摘要
以活性炭、纳米碳管为催化层电极材料制备了空气电极 ,测定了稳态极化曲线和交流阻抗。研究发现 ,催化层中纳米碳管的含量对氧的电还原反应有显著影响 ,m(活性炭 )∶ m(纳米碳管 ) =5 0∶ 5 0的空气电极催化活性最高 ,在过电位 ηc 为 40 0～ 60 0 m V时 ,输出电流可达 0 .3～ 0 .5 A/ cm2。EIS测试结果表明 ,不同质量比的活性炭 /纳米碳管空气电极阻抗谱均由 2个半圆弧组成 ,高频区半圆对应欧姆极化阻抗 ,低频区半圆对应氧还原反应的法拉弟阻抗 ,催化层中加入纳米碳管明显减小了电极的欧姆阻抗和法拉第阻抗 ,提高了氧还原反应的催化活性 ,电极过程受氧在薄液膜中的扩散控制 ,单纯纳米碳管形成的催化层多孔结构较容易被电解液渗透 ,界面还存在 Warburg扩散阻抗 ,相应的电催化活性较低。提出了空气电极的等效电路 。
The air electrodes with different mass ratio of active carbon to carbon nanotube as catalyst layer material have been prepared. The electrocatalytic performances for oxygen reduction were evaluated by means of polarization curve and electrochemical impedance spectroscopy(EIS). The results disclosed that carbon nanotube content in the catalyst layer obviously affected the electrocatalytic activity . The air electrode with the mass ratio of active carbon to carbon nanotube of 50∶50 showed the highest electrocatalytic activity, i.e., the output current density reached 300~500 mA/cm 2 when the overpotential was 400~600 mV. The EIS of the as prepared air electrode consisted of two semi circles, in which the high frequency zone was ascribed to the ohmic process and the low frequency zone to the electrochemical kinetic process. The addition of carbon nanotube in the catalyst layer decreased greatly ohmic and kinetic impedance and thereby produced greater enhancement in performances. The mass transport process in the electrode was dominated by the thin film diffusion. The low catalytic activity of the air electrode prepared by the pure carbon nanotube appeared to be a consequence of the penetration of electrolyte into the porous structure. The equivalent circuit of the air electrode was proposed and the simulated kinetics data was analyzed.
出处
《应用化学》
CAS
CSCD
北大核心
2002年第8期759-763,共5页
Chinese Journal of Applied Chemistry
基金
浙江省自然科学基金 (2 9950 2 )
浙江工业大学工程研究中心资助项目
