Homogeneous Electron Doping into Nonstoichiometric Strontium Titanate Improves Its Photocatalytic Activity for Hydrogen and Oxygen Evolution

Shunta Nishioka, Junji Hyodo, Junie Jhon M. Vequizo, Shunsuke Yamashita, Hiromu Kumagai, Koji Kimoto, Akira Yamakata, Yoshihiro Yamazaki, Kazuhiko Maeda

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Water splitting using a semiconductor photocatalyst has been extensively studied as a means of solar-to-hydrogen energy conversion. Powder-based semiconductor photocatalysts, in particular, have tremendous potential in cost mitigation due to system simplicity and scalability. The control and implementation of powder-based photocatalysts are, in reality, quite complex. The identification of the semiconductor-photocatalytic activity relationship and its limiting factor has not been fully solved in any powder-based semiconductor photocatalyst. In this work, we present systematic and quantitative evaluation of photocatalytic hydrogen and oxygen evolution using a model strontium titanate powder/aqueous solution interface in a half reaction. The electron density was controlled from 1016 to 1020 cm-3 throughout the strontium titanate powder by charge compensation with oxygen nonstoichiometry (the amount of oxygen vacancy) while maintaining its crystallinity, chemical composition, powder morphology, and the crystal and electronic structure of the surface. The photocatalytic activity of hydrogen evolution from aqueous methanol solution was stable and enhanced by 40-fold by the electron doping. The enhancement was correlated well with increased Δabsorbance, an indication of prolonged lifetime of photoexcited electrons, observed by transient absorption spectroscopy. Photocatalytic activity of oxygen evolution from aqueous silver nitrate solution was also enhanced by 3-fold by the electron doping. Linear correlation was found between the photocatalytic activity and the degree of surface band bending, ΔΦ, above 1.38 V. The band bending, potential downhill for electronic holes, enlarges the total flux of photoexcited holes toward the surface, which drives the oxygen evolution reaction.

Original languageEnglish
Pages (from-to)7190-7200
Number of pages11
JournalACS Catalysis
Volume8
Issue number8
DOIs
Publication statusPublished - Aug 3 2018

Fingerprint

Strontium
Powders
Hydrogen
Doping (additives)
Photocatalysts
Oxygen
Electrons
Semiconductor materials
Silver Nitrate
Oxygen vacancies
Absorption spectroscopy
Energy conversion
Electronic structure
Carrier concentration
Methanol
strontium titanium oxide
Scalability
Nitrates
Silver
Crystal structure

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)

Cite this

Homogeneous Electron Doping into Nonstoichiometric Strontium Titanate Improves Its Photocatalytic Activity for Hydrogen and Oxygen Evolution. / Nishioka, Shunta; Hyodo, Junji; Vequizo, Junie Jhon M.; Yamashita, Shunsuke; Kumagai, Hiromu; Kimoto, Koji; Yamakata, Akira; Yamazaki, Yoshihiro; Maeda, Kazuhiko.

In: ACS Catalysis, Vol. 8, No. 8, 03.08.2018, p. 7190-7200.

Research output: Contribution to journalArticle

Nishioka, S, Hyodo, J, Vequizo, JJM, Yamashita, S, Kumagai, H, Kimoto, K, Yamakata, A, Yamazaki, Y & Maeda, K 2018, 'Homogeneous Electron Doping into Nonstoichiometric Strontium Titanate Improves Its Photocatalytic Activity for Hydrogen and Oxygen Evolution', ACS Catalysis, vol. 8, no. 8, pp. 7190-7200. https://doi.org/10.1021/acscatal.8b01379
Nishioka, Shunta ; Hyodo, Junji ; Vequizo, Junie Jhon M. ; Yamashita, Shunsuke ; Kumagai, Hiromu ; Kimoto, Koji ; Yamakata, Akira ; Yamazaki, Yoshihiro ; Maeda, Kazuhiko. / Homogeneous Electron Doping into Nonstoichiometric Strontium Titanate Improves Its Photocatalytic Activity for Hydrogen and Oxygen Evolution. In: ACS Catalysis. 2018 ; Vol. 8, No. 8. pp. 7190-7200.
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