결정성 탄소의 산처리가 고분자연료전지의 성능과 내구성에 미치는 영향 평가
Effect of Acid Treatment of Graphitized Carbon on Carbon Corrosion in Polymer Electrolyte Membrane Fuel Cells
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carbon nanofiber (CNF)의 표면을 질산과 황산을 사용하여 산화시킨 후 백금 촉매를 modified polyol method로 담지시켰다. 산처리 시간이 길어질수록 탄소 표면에 산소 작용기의 양이 증가 했으며 그 결과 백금 담지량이 증가하고 분산도가 향상되었다. CNF의 산처리 시간이 전기화학적 부식특성에 미치는 영향을 평가하기 위해서 단위전지형태에서1.4 V의 정전압 조건을 30분간 인 가하였으며 이 때 발생한 CO2 의 양을 on-line mass spectrometry로 측정하였다. 실험 결과 산처리한 CNF를 사용한 Pt/CNF 촉매가 산처리 하지 않은 CNF를 담체로 사용한 경우보다 CO2 발생량이 많았으며 산처리 시간이 증가할수록 CO2 발생량이 증가하였다. 부식실험 이후 성 능감소의 폭은 카본부식이 증가할수록 증가하였다. 이는 CNF에 대한 산처리가 촉매 담지에는 유리할 수 있으나 전기화학적 카본 부식을 가속화 시키는 결과를 초래하여 결과적으로 연료전지 내구성을 저하시키는 요인이 될 수 있는 것으로 사료된다.
Abstract
Pt catalyst was adsorbed on Carbon nanofiber (CNF) by modified polyol method after acid treatment of the carbon support with HNO3 and H2SO4. As the time for acid treatment increases, more oxygen functional groups on carbon surface were produced which improve the loading amount and dispersion of Pt catalyst on carbon supports. In order to inspect the effect of CNF acid treatment time on electrochemical corrosion, constant potential of 1.4 V was applied to a single cell for 30 min and the amount of CO2 emitted was monitored with on-line mass spectrometry. According to the results of our experiment, more CO2 was produced with Pt/ oxidized-CNF catalyst in compared to that with unoxidized-CNF. Increasing acid treatment time also induces the more CO2 emission. Besides, performance degradation after corrosion test expanded with severer carbon corrosion. From the observed results, it can be concluded that the acid treatment of CNF is beneficial to catalyst loading, but it also is a significant factor declining the fuel cell durability by accelerating electrochemical oxidation of carbon support.
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