## 3 Results and Discussion
This is because the PFAEMs used to evaluate the IEC at BOT and EOT were extracted from a single batch with a size of 12 \(\times\) 12 cm\({}^{2}\). In other words, the BOT and EOT PFAEMs were not identical. Nonetheless, the IEC of the E3-C11 PFAEM showed a significant and noticeable decrease. As shown in Figure 11b,c, the high loss in ion conductivity, as discussed in the alkaline stability section including factors such as the weakness of C-O and C=O bonds in ester groups, the amount of impregnated QA groups, and structural considerations, contributed to the high degradation slope. Moreover, the high loss in ion conductivity in the PFAEM properties correlated with the IEC decrease and the degradation slope under AEMWE operating conditions. As shown in Figure 10a,d, and discussed in the AEMWE performance evaluation section, the OH\({}^{-}\) ion conductivity and IEC of PFAEM directly influence the performance of AEMWE, including \(R_{HFR}\). However, the current density was relatively low due to the high membrane-electrode interfacial resistance, as discussed in \(R_{CTR}\). To address this interfacial resistance, an ionomer layer-coated electrode was designed. The experiments were divided into four configurations: an ionomer layer-coated anode, an ionomer layer-uncoated anode, an ionomer layer-coated cathode, and an ionomer layer-uncoated cathode. Details are provided in Figure 12. As shown in Figure 12a, the AEMWE with both anode and cathode uncoated with the ionomer layer (An \(\times\)/Ca \(\times\)) exhibited the lowest performance, achieving a current density of 285.2 mA cm\({}^{-2}\) at 1.9 V. However, coating the ionomer layer onto the anode and/or cathode improved current density, with sequential increases observed in the order of 397.9 mA cm\({}^{-2}\) (An \(\times\)/Ca O), 428.9 mA cm\({}^{-2}\) (An O/Ca \(\times\)), and 453.2 mA cm\({}^{-2}\) (An O/Ca O). Furthermore, as illustrated in Figure 12b, R\({}_{CTR}\) sequentially decreased in the order of 1010 mOhm\(\cdot\)cm\({}^{2}\) (An \(\times\)/Ca \(\times\)), 508 mOhm\(\cdot\)cm\({}^{2}\) (An \(\times\)/Ca O), 443 mOhm\(\cdot\)cm\({}^{2}\) (An O/Ca \(\times\)), and 392 mOhm\(\cdot\)cm\({}^{2}\) (An O/Ca O) as the ionomer layer was applied. These results demonstrate that when the membrane-electrode interfacial resistance is high, it diminishes the usability of membranes with high ion conductivity, such as E3-C10 PFAEM. This issue can be mitigated by coating the ionomer layer onto the electrode. Figure 10: Performance of PFAEM-based AEMWE: (**a**) I-V polarization curves; (**b**) Tafel plots; (**c**) ohmic overpotentials and \(R_{Total}\) (= \(R_{HFR}\) + \(R_{CTR}\)); (**d**) \(R_{HFR}\) and \(R_{CTR}\) from 1.0 M KOH-fed AEMWE. Figure 11: In situ and ex situ durability of PFAEM-based AEMWE: (**a**) long-term durability of the asymmetric 1.0 M KOH-fed operation at 60 \({}^{\circ}\)C, 500 mA cm\({}^{-2}\) of current density for 100 h; (**b**) BOT and EOT variations in IEC using AEMs of different samples; (**c**) relationship between the loss in ion conductivity of PFAEM and degradation slope in single cell durability evaluation. Figure 12: Performance of E3-C10 PFAEM-based AEMWE using ionomer layer-coated electrode from 1.0 M KOH-fed AEMWE at 60 \({}^{\circ}\)C: (**a**) I–V polarization curves; (**b**) Nyquist plots at 1.7 V.