The addition of extremely small crystals to solid electrolyte material has the potential to considerably raise the efficiency of fuel cells.
Researchers at TU Delft were the first to document this accurately, and this week their second article on the subject in a very short time was published in the scientific journal, Advanced Functional Materials.
The researchers at the Faculty of Applied Sciences at TU Delft were concentrating their efforts on improving electrolyte materials. This is the material between two electrodes, for example 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.
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. “It would therefore be preferable to have an electrolyte made of solid matter,” says PhD student drs.Lucas Haverkate. “Unfortunately though, that has disadvantages as well. The conductivity in solid matter is not as good as it is in a liquid.”
Traffic jam on the motorway
“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.”
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 in this case. “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,” concludes Haverkate.