October 17, 2019
Keio University
TOYOTA BOSHOKU CORPORATION
Institute for Molecular Science
Chiba University
Nagoya University
A research group led by Associate Professor Hironori Tsunoyama and Professor Atsushi Nakajima of the Faculty of Science and Technology at Keio University, and Chief Akiharu Onuma of TOYOTA BOSHOKU CORPORATION, in collaboration with Researcher Archana Velloth and Professor Masahiro Ehara of the Institute for Molecular Science, Professor Nobuyuki Ichikuni of the Graduate School of Engineering at Chiba University, and Professor Masao Tabuchi of the Synchrotron Radiation Research Center at Nagoya University, has discovered that the catalytic activity for the oxygen reduction reaction (ORR) of a subnanocluster composed of six platinum atoms exhibits a mass activity approximately 1.7 times higher than that of the current standard platinum catalysts used in fuel cells. Through extended X-ray absorption fine structure (EXAFS) measurements and density functional theory (DFT) calculations, they have also revealed that the structure of the highly active platinum hexamer is a bitetrahedron.
Nanoclusters, which are aggregates of a few to about a thousand atoms or molecules, are larger than individual atoms and molecules but smaller than bulk materials, and they possess properties and functions distinct from both. Because their properties can be controlled by the number of atoms, composition, and charge state, they are expected to have applications in areas such as catalysis, electronic devices, and magnetic devices. In particular, for catalysts made of precious metal elements, technologies that achieve high activity through nanoclusters—where most constituent atoms are surface atoms—while also reducing the usage of rare precious metals are gaining attention. However, because the amount of nanoclusters produced by conventional gas-phase synthesis has been extremely small, it has been very difficult to evaluate their catalytic activity from the perspective of application in fuel cells.
This research group successfully synthesized a large quantity of platinum subnanoclusters, which are sub-nanoscale aggregates of platinum atoms, in the gas phase and evaluated their oxygen reduction reaction (ORR) activity and structure. As a result, they found that these platinum hexamer subnanoclusters exhibit higher activity than standard platinum catalysts and clarified their structure from both experimental and theoretical perspectives. These findings are considered to be of high value as a fundamental technology for fuel cells. The results of this research were published in the Royal Society of Chemistry's academic journal "Chemical Communications" on September 26, 2019 (UK time).
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