Observation of ionomer in catalyst ink of polymer electrolyte fuel cell using cryogenic transmission electron microscopy

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• 作者：Shinichi Takahashi^a ; ^{taka-shin@mail.nissan.co.jp} ; Junichi Shimanuki^b ; Tetsuya Mashio^a ; Atsushi Ohma^a ; Hajime Tohma^b ; Ayumi Ishihara^c ; ^d ; ^e ; Yoshiko Ito^c ; ^d ; ^e ; Yuri Nishino^d ; ^e ; Atsuo Miyazawa^d ; ^e
• 关键词：Polymer electrolyte fuel cell ; catalyst ink ; catalyst layer ; ionomer ; cryogenic transmission electron microscopy
• 刊名：Electrochimica Acta
• 出版年：2017
• 出版时间：10 January 2017
• 年：2017
• 卷：224
• 期：Complete
• 页码：178-185
• 全文大小：6836 K
• 卷排序：224

文摘

Optimizing the catalyst layer structure is one of the key issues for improving performance despite lower platinum loading. The catalyst ink, consisting of platinum-loaded carbon particles and ionomer dispersed in an aqueous solvent, is a key factor for controlling the structure of the catalyst layer because the catalyst layer is prepared in a wet coating process. For that purpose, we visualized the nanostructure of the ionomer in the catalyst ink by cryogenic electron microscopy, especially cryogenic transmission electron microscopy (cryo-TEM). By cryo-TEM, it was revealed that ionomer molecules formed rod-like aggregates macro-homogeneously in the solvent, and a similar morphology was observed in a carbon-particle-containing solvent. In contrast, ionomer aggregates in the catalyst ink containing platinum nanoparticles loaded on carbon particles were denser in the vicinity of the platinum-loaded carbon particles. That can be attributed to strong interaction between platinum nanoparticles and sulfonic acid groups in the ionomer. It also implies that a good understanding of ionomer morphology in the catalyst ink can play an important role in controlling the catalyst layer microstructure for reducing platinum loading.