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Highly durable electrocatalyst for use in polymer electrolyte membrane fuel cells

 Kyushu University announced on 24th November 2015, that the research group led by Professor Naotoshi Nakashima of International Institute for Carbon Neutral Energy Research (I2CNER) has succeeded in demonstration of highly durable electrocatalyst for use in polymer electrolyte membrane fuel cells (PEMFCs). Details were published in Scientific Reports*.

 The research group has already developed an electrocatalyst, which are composed of Pt-deposited polybenzimidazole-coated carbon nanotubes (CNTs) for use in PEMFCs. Polybenzimidazole (PyPBI) works as a CNT-solubilizer as well as a binder for homogeneous loading of Pt-nanoparticles (Pt-NPs). Although the electrocatalyst showed high performance when used in PEMFCs at high operating temperature (ca 120℃) with polyvinylphosphonic acid as electrolyte, this high temperature PEMFCs has not yet been in commercial production stage.

 In this study, a catalyst coated with Nafion as electrolyte is used for conventional PEMFCs that are operated at low temperatures (ca 70℃). In the fabrication of the catalyst, the pristine CNTs were wrapped with PyPBI with the deposition of Pt-NPs, and then over coated with Nafion. By using this catalyst, a high FC performance with a power density of 375 mW/cm2 was obtained, and a durability of 500,000 accelerated potential cycles was recorded with only a 5% loss of the initial FC potential and 20% loss of the maximum power density. These results of the CNTs base catalyst were far superior compared to those of the membrane electrode assembly prepared using conventional carbon black (CB) base catalyst of similar composition.

 This study shows that the replacement of the CB-based FC catalyst with the developed catalyst would remarkably improve the total performance of the conventional PEMFCs.

*Mohamed R. Berber, Inas H. Hafez, Tsuyohiko Fujigaya, and Naotoshi Nakashima, "A highly durable fuel cell electrocatalyst based on double-polymer-coated carbon nanotubes", Scientific Reports, Vol. 5, Article number: 16711 (2015); doi: 10.1038/srep16711, Published online: 23 November 2015