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MIT Researchers Discover Perovskite Sheets Can Improve Solid Oxide Fuel Cells' Efficiency


Sometimes, materials in bulk sizes exhibit properties totally different than when they are sliced in pieces only a few molecules wide. A news report from the MIT says that prof. Yang Shao-Horn and a team of researchers have discovered how a very thin sheet of a material called “strontium-substituted lanthanum cobalt perovskite,” aka LSC, can help solid oxide fuel cells (SOFC) produce a lot more electricity from the same amount of fuel.

Solid oxide fuel cells are a class of fuel cell characterized by the use of a solid oxide material (or ceramic) as the electrolyte. In contrast to proton exchange membrane fuel cells (PEMFCs), which conduct positive hydrogen ions (protons) through a polymer electrolyte from the anode to the cathode, the SOFCs use a solid oxide electrolyte to conduct negative oxygen ions from the cathode to the anode. The electrochemical oxidation of the oxygen ions with hydrogen or carbon monoxide thus occurs on the anode side.

Currently, the efficiency of SOFCs is about 60 percent. They operate at a very high temperature, up to 1000°C, and don’t use the expensive platinum catalyst. What the MIT team found is that if thin films of a mineral called perovskite are deposited as a thin layer of a crystal of zyrconia, they can boost the reaction of the cathode with oxygen, overcoming a major issue that this kind of fuel cells have.In addition to the increased reactivity, the fuel cell only works at 500 degrees Celsius, which greatly slows the fuel cell’s degradation over time.

The scientists are currently working on finding an explanation on why the LSC in thin nanometric sheets reacts that good and the bulk-sized one doesn’t. They assume that the increased reactivity of the material may result from a stretching of the surface. This may change the content of oxygen vacancies or the electronic structure of the material, possibilities that are being examined in Shao-Horn’s group. Previous research has found that some thin films of perovskite material are hundreds of times less reactive than the combination Shao-Horn’s team discovered.

Solid oxide fuel cells are currently used mainly in the industry, because of their huge capacity of generating electricity from fuels (up to 2 MW per fuel cell). If scientists will find materials for their electrodes that react at lower temperatures and with greater efficiency, maybe someday we’ll see the old coal-powered plants transformed into fuel cell plants, and fed with methanol or some other kind of cleaner fuel – even hydrogen.

[source: MIT]

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