Korean Chemical Engineering Research, Vol.44, No.6, 597-601, December, 2006
산소 라디칼에 의한 Nafion 막의 열화
Degradation of Nafion Membrane by Oxygen Radical
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초록
고분자 전해질 연료전지에서 산소라디칼(OH, HO2)에 의한 나피온 고분자막의 열화를 연구하였다. 산소라디칼 형성을 위해 과산화수소(10-30％)와 황산암모늄철(1-4ppm)을 이용해 Fenton 용액을 제조하고, 80℃에서 막을 일정 시간 열화 하여 막의 특성 변화를 측정하였다. 열화 후 고분자 막의 C-F, S-O, C-O 결합이 산소 라디칼의 공격으로 끊어짐을 보였다. C-F 결합의 끊어짐으로 인해 막의 기계적 강도가 감소하고 pinhole이 발생했으며 이로 인해 수소가 막을 통과하는 양이 증가하였다. S-O와 C-O결합의 파괴로 전해질 막의 이온교환능력(IEC)이 감소함을 보였다. 30％ H2O2에 4 ppm Fe2+이 첨가된 용액에서 48시간 열화시킨 막을 이용해 단위전지 성능을 측정한 결과 정상적인 막 성능의 약 1/2로 감소했다.
The degradation of the Nafion membrane by oxygen radical (OH, HO2) was investigated in Polymer electrolyte membrane fuel cell (PEMFC). Nafion membrane was degraded in Fenton solution consisted with hydrogen peroxide (10-30％) and ferrous ion (1-4 ppm) at 80 °C. After degradation in Fenton solution, C-F, S-O and C-O chemical bonds of membrane were broken by oxygen radical attack. Breaking of C-F bond reduced the mechanical strength of Nafion membrane, and hence induced pinholes, resulting in increase of H2 crossover through the membrane. Decomposition of S-O and C-O bonds decreased the ion exchange capacity of the electrolyte membrane. The performance of unit cell composed the membrane, which was degraded in 30％ H2O2 with 4ppm Fe2+ solution for 48 hr, was about half times as low as one with normal membrane.
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