Engineering Headlines

Vienna University of Technology finds solution!

Fuel Cells live longer!Too little oxygen

Viennese researchers have discovered why high-temperature cells with novel cathodes become increasingly ineffective with time. Strontium blocks access to oxygen. And the Viennese also have a solution to the problem.

Ceramic fuel cells operating at a temperature of 450 to 1000 ° C have the highest efficiency.

The high temperature does not make it easy to deal with them. They are unsuitable for mobile use, in electric cars.

There are materials, such as the exotically sounding strontium-doped lanthanobobaltate (LSC), which also allows the cell to work at lower temperatures.

But the tiring with time, because too little oxygen from the air to the reaction space penetrates.

Inviting surface

Now scientists from the Vienna University of Technology have solved the problem. Ghislain Rupp from the Institute for Chemical Technologies and Analytics and his team suspected that the surface of the material is important.

It must have a certain inviting effect on air oxygen, so that it can become absorbed through the material and reach the reaction space.

Here, it combines with hydrogen. This creates electricity and heat as well as water as a “waste product”.

Laser pulses modify the cathode

The researchers developed a method by which they could selectively alter the surface and measure the effects on oxygen uptake.

“With a laser pulse, we evaporate various materials, which then accumulate in tiny amounts on the surface,” explains Rupp.

“This allows us to fine tune the composition of the cathode surface and, at the same time, to observe how the resistance of the system changes.” This resistance is decisive for the usefulness of the material as a cathode in the fuel cell.

Strontium is self-sufficient

The team experimented with different materials.

They found, for example, that an overdose hurts strontium on the surface.

Quite without strontium, which is used, among other things, in fireworks it makes for a red coloring – but it is not.

It depends on the distribution mainly on the surface. “If strontium atoms dominate there, oxygen is only very difficult to install,” says Rupp. Cobalt, on the other hand, has an inviting effect on the oxygen atoms. Here the storage works well.

With this finding, the Viennese researchers were able to explain why the material becomes more and more impermeable to oxygen.

During the operation of the fuel cell, strontium migrates from the interior of the ceramic to the surface and covers the cobalt zones. The door closes slowly for oxygen.

Technical use is approaching

“We have thus made an important step closer to the technical use of the material LSC for fuel cells,” says Rupp.

“Our new research method, which combines high precision coating with electrical measurement, will certainly play an important role in other areas of solid state ionics.”

What temperatures can be reached is still open.

In addition, the researchers now have to find a way to stop the movement of the strontium, but at least prevent the strontium atoms from overlapping the cobalt.

Apart from Rupp, Professor Jürgen Fleig and a group of Prof. Andreas Limbeck, both from the Institute for Chemical Technologies and Analytics of the Vienna University of Technology, are part of the team.

The British company Intelligent Energy has developed a drone with a hydrogen drive. Instead of normal batteries, she has fuel cells on board.

The drive sits on top of the flying object and weighs only 1.5 kg with tank. This is more than a battery pack, but its reserves are still significantly larger.

The drone will be able to stay in the air for two hours.

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