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High-Performance Hybrid Catalyst with Selectively Functionalized Carbon by Temperature-Directed Switchable Polymer

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journal contribution
posted on 14.05.2013, 00:00 by Namgee Jung, Sang Moon Kim, Do Hyun Kang, Dong Young Chung, Yun Sik Kang, Young-Hoon Chung, Yong Whan Choi, Changhyun Pang, Kahp-Yang Suh, Yung-Eun Sung
Carbon-supported Pt (Pt/C) catalyst was selectively functionalized with thermally responsive poly­(N-isopropylacrylamide) (PNIPAM) to improve water transport in the cathode of proton exchange membrane fuel cell (PEMFC). Amine-terminated PNIPAM selectively reacted with the functional group of −COOH on carbon surfaces of Pt/C via the amide reaction by 1-ethyl-3-(3-dimethylaminopropyl)­carbodiimide (EDC) as a catalyst. Pt surfaces of Pt/C were intact throughout the carbon surface functionalization, and the carbon surface property could be thermally changed. The PNIPAM-functionalized Pt/C was well-dispersed, because of its hydrophilic surface property at room temperature during the catalyst ink preparation. In sharp contrast, when PEMFC was operated at 70 °C, PNIPAM-coated carbon surface of Pt/C became hydrophobic, which resulted in a decrease in water flooding in the cathode electrode. Because of the switched wetting property of the carbon surface, PEMFC with PNIPAM-functionalized Pt/C catalyst in the cathode showed high performance in the high current density region. To explain the enhanced water transport, we proposed a simple index as the ratio of systematic pressure (driving force) and retention force. The synthetic method presented here will provide a new insight into various energy device applications using organic and inorganic composite materials and functional polymers.