ Institute of Engineering Innovation, School of Engineering, The University of Tokyo , 2-11-16 Yayoi, Bunkyo-ku, 113-8656 Tokyo, Japan.
⁵ Department of Optical Science, Tokushima University , 2-1 Minamijosanjima-cho, 770-8506 Tokushima, Japan.
⁶ Japan Science and Technology Agency/Precursory Research for Embryonic Science and Technology (JST/PRESTO) , Kawaguchi Center Building, 4-1-8 Honcho, Kawaguchi-shi, 332-0012 Saitama, Japan.

PMID: 28033010
DOI: 10.1021/acs.jpclett.6b02735

Abstract

Particulate La₅Ti₂CuS₅O₇ (LTC) photocathodes prepared by particle transfer show a positive onset potential of 0.9 V vs RHE for the photocathodic current in photoelectrochemical (PEC) H₂ evolution. However, the low photocathodic current imposes a ceiling on the solar-to-hydrogen energy conversion efficiency of PEC cells based on LTC photocathodes. To improve the photocurrent, in this work, the surface of Mg-doped LTC photocathodes was modified with TiO₂, Nb₂O₅, and Ta₂O₅ by radio frequency reactive magnetron sputtering. The photocurrent of the modified Mg-doped LTC photocathodes was doubled because these oxides formed type-II heterojunctions and extended the lifetimes of photogenerated charge carriers. The enhanced photocathodic current was attributed to hydrogen evolution at a positive potential of +0.7 V vs RHE. This work opens up possibilities for improving PEC hydrogen evolution on particulate photocathodes based on surface oxide modifications and also highlights the importance of the band gap alignment.