直接甲醇燃料电池动态行为的交流阻抗研究

Research of AC Impedance of Dynamic Behavior of Direct Methanol Fuel Cell

采用交流阻抗法(EIS)研究了直接甲醇燃料电池(DMFC)放电状态下的动态电化学行为及内部作用机理.通过L1R1[QR2(L2R3)]形式的等效电路对其阻抗图谱进行了较好的模拟解析,研究结果表明,高频电感(L1)相关于EIS的测量过程;系统电阻(R1)和电荷转移电阻(R2)随工作电流的升高均呈下降趋势,但传质状况对其具有一定干扰;低频电感(L2)和低频电阻(R3)随电流的升高均逐渐降低,这共同反映出阳极甲醇的电氧化行为;电极反应驱动力和内部传质共同决定常相位角元件Q的变化规律,随着放电电流的升高,电池内部表现出了由理想电容到浓差极化的中间过渡过程.

Electrochemical Impedance Spectrum （EIS） was employed to investigate the dynamic behavior and interior mechanism of direct methanol fuel cell （ DMFC ） in working states. The spectrums were simulated through the equivalent circuit of LtRt [ QR2 （L2R3 ） ], and the results show that the high inductance L1 was only related to the EIS measurement process. Meanwhile, the system resistance R1 and charge transfer resistance R2 was shown to decrease gradually but was affected by mass transfer at high discharging current. Both the low inductance L2 and low frequency resistance R3 in circuit reflected the adsorption/desorption balance of intermediate species originating form methanol oxidation reaction, which decreased with the discharge current increasing. The constant phase elements（CPE） Q in this circuit was mainly influenced by the driving forces of both reactions and mass transfer, and indicated that there existed a transition process from ideal capacitance to the charge transfer with the discharging current increasing.