Research of new materials to reduce the operating temperature of solid oxide fuel cells

Plasma plume during an in situ PLD measurement. Credit: Vienna University of Technology

Researchers at TU Wien are studying new materials that can be used to reduce the operating temperature of solid oxide fuel cells. To do this, they apply an innovative method.

Solid oxide fuel cells consist of three important parts: an anode, a cathode, and an electrolyte. As the oxygen is incorporated into the cathode, the oxygen is then transported through the electrolyte to the anode, where the oxygen reacts with the hydrogen in water. The fuel cell is able to convert the energy released in the process into electricity. For this reason, fuel cells are increasingly used in stationary energy supply and in the automotive industry.

In order to reduce the operating temperature of solid oxide fuel cells from 800 ° C to 450 ° C at 600 ° C today, scientists at TU Wien are looking for alternative materials that are suitable to serve as cathodes at these lower temperatures. Markus Kubicek and his team recently published the results of their materials analysis in the Journal of Materials Chemistry A.

Reduced operating temperature

Solid oxide fuel cells have been built since the 1980s. Today, researchers are trying to develop new fuel cells that offer high long-term stability and are cheaper to manufacture. To do this, it is necessary to lower the operating temperature to about 450 ° C to 600 ° C. For the operation of the solid oxide fuel cell at lower temperatures, in particular the rather slow oxygen exchange at the cathode represents a bottleneck. Researchers around the world are therefore looking for ways to develop new electrode materials that can incorporate oxygen quickly enough, even at these lower temperatures.

Detective work on the fuel cell

Matthäus Siebenhofer and Christoph Riedl in the laboratory. Credit: Vienna University of Technology

Oxygen exchange routes

Scientists from the “Technical Electrochemistry” research division have been working on mixed conductive materials (MIEC) for years. The oxides of this class of materials are particularly well suited for fuel cell cathodes, as they can conduct both oxygen ions and electrons at higher temperatures. It works mainly via defects, i.e. minimal deviations from the ideal crystal lattice, which are intentionally introduced into the material.

“The most important defects within these materials are oxygen vacancies, electrons and holes. In order to be able to optimize these materials in a targeted manner, a better understanding of the role of these defects for the incorporation reaction oxygen is of great importance “, explains Markus Kubicek, head of the FWF project” In-situ characterization of thin films oxidized during growth “. Researchers have now succeeded in doing so.

Unique measurement technique in the world

To measure the kinetics of the oxygen incorporation reaction, the researchers use “in situ PLD” measurements, unique in the world. The electrode materials are deposited in a vacuum chamber with a laser and are measured directly after deposition by applying impedance spectroscopy. “Since even the smallest impurities can have a strong influence on the measurement results, we needed a measurement method that allows us to examine blank electrode surfaces. We managed to do it here for the first time, ”says Christoph Riedl, solid state research group. ionic. “It was only thanks to our in-situ method developed here that we were able to perfectly combine theoretical simulation and real measurement results,” he adds.

Different materials, same oxygen pathways

The researchers used their measurement method to study the oxygen exchange reaction at the surface of five promising materials. “One of the strengths of our measurements is that, for the first time, we were able to observe that the oxygen exchange reaction seems to follow the same mechanism on very different materials,” describes Matthäus Siebenhofer. “A decisive factor here is the availability of oxygen vacancies on the surface.”

Jürgen Fleig, leader of the “Solid State Ionics” working group, concludes: “In this study, we were able to combine various research results and experimental developments of recent years and thus describe and understand the most important reaction in the field of solid oxide fuel cells are much better. ”

A new facet of fuel cell chemistry

More information:
Matthäus Siebenhofer et al, Study of oxygen reduction pathways on blank SOFC cathode surfaces by in situ PLD impedance spectroscopy, Journal of Materials Chemistry A (2021). DOI: 10.1039 / D1TA07128A

Provided by Vienna University of Technology

Quote: Research for New Materials to Reduce the Operating Temperature of Solid Oxide Fuel Cells (2021, November 30) Retrieved November 30, 2021 from solid-oxide-fuel.html

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