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Professor Maria Skyllas-Kazacos was interviewed in 2000 for the Interviews with Australian scientists series. By viewing the interviews in this series, or reading the transcripts and extracts, your students can begin to appreciate Australia's contribution to the growth of scientific knowledge.
The following summary of Skyllas-Kazacos's career sets the context for the extract chosen for these teachers notes. The extract covers how vanadium came to be used by her team for use in redox flow batteries. Use the focus questions that accompany the extract to promote discussion among your students.
Maria Skyllas-Kazacos was born in 1951 in Kalimnos, Greece, and emigrated with her family to Australia in 1954. She received her tertiary education at the University of New South Wales, receiving a BSc (Hons) in 1974 and a PhD in 1979. Her doctoral research was in electrochemical studies of molten salts.
In 1974 Skyllas-Kazacos worked for E R Squibb and Sons Pharmaceuticals, in Athens, as a production manager.
In 1978-79 she was a CSIRO postdoctoral research fellow at Bell Laboratories, New Jersey, working on solar energy and battery research.
Skyllas-Kazacos was a Queen Elizabeth II Fellow in the School of Physics at the University of New South Wales during 1980-81. She has continued at the University of New South Wales in the School of Chemical Engineering and Industrial Chemistry and from 1982-1993 held the positions of lecturer, senior lecturer and associate professor. She was appointed professor of the school in 1993. Her research team invented the vanadium redox battery, which holds revolutionary possibilities for energy storage and energy policy, and has interests in electrode materials and processes, conducting plastics, and photooxidation.
Skyllas-Kazacos is a Fellow of both the Royal Australia Chemical Institute and the Institution of Engineers, Australia. She is a Chartered Professional Engineer, a member of the Electrochemical Society of the USA, and a member of the Australian Electric Vehicle Association. Her research has gained her many honours including the Bloom-Gutmann Award in 1980 and the R K Murphy Medal in 2000, both from the Royal Australia Chemical Institute. In 1999 she was made a Member of the Order of Australia.
Vanadium oxidation reduction: a puzzling experimental hitch
Vanadium is the obvious element [for use in a redox flow battery] – everyone knows that vanadium exists in different oxidation states – and a few other elements could work, such as tungsten, molybdenum and titanium. Professor Bob Robins had suggested that we try vanadium first, as he had been doing some research on its extraction for a minerals processing project. I decided to give vanadium a try but we hadn’t done any previous work on it, so we thought we’d apply for a grant to see if it would work. We didn’t get the grant but I was very keen to see if it was going to work anyway, and the next year I managed to get an honours project student, Elaine Sum, onto this project. In fact, she was the top student of the year, getting a university medal.
I started to get her working on different vanadium compounds and electrolyte solutions, but after a lot of trials, she could not observe any reaction. It was discouraging. But I’m the sort of person who, before I give a student a project, wants to make sure it works. So during the Christmas holiday I’d actually tried the experiment and found that it did work, but then every time she tried it, it just would not work. We went backwards and forwards in the laboratory, and finally we worked out that whereas I was doing quick, rough experiments and it was working, when she was doing things very meticulously and cleanly there were no reactions. We discovered that the key to the whole thing was the way I was scraping the electrode, which had to be roughened up to activate it.
After many years of studying all the mechanisms, and why and how things work, we now know that if you use carbon as the electrode for vanadium – which is what we were trying to do – the vanadium oxidation reduction reaction involves not only a transfer of an electron but a transfer of oxygen as well. The VO2+ has to gain an oxygen to go to VO2+, and if the carbon is too clean there aren’t any oxygen groups on the surface to allow it to grab an oxygen. Consequently it wasn’t reacting on the clean, smooth surface.
Vanadium systems: paradoxes and challenges
I have the impression from Dr Bhathal’s interview with you that there was absolutely no reason why you should have continued working on vanadium. Apparently it didn’t exist in a soluble form and from the literature you would never have predicted the results that you actually got. So what made you do it?
Well, initially you have an idea, and then of course you go to the literature to make sure that no-one else has done it before or, if it has been tried, what drawbacks and limitations there are. No-one had tried a vanadium redox battery before, but we needed to understand some of the fundamental properties of vanadium ions. The most important fundamental property of vanadium systems is that the ions must exist in highly soluble forms, because that’s how a redox flow battery works. When you charge it and discharge it, the ions have to be in solution. If they come out of solution, you’re in trouble.
So you have to check the solubilities. But often there’s not enough information on solubilities or it’s only in limited systems. You might find the solubility of vanadium in water is very low, but what if you use a different system? So you shouldn’t be turned off by what you initially read, because the literature that’s available often contains limited information and does not necessarily lead to a dead-end. There could be conditions in which all of the vanadium ions might show a reasonable sort of solubility.
When we first started looking at it, it appeared that all the oxidation states were okay except for the vanadium(V), which is extremely insoluble. We were simply hoping that we’d be able to find an electrolyte which would allow it to be dissolved in a high level, but no-one had shown or predicted that. There was nothing to actually lead us to such a conclusion; we were just hoping to find something. In fact, what we eventually discovered was that the common V(V) compounds are highly insoluble, but if we started off with the soluble V(IV) sulphate to produce a 2M V(IV) solution it was possible to charge it to the V(V) state without the V(V) coming out of solution. In fact, this turned out to be the vanadium redox battery invention and this was something that could not have been predicted. But again, it was necessary to find the right type of solution in which to dissolve the V(IV) so that we could oxidise it to V(V) as well as reduce it to V(III) and V(II).
And then you experimented with various forms and came up with the sulphuric acid?
That’s right. Vanadium is a really tricky system, a very complex element. That’s what makes it so fascinating. You could spend your whole life studying it and still not understand it. Each of its oxidation states has its own chemistry. Things behave in opposite directions. For example, if you try to increase the solubility of one ion, it then tends to reduce the solubility of one of the others. To get conditions which will allow all ions to exist at a relatively high solubility is very tricky. And then there are things like temperature. Typically, one would try increasing the temperature of the system, because all other ions will increase their solubility with temperature. But not vanadium(V). If you increase the temperature, vanadium(V) precipitates. So you’ve got to work within an operating window and try to find ways of extending it so that you can operate over greater temperature ranges. The same happens with the sulphuric acid. If you increase the concentration of sulphuric acid to get the vanadium(V) into solution, all the others start precipitating. Everything works against you. It’s a real challenge to get those conditions right so everything works together in your favour.
Focus questions
Select activities that are most appropriate for your lesson plan or add your own. You can also encourage students to identify key issues in the preceding extract and devise their own questions or topics for discussion.
ion
oxidation states
redox flow battery
solution
solubility
vanadium
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