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Title: Identification of Copper(II)-Lactate Complexes in Cu₂O Electrodeposition Baths: Deprotonation of the alpha-Hydroxyl Group in Highly Concentrated Alkaline Solution
Authors: Chen, Tianyu
Kitada, Atsushi  kyouindb  KAKEN_id  orcid (unconfirmed)
Seki, Yusuke
Fukami, Kazuhiro  kyouindb  KAKEN_id  orcid (unconfirmed)
Usmanov, Dilshadbek T.
Chen, Lee Chuin
Hiraoka, Kenzo
Murase, Kuniaki  kyouindb  KAKEN_id  orcid (unconfirmed)
Author's alias: 陳, 天羽
北田 , 敦
関, 勇佑
深見, 一弘
邑瀬, 邦明
Issue Date: 19-Jul-2018
Publisher: The Electrochemical Society
Journal title: Journal of the Electrochemical Society
Volume: 165
Issue: 10
Start page: D444
End page: D451
Abstract: Unveiling dissolved species in electrodeposition baths helps our understanding of electrodeposition behavior, such as growth orientation. A highly concentrated aqueous alkaline copper(II)–lactate solution is used for the electrodeposition of copper(I) oxide (Cu₂O) thin films with <111> orientations; the semiconductor properties of these films facilitate their use in solar-cell materials, photocathodes, and photocatalysts. However, the dissolved species, presumably copper(II)–lactate complexes, cannot be deduced on the basis of known thermodynamic data, and have not been convincingly determined yet. In this work, we determine these cupric complexes by pH titration, ultraviolet–visible spectroscopy, and electrospray-ionization mass spectrometry (ESI-MS), including probe-ESI-MS (PESI-MS). Using PESI-MS, we successfully analyzed a highly concentrated solution without sample dilution. The determined complexes are Cu(H₋₁L)L⁻ and Cu(H₋₁L)₂²⁻ (CH₃CH(O⁻)COO⁻) is a lactate ion with a deprotonated α-hydroxyl group. As far as we know, this is the first direct experimental observation of H₋₁L²⁻ ions in a highly concentrated aqueous alkaline copper(II)–lactate solution. We also propose that H₋₁L²⁻ is stabilized by the high concentration and through coordination to copper(II) ions.
Description: This was Paper 1628 presented at the Honolulu, Hawaii, Meeting of the Society, October 2–7, 2016.
Rights: © The Author(s) 2018. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY,, which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.
DOI(Published Version): 10.1149/2.0831810jes
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