Trace Metals Improve Fuel Cell Stability

Scientists in South Korea have used doped electrode materials with small amounts of metal to improve the chemical stability of fuel cells.

AsianScientist (Jan. 26, 2018) – Scientists in South Korea have devised a method to improve the chemical stability of electrode materials by introducing trace amounts of metal. They published their findings in the journal Energy & Environmental Science.

Fuel cells are emerging as eco-friendly and renewable energy sources. In particular, solid oxide fuel cells made of ceramic materials have been gaining attention for their ability to directly convert various forms of fuel—such as biomass and liquid natural gas—into electric energy.

The core factor that determines the performance of solid oxide fuel cells is the cathode at which the reduction reaction of oxygen occurs. Conventionally, oxides of perovskite are used in cathodes. However, despite the high performance of perovskite oxides at initial operation, the performance decreases with time, limiting their long-term use.

In particular, the high temperature oxidation state required for cathode operation leads to a phenomenon known as surface segregation, in which strontium oxide accumulates on the surface of the pervoskite oxides, resulting in decreased electrode performance. The detailed mechanism of this phenomenon remains unclear, and a way to effectively inhibit it has not been suggested.

In this study, a team of researchers led by Professor Jung WooChul at the Korea Advanced Institute of Science and Technology (KAIST) in South Korea used computational chemistry and experimental data to determine the parameters affecting surface aggregation. They observed that local compressive states around the strontium atoms in a perovskite electrode lattice weakened the Sr-O bond strength, which in turn promoted strontium segregation.

The team identified local changes in strain distribution in perovskite oxide as the main cause of segregation on strontium surface. Based on these findings, the team doped the oxides with a variety of metals to control the extent of lattice strain, effectively inhibiting strontium segregation.

“This technology can be implemented by adding a small amount of metal atoms during material synthesis, without any additional process,” said Jung. “I hope this technology will be useful in developing highly durable perovskite oxide electrodes in the future.”

The article can be found at: Koo et al. (2017) Enhanced Oxygen Exchange of Perovskite Oxide Surfaces through Strain-driven Chemical Stabilization.


Source: Korea Advanced Institute of Science and Technology; Photo: Shutterstock.
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