材料期刊网

在提高大电流密度下工作时空气电极的寿命.以活性炭、乙炔黑、PTFE乳液为原料,用辊压法制备空气电极,并将其置于惰性气氛(N2,CO2)中烧结.用TG-DTA研究电极材料的热行为,用扫描电子显微镜(SEM)、压汞分析、透气性测试等方法表征空气电极的孔结构,用稳态极化曲线法测定电极的电化学性能.研究了烧结影响空气电极的微孔结构及其稳定性的机理.试验结果表明,烧结工艺能极大地提高空气电极的寿命和性能,这可归因于烧结使PTFE与电极材料中的炭粒子凝结为一体,保持了三相界面的稳定,烧结过程中PTFE中的表面活性剂和低分子量的聚合物分解,起到造孔的作用,增加了电极的三相反应表面积.试验结果有助于优化电极的制备工艺.

This paper is aimed at increasing the lifetime of the gas diffusion electrode which loads at higher current densities. The gas diffusion electrode was prepared from active carbon, acetylene black and PTFE suspension by rolling and sintering in inert gases (N2 or CO2). The effects of sintering procedure on the microstructure and long-term stability of gas diffusion electrode for oxygen reduction in alkaline electrolyte without application of electrocatalysts were examined. The thermal behavior of the electrode materials was investigated by TG-DTA. The surface morphology of the gas diffusion electrode was characterized by SEM, Hg-porosimetry and permeation. The electrochemical behavior of electrode was determined by means of polarization curves in alkaline electrolyte. Experimental results reveal that the sintering procedure has a significant effect on the long-term stability of the gas diffusion electrode. The increase in the lifetime of the gas diffusion electrode may be attributed to the sintering procedure that leads to the coagulation between particle of both PTFE and carbon, which further results in the stability of the microstructure of gas diffusion electrode. Furthermore, small molecular polymer and disperser in polytetrafluoroethylene (PTFE) suspension can be decomposed to serve as pore former during heating process, resulting in the even pore distribution and higher accessibility of the surface areas to the reactants and products. The results contribute to optimization of the electrode manufacturing technology as well.