Lu Xinyao, Abruña Héctor D
Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States.
ACS Appl Mater Interfaces. 2021 Mar 10;13(9):10979-10986. doi: 10.1021/acsami.0c22738. Epub 2021 Feb 23.
The anion exchange and water dynamics of a phosphonium-based alkaline anion exchange membrane (AAEM) during the methanol oxidation process have been studied with the electrochemical quartz crystal microbalance (EQCM). The viscoelastic effects of the phosphonium-based AAEM in water and the optimal film thickness for EQCM analysis were identified by acoustic impedance analysis. The phosphonium-based AAEM exhibited stronger mechanical toughness in water when compared to a quaternary-ammonium-based membrane that was studied previously. From the simultaneous measurement of the electrochemical response and the frequency changes of the quartz crystal oscillator, water ingress/egress to/from the AAEM film was found to accompany the hydrogen adsorption/desorption, Pt oxidation process, and methanol oxidation process. The in situ study of AAEM films helps illustrate the critical role that water transport plays in electrochemical processes during the operation of anion exchange membrane fuel cells. The generated CO and HCOO, during methanol oxidation, were absorbed into the AAEM film, replacing the OH in the film, as shown by the decrease in frequency after one potential cycle. The exchange of OH by CO and HCOO was found to be reversible. These results provide insights into the anion exchange processes in membranes and emphasize the importance of characterizing the hydrated membranes under electrochemical conditions.
采用电化学石英晶体微天平（EQCM）研究了一种鏻基碱性阴离子交换膜（AAEM）在甲醇氧化过程中的阴离子交换和水动力学。通过声阻抗分析确定了鏻基AAEM在水中的粘弹性效应以及EQCM分析的最佳膜厚度。与之前研究的季铵基膜相比，鏻基AAEM在水中表现出更强的机械韧性。通过同时测量电化学响应和石英晶体振荡器的频率变化，发现水进出AAEM膜伴随着氢吸附/解吸、铂氧化过程和甲醇氧化过程。对AAEM膜的原位研究有助于阐明水传输在阴离子交换膜燃料电池运行过程中的电化学过程中所起的关键作用。甲醇氧化过程中生成的CO和HCOO被吸收到AAEM膜中，取代了膜中的OH，如一个电位循环后频率降低所示。发现CO和HCOO与OH的交换是可逆的。这些结果为膜中的阴离子交换过程提供了见解，并强调了在电化学条件下表征水合膜的重要性。
