High-Throughput Experimental Study of Wurtzite Mn 1- x Zn x O Alloys for Water Splitting Applications

Paul F. Ndione, Erin L Ratcliff, Suhash R. Dey, Emily L. Warren, Haowei Peng, Aaron M. Holder, Stephan Lany, Brian P. Gorman, Mowafak M. Al-Jassim, Todd G. Deutsch, Andriy Zakutayev, David S. Ginley

Research output: Contribution to journalArticle

Abstract

We used high-throughput experimental screening methods to unveil the physical and chemical properties of Mn 1-x Zn x O wurtzite alloys and identify their appropriate composition for effective water splitting application. The Mn 1-x Zn x O thin films were synthesized using combinatorial pulsed laser deposition, permitting for characterization of a wide range of compositions with x varying from 0 to 1. The solubility limit of ZnO in MnO was determined using the disappearing phase method from X-ray diffraction and X-ray fluorescence data and found to increase with decreasing substrate temperature due to kinetic limitations of the thin-film growth at relatively low temperature. Optical measurements indicate the strong reduction of the optical band gap down to 2.1 eV at x = 0.5 associated with the rock salt-to-wurtzite structural transition in Mn 1-x Zn x O alloys. Transmission electron microscopy results show evidence of a homogeneous wurtzite alloy system for a broad range of Mn 1-x Zn x O compositions above x = 0.4. The wurtzite Mn 1-x Zn x O samples with the 0.4 < x < 0.6 range were studied as anodes for photoelectrochemical water splitting, with a maximum current density of 340 μA cm -2 for 673 nm-thick films. These Mn 1-x Zn x O films were stable in pH = 10, showing no evidence of photocorrosion or degradation after 24 h under water oxidation conditions. Doping Mn 1-x Zn x O materials with Ga dramatically increases the electrical conductivity of Mn 1-x Zn x O up to ∼1.9 S/cm for x = 0.48, but these doped samples are not active in water splitting. Mott-Schottky and UPS/XPS measurements show that the presence of dopant atoms reduces the space charge region and increases the number of mid-gap surface states. Overall, this study demonstrates that Mn 1-x Zn x O alloys hold promise for photoelectrochemical water splitting, which could be enhanced with further tailoring of their electronic properties.

Original languageEnglish (US)
Pages (from-to)7436-7447
Number of pages12
JournalACS Omega
Volume4
Issue number4
DOIs
StatePublished - Apr 24 2019

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Throughput
Water
Chemical analysis
Doping (additives)
Thin films
Optical band gaps
Surface states
Film growth
Pulsed laser deposition
Electric space charge
Thick films
Electronic properties
Chemical properties
Screening
Anodes
Current density
X ray photoelectron spectroscopy
Solubility
Physical properties
Salts

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)

Cite this

High-Throughput Experimental Study of Wurtzite Mn 1- x Zn x O Alloys for Water Splitting Applications . / Ndione, Paul F.; Ratcliff, Erin L; Dey, Suhash R.; Warren, Emily L.; Peng, Haowei; Holder, Aaron M.; Lany, Stephan; Gorman, Brian P.; Al-Jassim, Mowafak M.; Deutsch, Todd G.; Zakutayev, Andriy; Ginley, David S.

In: ACS Omega, Vol. 4, No. 4, 24.04.2019, p. 7436-7447.

Research output: Contribution to journalArticle

Ndione, PF, Ratcliff, EL, Dey, SR, Warren, EL, Peng, H, Holder, AM, Lany, S, Gorman, BP, Al-Jassim, MM, Deutsch, TG, Zakutayev, A & Ginley, DS 2019, ' High-Throughput Experimental Study of Wurtzite Mn 1- x Zn x O Alloys for Water Splitting Applications ', ACS Omega, vol. 4, no. 4, pp. 7436-7447. https://doi.org/10.1021/acsomega.8b03347
Ndione, Paul F. ; Ratcliff, Erin L ; Dey, Suhash R. ; Warren, Emily L. ; Peng, Haowei ; Holder, Aaron M. ; Lany, Stephan ; Gorman, Brian P. ; Al-Jassim, Mowafak M. ; Deutsch, Todd G. ; Zakutayev, Andriy ; Ginley, David S. / High-Throughput Experimental Study of Wurtzite Mn 1- x Zn x O Alloys for Water Splitting Applications In: ACS Omega. 2019 ; Vol. 4, No. 4. pp. 7436-7447.
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AU - Warren, Emily L.

AU - Peng, Haowei

AU - Holder, Aaron M.

AU - Lany, Stephan

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