Korean Chemical Engineering Research

The Korean Institute of Chemical Engineers (한국화학공학회)
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Electrochemical Behavior of Cathode Catalyst Layers Prepared with Propylene Glycol-based Nafion Ionomer Dispersion for PEMFC

프로필렌글리콜에 분산된 나피온 이오노머로 제조된 공기극 촉매층의 연료전지 성능 특성 연구

  • Woo, Seunghee (Fuel Cell Laboratory, Korea Institute of Energy Research (KIER)) ;
  • Yang, Tae-Hyun (Fuel Cell Laboratory, Korea Institute of Energy Research (KIER)) ;
  • Park, Seok-Hee (Fuel Cell Laboratory, Korea Institute of Energy Research (KIER)) ;
  • Yim, Sung-Dae (Fuel Cell Laboratory, Korea Institute of Energy Research (KIER))
  • 우승희 (한국에너지기술연구원 연료전지연구실) ;
  • 양태현 (한국에너지기술연구원 연료전지연구실) ;
  • 박석희 (한국에너지기술연구원 연료전지연구실) ;
  • 임성대 (한국에너지기술연구원 연료전지연구실)
  • Received : 2019.02.15
  • Accepted : 2019.04.15
  • Published : 2019.08.01
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Abstract

To develop a membrane electrode assembly (MEA) with lower Pt loading and higher performance in proton exchange membrane fuel cells (PEMFCs), it is an important research issue to understand interfacial structure of Pt/C catalyst and ionomer and design the catalyst layer structure. In this study, we prepared short-side-chain Nafion-based ionomer dispersion using propylene glycol (PG) as a solvent instead of water which is commonly used as a solvent for commercially available ionomers. Cathode catalyst layers with different ionomer content from 20 to 35 wt% were prepared using the ionomer dispersion for the fabrication of four different MEAs, and their fuel cell performance was evaluated. As the ionomer content increased to 35 wt%, the performance of the prepared MEAs increased proportionally, unlike the commercially available water-based ionomer, which exhibited an optimum at about 25 wt%. Small size micelles and slow evaporation of PG in the ionomer dispersion were effective in proton transfer by inducing the formation of a uniformly structured catalyst layer, but the low oxygen permeability problem of the PG-based ionomer film should be resolved to improve the MEA performance.

고분자연료전지용 막전극접합체(Membrane Electrode Assembly, MEA)의 저가화 및 고성능화를 위하여 촉매층을 구성하는 촉매와 이오노머의 계면 특성에 대한 이해가 중요한 연구주제가 되고 있다. 본 연구에서는 이오노머의 구조 제어를 위하여 상용 이오노머의 용매로 사용되는 물 대신에 프로필렌글리콜(Propylene Glycol, PG)을 용매로 사용하여 단측쇄(Short Side Chain, SSC) 나피온 이오노머가 분산된 현탁액을 제조하고 이를 이용하여 공기극 촉매층을 제조하여 연료전지 성능 특성을 평가하였다. PG 기반 이오노머의 함량을 20~35 wt%로 증가시키면서 제조된 촉매층의 연료전지 성능은 상용 물 기반 이오노머와는 달리 이오노머 함량이 35 wt%까지 증가함에 따라 성능도 지속적으로 증가하였다. PG 기반 이오노머의 작은 입도와 느린 건조 속도는 균일 구조의 촉매층 형성을 유도하여 수소이온전달에는 효과적이었지만 PG 기반 이오노머 필름의 낮은 산소투과도는 MEA 성능을 저하시키는 주요 문제로서 개선이 필요하였다.

Keywords

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Fig. 1. (a) N2 adsorption and desorption isotherms and (b) BJH desorption pore size distribution of the commercially available Pt/C catalyst.

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Fig. 2. Hydrodynamic diameter of the 25 wt%, 3 wt% Nafion ionomer dispersed in water and PG.

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Fig. 3. Surface morphology of the catalyst layers prepared with (a) water and (b) PG-based Nafion ionomers observed by SEM.

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Fig. 4. I-V and HFR curves of MEAs prepared with different contents of PG-based ionomers in a single cell at 80 ℃ ((a), (b), 100% RH, (c), (d), 50% RH).

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Fig. 5. HFR-corrected I-V polarization curves of MEAs prepared with water-based ionomer and PG-based ionomer in a single cell at 80 ℃ (a) 100% and (b) 50% RH.

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Fig. 6. H2/N2 impedance for the measurement of proton transfer resistance in cathode catalyst layers under (a) 100% and (b) 50% RH.

Table 1. Specification of prepared MEAs

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