中文摘要：

在0．4V的恒电位模式下进行了90h的直接甲醇燃料电池（DMFC）稳定性测试，电池性能衰减率为94．63％。采用三电极技术对电极电位进行实时监测。随着电流密度的减小，阴极过电位减小、阳极过电位增加，电池性能的衰减主要来自阳极性能的损失。结合电化学阻抗谱（EIS）及等效电路，对MEA性能的衰减机理进行了解析，并从MEA关键材料的结构变化进行了验证。MEA微结构的变化，导致电池内阻增大了3．19倍，主要表现为阳极扩散层的剥离及微孔层中碳粉的脱落；阳极催化层结构的瓦解导致阳极电化学反应的法拉第阻抗显著增大。

英文摘要：

The stability test of a direct methanol fuel cell （DMFC） was carried out for 90 h at a constant voltage of 0.4 V, the DMFC performance decaying rate was 94.63 %. The three-electrode system was used to real-time detect the anode and cathode potential, the results showed that the cathode overpotential minished along with the decrease of current density, the anode overpoten- tial accumulated along with the decrease of current density. The loss of the anode performance mainly contributed to the degrada- tion of the DMFC performance. The attenuation mechanism of the MEA performance was analyzed by the electrochemical impedance spectroscopy （EIS） and equivalent circuit method, then verified through the structural changes of the key material of MEA. The attenuating mechanism was that the cell internal resistance increased by 3.19 times and the Faraday impedance of the anode electrochemical reaction also significantly increased because of the microstructure changes of the MEA. The variation of MEA was mainly represented by the spin-off of anode diffusion layer from catalyst layer, the drop of carbon of the microporous layers, the disintegration of the anode catalyst layer structure.