Oxygen reduction reaction in acid medium at iron phthalocyanine dispersed on high surface area carbon substrate:: tolerance to methanol, stability and kinetics
Oxygen reduction reaction in acid medium at iron phthalocyanine dispersed on high surface area carbon substrate:: tolerance to methanol, stability and kinetics
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DOI：
10.1016/j.jelechem.2004.11.034
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发表时间：
2005-04-01
影响因子：
4.5
通讯作者：
Léger, JM
中科院分区：
文献类型：
--
作者：
Baranton, S;Coutanceau, C;Léger, JM
研究了分散在高表面积碳基材 (Vulcan XC 72) 上的铁酞菁 (FePc) 在酸性介质中的电催化性能。将含有 O-2 饱和电解质的甲醇中 FePc/C 催化剂上的氧还原极化曲线与铂催化剂上获得的氧还原极化曲线进行了比较。结果清楚地表明，FePc/C 催化剂对甲醇的存在完全不敏感，并且在低过电势下成为比 Pt/C 催化剂更好的氧化还原反应（orr）催化剂，这表明 FePc/C 催化剂是铂基催化剂的良好替代品，作为低工作温度燃料电池的阴极催化剂。该催化剂在酸性介质中的主要问题是长期稳定性差，电化学测量证明了这一问题，并通过原位红外反射光谱实验对其进行了表征。红外光谱表明，FePc 降解是通过两个质子取代大环的中心金属而发生的，导致形成游离碱酞菁，已知该酞菁对氧还原催化不活跃。从该观察结果可以看出，通过使用气体扩散电极可以提高FePc的稳定性。在此条件下，室温下以-25 mA cm(-2)的恒定电流密度在FePc/C电极上进行氧还原至少24 h。最后，不同电极旋转速率 0 下的循环伏安实验确定了 Kouteck-Levich 图，其中表明 FePc/C 电极上的 orr 动力学参数与铂颗粒上获得的动力学参数相似。 FePc/C 催化剂上 orr 期间交换电子的总数 n(t) 通过旋转环盘电极实验确定，导致 nt 接近 3.9-4。 (c) 2004 Elsevier B.V. 保留所有权利。
The electrocatalytic performance of iron phthalocyanine, FePc, dispersed on a high surface area carbon substrate (Vulcan XC 72) was investigated in acid medium. The polarisation curve of oxygen reduction on the FePc/C catalyst in a methanol containing O-2-saturated electrolyte was compared to that obtained on a platinum catalyst. Results showed clearly that FePc/C catalyst is totally insensitive to the presence of methanol and becomes a better catalyst than the Pt/C catalyst for the oxidation reduction reaction (orr) at low overpotentials, indicating that FePc/C catalyst is a good alternative to platinum based catalysts as a cathode catalyst for low working temperatures fuel cells. The major problem of this catalyst in acid medium is its poor long-term stability, which was demonstrated by electrochemical measurements and characterized by in situ infrared reflectance spectroscopy experiments. The infrared spectra showed that FePc degradation occurred via the substitution of the central metal of the macrocycle by two protons, leading to the formation of a free base phthalocyanine which is known to be inactive for oxygen reduction catalysis. From this observation, it was possible to improve the FePc stability by using a gas diffusion electrode. Under these conditions, oxygen reduction was performed on a FePc/C electrode for at least 24 h with a constant current density of -25 mA cm(-2) at room temperature. Finally, cyclic voltammetry experiments at different electrode rotation rates 0 led to determine the Kouteck-Levich plots from which it was shown that the kinetic parameters for the orr at FePc/C electrodes are similar to those obtained at platinum particles. The total number of exchanged electrons n(t) during the orr on the FePc/C catalyst was determined by rotating ring disc electrode experiments leading to nt close to 3.9-4. (c) 2004 Elsevier B.V. All rights reserved.