In Situ ATR-FTIR Analysis of the Structure of Nafion-Pt/C and Nafion-Pt3Co/C Interfaces in Fuel Cell
In Situ ATR-FTIR Analysis of the Structure of Nafion-Pt/C and Nafion-Pt3Co/C Interfaces in Fuel Cell
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DOI：
10.1021/jp306955q
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发表时间：
2012-10-11
影响因子：
3.7
通讯作者：
Uchida, Hiroyuki
中科院分区：
文献类型：
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作者：
Hanawa, Hirotaka;Kunimatsu, Keiji;Uchida, Hiroyuki
为了获得如何提高燃料电池阴极纳米催化剂的效率的线索，Nafion-Pt/C和Nafion-Pt 3Co/C在室温下完全加湿的N-2中的界面结构，首次通过原位衰减全反射傅里叶变换红外光谱（ATR-FTIR）研究，使用膜电极组件（MEA）型电池，没有任何支持电解质溶液。我们确定了四种类型的吸附物种在界面上与改变电极电位，即磺酸根阴离子（SO 3-）与醚基团（C-O-C）的Nafion侧链，水分子（吸附H2Oad和/或水合SO 3-基团），和水合质子[H+（H2O）（n）]。对于在Pt 3Co/C上形成的Pt表层，清楚地观察到归属于H+（H2O）（n）和H+（H2O）（n）的水弯曲模式δ（HOH）的带强度，（1800和1720 cm（-1））和H2Oad（1610 cm（-1））随电位增加而下降，比RHE的0.2 V更正，伴随着nu（s）（SO 3-）（1050 cm（-1））和nu（C-O-C）（965 cm（-1））的增加。这表明Nafion中带有醚侧链的SO 3-基团特异性地吸附在催化剂表面上，同时排出最初吸附在较小正电位处的H+（H2O）（n）和H2Oad。我们还发现，在Pt 3Co上形成的Pt皮肤层上的Nafion侧链中的SO 3-基团的特异性吸附的起始电位是不太积极的约。0.2 V比在Pt上，这是一个趋势，发现在我们最近的结果，通过使用电化学石英晶体微天平（EQCM）的ClO 4-阴离子在这些电极上的特异性吸附相似。
To obtain clues to how to improve the effectiveness of cathode nanocatalysts in fuel cells, the interfacial structure of Nafion-Pt/C and Nafion-Pt3Co/C in fully humidified N-2 at room temperature was, for the first time, investigated by in situ attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy by use of a membrane-electrode assembly (MEA) type cell without any supporting electrolyte solution. We identified four types of adsorbed species at the interface with changing the electrode potential, that is, sulfonate anions (SO3-) with ether groups (C-O-C) in the Nafion side chain, water molecules (adsorbed H2Oad and/or hydrating SO3- groups), and hydrated protons [H+(H2O)(n)]. For a Pt skin layer formed on Pt3Co/C, it was clearly observed that the band intensities assigned to the water bending mode delta(HOH) of both H+(H2O)(n) (1800 and 1720 cm(-1)) and H2Oad (1610 cm(-1)) decreased with increasing potential more positive than 0.2 V vs RHE, accompanied by increases in those of nu(s)(SO3-) (1050 cm(-1)) and nu(C-O-C) (965 cm(-1)). This indicates that the SO3- groups with an ether side chain in Nafion adsorbed specifically on the catalyst surface, while expelling H+(H2O)(n) and H2Oad originally adsorbed at less positive potentials. We also found that the onset potential for the specific adsorption of the SO3- group in the Nafion side chain on the Pt skin layer formed on Pt3Co was less positive by ca. 0.2 V than that on Pt, which is a tendency similar to that found for the specific adsorption of ClO4- anions on these electrodes in our recent results obtained by use of the electrochemical quartz crystal microbalance (EQCM).