Kyushu team develops multifunctional catalyst for poison-resistant hydrogen fuel cells; both H2 and CO as fuel
Researchers at Kyushu University, Japan, have developed the first catalyst that can oxidize both hydrogen and carbon monoxide, depending on the pH of the reaction system. Carbon monoxide is a common pollutant in commercially available hydrogen gas but it poisons the platinum catalysts used in today’s fuel cells. A paper on the work appears in the journal Angewandte Chemie International Edition.
The new catalyst, based on a nickel-iridium [NiIr] complex, mimics the behavior of two enzymes: hydrogenase in acidic media (pH 4-7) and carbon monoxide dehydrogenase in basic media (pH 7-10). The team, led by Prof. Seiji Ogo, constructed a proof-of-concept fuel cell that turned the tables on carbon monoxide poisoning by using it as a fuel and generated energy from a 1:1 mixture of the two gases.
The researchers were able to isolate various intermediates in the oxidation processes to confirm the mechanisms of hydrogen and carbon monoxide oxidation by the catalyst.
We found that the catalyst reacted with hydrogen to form a hydride complex under acidic conditions. In addition, the catalyst readily coordinated with carbon monoxide, which was oxidized to carbon dioxide, under basic conditions.—first author Professor Seiji Ogo
The team then investigated the resistance of the catalyst to poisoning by carbon monoxide in a prototype fuel cell using feed gases of hydrogen, carbon monoxide, and a 1:1 mixture of the two. The power density of the fuel cell containing the catalyst depended on the system pH and feed gas composition.
Oxidation of hydrogen by the catalyst was facilitated at low pH (acidic conditions) and oxidation of carbon monoxide was faster at high pH (basic conditions); these trends correspond well with the behavior observed for the related enzymes.
The ability of our catalyst to use both hydrogen and carbon monoxide as energy sources represents an important advance in hydrogen technology.—Professor Ogo
The scientists anticipate that catalysts for hydrogen oxidation that can resist carbon monoxide poisoning will allow development of hydrogen fuels cells with improved performance.
Seiji Ogo, Yuki Mori, Tatsuya Ando, Takahiro Matsumoto, Takeshi Yatabe, Ki-Seok Yoon, Hideki Hayashi and Masashi Asano (2017) “One Model, Two Enzymes: Activation of Hydrogen and Carbon Monoxide” Angewandte Chemie International Edition doi: 10.1002/anie.201704864