Varcoe John R, Slade Robert C T, Wright Graham L, Chen Yanling
Department of Chemistry and Microstructural Studies Unit, MSSU, School of Engineering, The University of Surrey, Guildford GU2 7XH, United Kingdom.
J Phys Chem B. 2006 Oct 26;110(42):21041-9. doi: 10.1021/jp064898b.
The performances of H(2)/O(2) metal-cation-free alkaline anion-exchange membrane (AAEM) fuel cells operated with commercially available Au/C and Ag/C cathodes are reported for the first time. Of major significance, the power density obtained with 4 mg cm(-2) Ag/C (60% mass) cathodes was comparable to that obtained with 0.5 mg cm(-2) Pt/C (20% mass) electrodes, whereas the performance when using the same Ag/C cathode in a Nafion-based acidic membrane electrode assembly (MEA) was poor. These initial studies demonstrate that the oxygen reduction electrokinetics are improved when operating Pt/C cathodes at high pH in AAEM-based fuel cells as compared with operation at low pH (in Nafion-based proton-exchange membrane fuel cells). The results of in situ alternating current impedance spectroscopy were core to the assignment of the source of the limited performances of the AAEM-based fuel cells as being the limited supply of water molecules to the cathode reaction sites. Minimizing the thickness of the AAEM improved the performances by facilitating back-transport of water molecules from the anode (where they are generated) to the cathode. The urgent need for development of electrode architectures that are specifically designed for use in AAEM-based fuel cells is highlighted.
首次报道了使用市售Au/C和Ag/C阴极运行的H₂/O₂无金属阳离子碱性阴离子交换膜（AAEM）燃料电池的性能。具有重要意义的是，使用4 mg cm⁻² Ag/C（60%质量）阴极获得的功率密度与使用0.5 mg cm⁻² Pt/C（20%质量）电极获得的功率密度相当，而在基于Nafion的酸性膜电极组件（MEA）中使用相同的Ag/C阴极时性能较差。这些初步研究表明，与在低pH值下运行（在基于Nafion的质子交换膜燃料电池中）相比，在基于AAEM的燃料电池中在高pH值下运行Pt/C阴极时，氧还原动力学得到了改善。原位交流阻抗谱的结果对于确定基于AAEM的燃料电池性能受限的根源在于向阴极反应位点的水分子供应有限至关重要。减小AAEM的厚度通过促进水分子从阳极（水分子产生的地方）向阴极的反向传输而提高了性能。突出了迫切需要开发专门为基于AAEM的燃料电池设计的电极结构。
