Operando Investigation of Mn3O4+δ Co-catalyst on Fe2O3 Photoanode: Manganese-Valency-Determined Enhancement at Varied Potentials

Ying Liu; Chao Wei; Chee Keong Ngaw; Ye Zhou; Shengnan Sun; Shibo Xi; Yonghua Du; Joachim S.C. Loo; Joel W. Ager; Zhichuan J. Xu

doi:10.1021/acsaem.7b00267

Operando Investigation of Mn₃O_4+δ Co-catalyst on Fe₂O₃ Photoanode: Manganese-Valency-Determined Enhancement at Varied Potentials

Ying Liu, Chao Wei, Chee Keong Ngaw, Ye Zhou, Shengnan Sun, Shibo Xi, Yonghua Du, Joachim S.C. Loo^*, Joel W. Ager, Zhichuan J. Xu

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

24 Citations (Scopus)

Abstract

The development of efficient catalysts containing earth-abundant elements for the oxygen evolution reaction (OER) in photoelectrochemical (PEC) systems is highly desired for low-cost energy storage and conversion. In this work, mesoporous α-Fe₂O₃ thin film photoanodes coated with manganese oxide (Mn₃O_4+δ) co-catalysts are prepared by a dip-coating method. The co-catalyst coating significantly enhances PEC water oxidation performance as compared with the uncoated α-Fe₂O₃. To understand the origin of this enhancement, in situ X-ray absorption spectroscopy is employed to monitor the valence state of Mn in the Mn₃O_4+δ co-catalyst as a function of applied potential. It is found that the enhancement of the photocurrent is governed by the Mn valency, and the most prominent enhancement takes place at the valency of ∼3.4+, which is due to the optimal e_g electron filling in Mn cations as the electrocatalyst for OER. Our investigation indicates that the contribution of Mn₃O_4+δ co-catalyst to OER kinetics is variable at different applied potentials.

Original language	English
Pages (from-to)	814-821
Number of pages	8
Journal	ACS Applied Energy Materials
Volume	1
Issue number	2
DOIs	https://doi.org/10.1021/acsaem.7b00267
Publication status	Published - Feb 26 2018
Externally published	Yes

Bibliographical note

Publisher Copyright:
© 2018 American Chemical Society.

ASJC Scopus Subject Areas

Chemical Engineering (miscellaneous)
Energy Engineering and Power Technology
Electrochemistry
Materials Chemistry
Electrical and Electronic Engineering

Keywords

co-catalyst
hematite
manganese oxide
photoanode
valency

Access to Document

10.1021/acsaem.7b00267

Cite this

@article{eadfbf129eda46e88bcf4233e7c85177,

title = "Operando Investigation of Mn3O4+δ Co-catalyst on Fe2O3 Photoanode: Manganese-Valency-Determined Enhancement at Varied Potentials",

abstract = "The development of efficient catalysts containing earth-abundant elements for the oxygen evolution reaction (OER) in photoelectrochemical (PEC) systems is highly desired for low-cost energy storage and conversion. In this work, mesoporous α-Fe2O3 thin film photoanodes coated with manganese oxide (Mn3O4+δ) co-catalysts are prepared by a dip-coating method. The co-catalyst coating significantly enhances PEC water oxidation performance as compared with the uncoated α-Fe2O3. To understand the origin of this enhancement, in situ X-ray absorption spectroscopy is employed to monitor the valence state of Mn in the Mn3O4+δ co-catalyst as a function of applied potential. It is found that the enhancement of the photocurrent is governed by the Mn valency, and the most prominent enhancement takes place at the valency of ∼3.4+, which is due to the optimal eg electron filling in Mn cations as the electrocatalyst for OER. Our investigation indicates that the contribution of Mn3O4+δ co-catalyst to OER kinetics is variable at different applied potentials.",

keywords = "co-catalyst, hematite, manganese oxide, photoanode, valency",

author = "Ying Liu and Chao Wei and Ngaw, {Chee Keong} and Ye Zhou and Shengnan Sun and Shibo Xi and Yonghua Du and Loo, {Joachim S.C.} and Ager, {Joel W.} and Xu, {Zhichuan J.}",

note = "Publisher Copyright: {\textcopyright} 2018 American Chemical Society.",

year = "2018",

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doi = "10.1021/acsaem.7b00267",

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T1 - Operando Investigation of Mn3O4+δ Co-catalyst on Fe2O3 Photoanode

T2 - Manganese-Valency-Determined Enhancement at Varied Potentials

AU - Liu, Ying

AU - Wei, Chao

AU - Ngaw, Chee Keong

AU - Zhou, Ye

AU - Sun, Shengnan

AU - Xi, Shibo

AU - Du, Yonghua

AU - Loo, Joachim S.C.

AU - Ager, Joel W.

AU - Xu, Zhichuan J.

PY - 2018/2/26

Y1 - 2018/2/26

N2 - The development of efficient catalysts containing earth-abundant elements for the oxygen evolution reaction (OER) in photoelectrochemical (PEC) systems is highly desired for low-cost energy storage and conversion. In this work, mesoporous α-Fe2O3 thin film photoanodes coated with manganese oxide (Mn3O4+δ) co-catalysts are prepared by a dip-coating method. The co-catalyst coating significantly enhances PEC water oxidation performance as compared with the uncoated α-Fe2O3. To understand the origin of this enhancement, in situ X-ray absorption spectroscopy is employed to monitor the valence state of Mn in the Mn3O4+δ co-catalyst as a function of applied potential. It is found that the enhancement of the photocurrent is governed by the Mn valency, and the most prominent enhancement takes place at the valency of ∼3.4+, which is due to the optimal eg electron filling in Mn cations as the electrocatalyst for OER. Our investigation indicates that the contribution of Mn3O4+δ co-catalyst to OER kinetics is variable at different applied potentials.

AB - The development of efficient catalysts containing earth-abundant elements for the oxygen evolution reaction (OER) in photoelectrochemical (PEC) systems is highly desired for low-cost energy storage and conversion. In this work, mesoporous α-Fe2O3 thin film photoanodes coated with manganese oxide (Mn3O4+δ) co-catalysts are prepared by a dip-coating method. The co-catalyst coating significantly enhances PEC water oxidation performance as compared with the uncoated α-Fe2O3. To understand the origin of this enhancement, in situ X-ray absorption spectroscopy is employed to monitor the valence state of Mn in the Mn3O4+δ co-catalyst as a function of applied potential. It is found that the enhancement of the photocurrent is governed by the Mn valency, and the most prominent enhancement takes place at the valency of ∼3.4+, which is due to the optimal eg electron filling in Mn cations as the electrocatalyst for OER. Our investigation indicates that the contribution of Mn3O4+δ co-catalyst to OER kinetics is variable at different applied potentials.

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