High-Throughput Experimental Study of Wurtzite Mn1–xZnxO Alloys for Water Splitting Applications
AuthorNdione, Paul F.
Ratcliff, Erin L.
Dey, Suhash R.
Warren, Emily L.
Holder, Aaron M.
Gorman, Brian P.
Al-Jassim, Mowafak M.
Deutsch, Todd G.
Ginley, David S.
AffiliationUniv Arizona, Dept Mat Sci & Engn
MetadataShow full item record
PublisherAMER CHEMICAL SOC
CitationACS Omega 2019 4 (4), 7436-7447 DOI: 10.1021/acsomega.8b03347
RightsCopyright © 2019 American Chemical Society. This is an open access article published under an ACS Author Choice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes.
Collection InformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at firstname.lastname@example.org.
AbstractWe used high-throughput experimental screening methods to unveil the physical and chemical properties of Mn1-xZnxO wurtzite alloys and identify their appropriate composition for effective water splitting application. The Mn1-xZnxO 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 Mn1-xZnxO 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 Mn1-xZnxO alloys. Transmission electron microscopy results show evidence of a homogeneous wurtzite alloy system for a broad range of Mn1-xZnxO compositions above x = 0.4. The wurtzite Mn1-xZnxO samples with the 0.4 < x < 0.6 range were studied as anodes for photoelectrochemical water splitting, with a maximum current density of 340 mu A cm(-2) for 673 nm-thick films. These Mn1-xZnxO films were stable in pH = 10, showing no evidence of photocorrosion or degradation after 24 h under water oxidation conditions. Doping Mn1-xZnxO materials with Ga dramatically increases the electrical conductivity of Mn1-xZnxO up to similar 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 midgap surface states. Overall, this study demonstrates that Mn1-xZnxO alloys hold promise for photoelectrochemical water splitting, which could be enhanced with further tailoring of their electronic properties.
NoteOpen access journal
VersionFinal published version
SponsorsU.S. Department of Energy (DOE) [DE-AC36-08GO28308]; Office of Science; Office of Basic Energy Sciences (BES), Energy Frontier Research Center "Center for Next Generation of Materials Design: Incorporating Metastability"; Indo-US Science and Technology Forum [BASE 2014/F-8]