Nicola Gaston

Nicola Gaston

Hydrogen fuel cells have shown great promise in recent years as an alternative, less environmentally harmful way to power the world’s ever expanding fleet of vehicles. However one of the main obstacles to their wider uptake is the fact that they currently rely on a rare and expensive metal – that is, platinum – to function.

Enter Nicola Gaston, one of a number of IRL scientists hard at work trying to find cheaper alternatives to this precious element, and whose efforts could ultimately broaden the application of a technology with the potential to limit the use of polluting fossil fuels.

“Platinum is an ideal catalyst for the oxidation of hydrogen and at present a necessary part of a hydrogen fuel cell,” explains Nicola, who came to IRL two years ago on a NZ Science and Technology post-doc fellowship, funded by FRST^[?], in 2007. “But we can estimate there’s not even enough platinum in the world to produce fuel cells for the US’ cars, let alone the rest of the world,” she says.

Under the direction of Shaun Hendy, IRL research scientist and deputy director of the MacDiarmid Institute for Advanced Materials and Nanotechnology, Nicola and fellow researcher Bridget Ingham have been seeking alternative electrocatalysts in collaboration with Cambridge University researchers. “Because there’s so little platinum in the world and it’s really expensive it would be nice to have other materials you could slap into a fuel cell instead,” she says.

Nicola's part in this international undertaking includes applying her expertise in materials modelling and surface chemistry to interpreting the results of experiments conducted by Bridget Ingham at the Australian Synchotron in Melbourne, and synchotron facilities at Brookhaven and Stanford in the US, into these alternative catalysts.

One of the two alternatives that have so far shown promise is tungsten carbide; the other an unstable mix of nickel and carbon, made by bombarding a target with nickel and carbon atoms in a gas chamber until it settles into a “metastable” form.

Though this second material doesn’t exist in a stable form, it works very well, says Nicola. “Which is odd because nickel itself works (as an electrocatalyst) but it dissolves immediately in the acid that these fuel cells run in, and carbon doesn’t work. But having a mix works and it doesn’t dissolve.”

Modelling the interactions between nickel and carbon as a current was applied, it appeared that the nickel atoms somehow coalesced into clusters and were trapped by the carbon, says Nicola. “These seem to be the first electrocatalysts that are ‘passivated’ by carbon. Which is quite unusual and interesting.”

She reports that the Cambridge researchers are now seriously trying to build a fuel cell that contains absolutely no platinum or platinum-like metals but just these cheap metal and carbon-based catalysts.

However, Nicola's work at IRL is not all applied – she’s also involved in pushing back the boundaries of fundamental science, and in November 2008 began work on a new, Marsden Fund-supported project to delve into the unusual properties of the element known as gallium.

Though a chemist by training, it was Nicola's PhD research into mercury clusters that paved the way for this investigation into the superheating of gallium clusters. “It was kind of a strange thing for a chemist to do because chemists usually deal with multiple kinds of atoms,” she says.  “Usually we assume that the elements, which have been known for hundreds of years, are really well understood – but it turns out this isn't always the case.”

 “Gallium’s really weird,” she explains. "First of all, it melts at 30 degrees C – just above room temperature – leaving droplets on your skin – not unlike mercury in that respect." However, gallium turns out to have some very different properties from the subject of her PhD. 

For instance, in its solid form, gallium doesn’t fracture along nice planes like most metals, but rather like glass or obsidian, she says.

And while it has long been suspected that gallium might be considered a ‘molecular metal’ – i.e. instead of there being individual metal atoms within the metal structure you have metal molecules – nobody has ever dared come out and say it directly.

“What I discovered when I started looking at it and putting it in the context of these superheating clusters is it looks like the temperature gallium melts at corresponds to a melting transition of molecules.

“Having said that, there are also experiments on aluminium and tin clusters that show some of the same behaviour, so there’s still a lot to be worked out.”

Although this research is being conducted without a particular industrial application in mind, Nicola Gaston says that since gallium is used extensively in semiconductors, her results might foreseeably impact on the electronics industry, where the thrust is towards increasing miniaturisation.

 “The more we can understand about how things change as you go to nano-sized particles the further we are going to be able to extend various forms of technology and electronics are the first example.”

With professional and personal interests spanning the nano-scale to the wider environment (Nicola is a keen tramper), it’s fitting that her studies of the very small have also given her the opportunity to see the world at large, taking her to places as varied as the UK, US, Korea, Sydney, Helsinki, and Berlin.

Indeed, after completing her PhD at Massey University, Nicola's first post-doctoral research took her to the esteemed Max Planck Institute for the Physics of Complex Systems in Dresden, Germany, where a keen ear for languages, proven during her undergraduate studies at Auckland, helped her pick up the language along the way.

Her two years in Dresden “was basically trying to take methods of quantum chemistry and apply them to solid state physics,” she says. It was a fruitful period, yielding some ‘interesting results on zinc and cadmium’ and leading Nicola to predict some new possible structures for zinc. “And though the results are very preliminary, I was told just recently that someone may have succeeded in making one of these.”