固体聚合物电解池膜电极优化研究

Optimization of membrane electrode assembly for SPE water electrolysers

采用催化剂直接涂膜(CCM)方法制备膜电极(MEA),研究阴极和阳极催化层中使用不同催化剂活性组分担载量对膜电极性能的影响。采用电化学阻抗谱(EIS)分析MEA的电化学特性。研究结果表明:阳极催化层中,随着Ir担载量的增加,在相同电流密度条件下,电解池的极化电压下降,当Ir担载量增加到2.5 mg/cm^2以上,极化电压趋于稳定;阴极催化层中,随着Pt担载量的增加,在相同电流密度条件下,电解池的极化电压下降,当Pt担载量增加到0.5 mg/cm^2以上,极化电压下降不明显,趋于稳定。随着电极催化层活性组分担载量的增加,MEA的欧姆阻抗R?和电荷传递阻抗RCT的减小。对于阴极催化层,当Pt/C催化层的催化剂担载量过多时,由于传质和电荷传递阻力显著增加,导致MEA的R?和RCT增大。阳极催化层Ir的最佳担载量为2.5 mg/cm^2,阴极催化层Pt的最佳担载量为0.5 mg/cm^2。

The membrane electrode assemblies（MEA） were fabricated by the catalyst coated membranes（CCM） where thin and porous catalyst layers were preferably deposited on both sides of the membrane. The different catalyst loadings of both cathode and anode were investigated to develop high performance MEA for solid polymer electrolyte（SPE） water electrolysis. The electrochemical property of MEA was analyzed by electrochemistry impedance spectroscopy（EIS）. The results show that the polarization voltage decreases in the same current density with the increase of catalyst loading. However, the improvement of voltage is insensitive when catalyst loading is up to a threshold value. The threshold of Ir is 2.5 mg/cm^2 for anode and Pt is 0.5 mg/cm^2 for cathode, respectively. RCT and R？ decrease with the increase of the catalyst loading. Excess catalyst loading leads to the increase of mass and charge transfer resistance for cathode, which results in the increase of R？ and RCT of bad MEA. The optimal loading for anode（Ir） and cathode（Pt） is 2.5 mg/cm^2 and 0.5 mg/cm^2, respectively.