Researchers at TU Delft have identified a new huge potential of nanocrystals in fuel cells.  The Delft researchers are the first to document the idea accurately with their second article on the subject. The latest paper was published in the scientific journal, Advanced Functional Materials.

The addition of the extremely small nanocrystals to a solid electrolyte material is showing the potential to considerably raise the efficiency of solid electrolyte fuel cells.  The electrolyte is usually a liquid, but this has a number of drawbacks. The liquid has to be very well enclosed, for example, and it takes up a relatively large amount of space.

PhD student Lucas Haverkate said, “It would therefore be preferable to have an electrolyte made of solid matter. Unfortunately though, that has disadvantages as well. The conductivity in solid matter is not as good as it is in a liquid.”

This points up the researchers initial goal. The team at TU Delft was concentrating their efforts on improving electrolyte materials, the material between two electrodes used in a fuel cell or a battery. The better the characteristics of the electrolyte, the better, more compactly or more efficiently the fuel cell or battery works.

Haverkate continues, “In a solid matter you have a network of ions, in which virtually every position in the network is taken. This makes it difficult for the charged particles (protons) to move from one electrode to another. It’s a bit like a traffic jam on a motorway. What you need to do is to create free spaces in the network.”

Haverkate explains that one of the ways of achieving this, and therefore of increasing conductivity in solid electrolytes, is to add nanocrystals (of seven nanometres to around fifty nanometres), of titanium dioxide.” A characteristic of these TiO2 crystals is that they attract protons, and this creates more space in the network.” The nanocrystals are mixed in the electrolyte with a solid acid (CsHSO4). This latter material ‘delivers’ the protons to the crystals. “The addition of the crystals appears to cause an enormous leap in the conductive capacity, up to a factor of 100.”

That kind of conductivity improvement is going to have a worthwhile impact.  A reduction in the resistance is implied, thus one of the sources of heat should be reduced.

This is a remarkable achievement by the TU Delft team and has led to two publications in the scientific journal Advanced Functional Materials. Last December, Haverkate published an article on the theory behind the results. His fellow PhD student, Wing Kee Chan, is the main author of a second paper that’s appeared in the same publication this week. Chan focused on the experimental side of the research. “The nice thing about these two publications is that the experimental results and the theoretical underpinning strongly complement each other,” says Haverkate.

Chan carried out measurements on the electrolyte material using the neutron diffraction method. This involves sending neutrons through the material. The way in which the neutrons are dispersed makes it possible to deduce certain characteristics of the material, such as the density of protons in the crystals. Haverkate comments satisfyingly, “It is the first time that measurements have been taken of solid-material electrolytes in this way, and on such a small scale. The fact that we had nuclear research technologies at the Reactor Institute Delft at our disposal was tremendously valuable.”

This is just the first step.  The combination of TiO2 and CsHSO4 does not mark the end of the search for a suitable solid-material electrolyte, but does show promising beginning.

Other material combinations will be tested that may achieve better scores in the area of stability.  Professor Fokko Mulder, who is Haverkate’s and Chan’s PhD supervisor, says. “At this stage, we are more concerned about acquiring a fundamental understanding and a useful model, than the concrete issue of finding out what the most suitable material is. It is important that we identify the effect of nanocrystals, and give it a theoretical basis. I think there is great potential for these electrolytes. They also have the extra benefit of continuing to function well over a wide range of temperatures, which is of particular relevance for applying them in fuel cells.”

Maybe the professor is right, but a lot of fuel cells minds are going to be focusing on those two papers from the Delft team.  Some might not wish to wait for theory before tests and trials.  An increased temperature operating range for fuel cells and reduced heat output losses from internal resistance are going to be very welcome improvements.


2 Comments so far

  1. Musson on March 30, 2011 8:35 AM

    Reminds me of how the folks at Eestor put their high permittivity powders into a gel.

  2. Benjamin Cole on March 31, 2011 8:30 PM

    How long until some of these recent discoveries become commercial? I think that should be a regular feature of every one of your stories. Keep up the great work.

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