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Physical and electrochemical properties of cobalt doped (ti,ru)O2 electrode coatings
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.ORCID iD: 0000-0001-7329-3359
Applied Electrochemistry, School of Chemical Science and Engineering, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden .
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2013 (English)In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, Vol. 178, no 20, 1515-1522 p.Article in journal (Refereed) Published
Abstract [en]

The physical and electrochemical properties of ternary oxides Ti 0.7Ru0.3-xCoxO2 (x = 0.093 and x = 0) have been investigated and compared. Samples of three different thicknesses were prepared by spin-coating onto polished titanium to achieve uniform and well-defined coatings. The resulting electrodes were characterized with a variety of methods, including both physical and electrochemical methods. Doping with cobalt led to a larger number of micrometer-sized cracks in the coating, and coating grains half the size compared to the undoped samples (10 instead of 20 nm across). This is in agreement with a voltammetric charge twice as high, as estimated from cyclic voltammetry. There is no evidence of a Co 3O4 spinel phase, suggesting that the cobalt is mainly incorporated in the overall rutile structure of the (Ti,Ru)O2. The doped electrodes exhibited a higher activity for cathodic hydrogen evolution compared to the undoped electrodes, despite the fact that one third of the active ruthenium was substituted with cobalt. For anodic chlorine evolution, the activity was similar for both electrode types.

Place, publisher, year, edition, pages
2013. Vol. 178, no 20, 1515-1522 p.
Keyword [en]
Chlorine evolution, Cobaltdoping, DSA®, Hydrogen evolution, Polarization curves, XRD
National Category
Natural Sciences
URN: urn:nbn:se:miun:diva-17211DOI: 10.1016/j.mseb.2013.08.018ISI: 000327830000024ScopusID: 2-s2.0-84887055267OAI: diva2:561315
Available from: 2012-10-18 Created: 2012-10-18 Last updated: 2014-01-08Bibliographically approved
In thesis
1. Nanoscaled Structures of Chlorate Producing Electrodes
Open this publication in new window or tab >>Nanoscaled Structures of Chlorate Producing Electrodes
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sodium chlorate is mainly used for production of chlorine dioxide (a pulp bleaching agent). Sodium chlorate is produced by an electrochemical process where chloride ions (from sodium chloride dissolved in water) are oxidized to chlorine on the anodes and hydrogen is evolved on the cathodes. The anode of this process consists of a metal plate coated with a catalytically active metal oxide film. The electrocatalytic properties of the anode coating film have been widely investigated due to the great importance of these electrodes in the electrochemical industry. The material properties are, however, not as well investigated, and the studies described in this thesis are an attempt to remedy this.

Several standard material characterization methods were used, such as SEM, TEM, AFM, EDX, XRD, porosimetry and DSC. Also, a novel model system based on spin coated electrode films on smooth substrates was developed. The model system provided a way to design samples suitable for e.g. TEM, where the sample thickness is limited to maximum of 100 nm. This is possible due to the ability to control the film thickness by the spinning velocity when using the spin coating technique.

It was shown here that the anode coating has a nanostructure. It consists of grains, a few tens of nanometers across. The nanostructure leads to a large effective area and thus provides an explanation of the superior catalytic properties of these coatings. The grains were also shown to be monocrystalline. The size of these grains and its origin was investigated. The calcination temperature, the precursor salt and (if any) doping material all affected the grain size. A higher calcination temperature yielded larger grains and doping with cobalt resulted in smaller grains and therefore a larger real area of the coating. Some preparation conditions also affected the microstructure of the coating; such as substrate roughness. The microstructure is for example the cracked-mud structure. A smoother substrate gave a lower crack density.

The cathode of chlorate production is usually an uncoated metal plate, therefore 'less catalytically active'. It is, however, possible to activate the cathode by for example in situ additions to the electrolyte. It was shown here that sufficient addition of molybdate to the electrolyte resulted in a molybdenum film deposited on the cathode and thereby an increase of its surface area and an activation the hydrogen evolution reaction.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University, 2012
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 134
National Category
Natural Sciences
urn:nbn:se:miun:diva-17206 (URN)978-91-87103-35-3 (ISBN)
Public defence
2012-11-09, M102, 13:15 (Swedish)
Available from: 2012-10-18 Created: 2012-10-17 Last updated: 2012-11-30Bibliographically approved

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