Research Highlights

A Sulfur-Tolerant Cathode Catalyst Converting CO2

2020-02-03 96

[Won Bae Kim and his research team developed a solid oxide electrolysis cell catalyst that can split carbon dioxide.]

When coal, oil, natural gas and other fossil fuels are burned, carbon dioxide (CO2) is produced which is the main cause for environmental pollution and climate changes. For this reason, many efforts have been invested into reducing production of carbon dioxide and its decomposition and conversion into other substances with high industrial value. Recently, a research team from POSTECH has successfully developed a catalyst that can decompose carbon dioxide emitted from power plants, stealworks and other industrial settings.

Won Bae Kim, a professor of POSTECH Chemical Engineering and his student, Seong Min Park developed a cathode catalyst as a solid oxide electrolysis cell (SOEC) that could efficiently convert carbon dioxide to carbon monoxide (CO) under a carbon dioxide stream gas containing hydrogen sulfide. Their research was introduced as a featured story in the January issue of Journal of Materials Chemistry A, a prestigious global journal published by the Royal Society of Chemistry.

Electrolytic cell, which uses reverse reaction of a solid oxide fuel cell, has been used to decompose carbon dioxide. The solid oxide electrolysis cell can convert water and carbon dioxide to hydrogen and carbon monoxide and can produce syngas without additional process.

However, it requires to be tolerant to impurities such as hydrogen sulfide contained in the emitted gas in order to treat carbon dioxide emitted from the power plants or steal works and other industrial settings. Nickel based materials used in the conventional solid oxide electrolysis cell is vulnerable to hydrogen sulfide.

The research team solved the problem by facilitating the exsolution*1 phenomenon in which metal nanoparticles are spontaneously formed on the surface of the layered perovskite material. These materials have lower catalytic activities but have higher tolerance to hydrogen sulfide than the nickel-based materials. Using this property of the material, the team demonstrated a solution. When the solid oxide electrolysis cell operated, cobalt-nickel alloy nanoparticle catalyst stimulated electrolysis of carbon dioxide and overcame the low catalytic activity of perovskite. Also, the layered structures of perovskite suppressed hydrogen sulfide from anchoring on the surface and reaction and increased stability of an electrode.

The newly developed material for the solid oxide electrolysis cell can produce carbon monoxide by electrolyzing carbon dioxide of about 7.1 L/1cm2 in a day. In addition, they verified that it showed stable electrolysis without carbon depositions and deterioration under the carbon dioxide gas containing hydrogen sulfide condition for 90 hours.

Professor Won Bae Kim said, “We were able to improve electrolysis performance better than the conventional electrolysis system by using cobalt-nickel alloy nanoparticle catalyst spontaneously formed on the layered surface of perovskite. When this technology is commercialized, we expect it to directly treat carbon dioxide containing hydrogen sulfide emitted from industrial settings such as power plants or stealworks.”

This research was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Science and ICT and also by the Korea Institute of Energy Technology Evaluation and Planning and the Ministry of Trade, Industry and Energy of the Republic of Korea.

1. Exsolution
Process of separation when mixtures of metal are heated