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Current oscillations during chronoamperometric and cyclic voltammetric measurements in alkaline Cu(II)-citrate solutions
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för materialkemi.
2008 (Engelska)Ingår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, nr 5, s. 2188-2197Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

It is demonstrated that current oscillations can be observed during chronoamperometric and cyclic voltammetric experiments in solutions containing 0.4 M CuSO4 and 1.2 M citrate at pH 11 and 50 degrees C. The oscillations, which are shown to originate from local variations in the pH, result in the deposition of nanostructured Cu and Cu2O materials. It is concluded that the current oscillations are analogous to the previously described potential oscillations obtained under controlled current conditions in alkaline Cu(II)-lactate, -tartrate and -citrate solutions. Rotating disk electrode results clearly show that the reduction of the Cu(II)-complexes is kinetically controlled and that the rate of the reduction increases with increasing pH and temperature. It is also shown that the presence of a cathodic peak on the anodic scan in the cyclic voltammograms can be used to identify the experimental conditions leading to the spontaneous current (or potential) oscillations. Electrochemical quartz crystal microbalance results indicate that the cathodic peak stems from an increased rate of the reduction of the Cu(II)-citrate complexes due to a rapid increase in the local pH. This causes Cu2O rather than Cu to be deposited which, however, results in a decrease in the local pH and a decreasing current. In situ ellipsometry data confirm that Cu2O deposition replaces that of Cu in the potential region of the cathodic peak. The present findings should facilitate syntheses of nanolayered materials based on spontaneous potential or current oscillations.

Ort, förlag, år, upplaga, sidor
2008. Vol. 53, nr 5, s. 2188-2197
Nyckelord [en]
current oscillations, Cu, Cu2O, nanolayers, local pH variations, citrate
Nationell ämneskategori
Annan medicinsk grundvetenskap
Identifikatorer
URN: urn:nbn:se:uu:diva-96155DOI: 10.1016/j.electacta.2007.09.032ISI: 000252685900015OAI: oai:DiVA.org:uu-96155DiVA, id: diva2:170633
Tillgänglig från: 2007-09-07 Skapad: 2007-09-07 Senast uppdaterad: 2018-01-13Bibliografiskt granskad
Ingår i avhandling
1. Electrochemical Deposition of Nanostructured Metal/Metal-Oxide Coatings
Öppna denna publikation i ny flik eller fönster >>Electrochemical Deposition of Nanostructured Metal/Metal-Oxide Coatings
2007 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Electrochemical deposition finds applications in the electronics- and protective coating industries. The technique is a versatile tool for the synthesis of alloys and thin films. Knowledge of the fundamental aspects of the electrode processes enables the design of nanostructured materials. In this thesis, electrodeposition processes in solutions containing metal ion complexes were studied and new methods for the preparation of metal/metal-oxide coatings were developed and evaluated.

Metal/metal oxide coatings were electrodeposited from aqueous solutions containing metal complexes of hydroxycarboxylic acids under reducing conditions. The mass changes of the working electrode were monitored in-situ with the electrochemical quartz crystal microbalance (EQCM) technique and ellipsometry was used to detect the formation of Cu2O. The coatings were further characterized with XRD, XPS, SEM, TEM, and Raman spectroscopy. Electrochemical methods, including reduction of Sb/Sb2O3 in an organic electrolyte, were also used to study the properties of the deposited materials.

Nanostructured coatings of Cu/Cu2O were obtained during spontaneous potential or current oscillations in alkaline Cu(II)-citrate solutions. The oscillations were due to local pH variations induced by a subsequent chemical step and comproportionation between Cu and Cu2+. Well-defined layers of Cu and Cu2O could be prepared by a galvanostatic pulsing technique, allowing independently controlled thickness of several hundred nanometers. Coatings, containing Sb and co-deposited, nanograins of Sb2O3, with a thickness of up to 200 nm were prepared from poorly buffered Sb(III)-tartrate solutions. Galvanostatic cycling showed that the latter material could be reversibly charged and discharged in a Li-ion battery for more than 50 cycles with a capacity of 660 mAh/g.

The results show that precipitations of metal oxides can occur due to local pH increases during electrochemical deposition from metal complexes with ligands containing hydroxyl groups. The ability to deposit metal oxides using cathodic deposition relies on a sufficiently slow reduction of the oxide.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2007. s. 54
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 336
Nyckelord
Inorganic chemistry, electrochemical deposition, local pH, Cu2O, Sb2O3, complex, EQCM, reduction, Oorganisk kemi
Identifikatorer
urn:nbn:se:uu:diva-8186 (URN)978-91-554-6956-6 (ISBN)
Disputation
2007-09-28, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 14:00
Opponent
Handledare
Tillgänglig från: 2007-09-07 Skapad: 2007-09-07 Senast uppdaterad: 2011-03-25Bibliografiskt granskad

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