The current density (i) - cell voltage (V) characteristics were measured using various cell set-ups In the cell set-ups, a commercial AEM (A201, Tokuyama) was applied for the membrane electrolyte, and commercially available electrocatalyst was used for hydrogen (cathode) and oxygen (anode) evolution, namely, 4030 and 3030 (Acta SpA), respectively . Cathode catalyst layers (CLs) were commonly prepared by catalyst coating membrane (CCM) method using commercial anion exchange ionomer (AS-4, Tokuyama) as a binder. As for anode, two different arrangements for CL configuration were adopted, namely, CCM and CCS. In the fabrication of CCS, polytetrafluoroethylene (PTFE) was used as a binder. In order to examine the stability of electrode structure, the series of i-V measurement was repeated in 2 days.
The observed i-V and i-R_cell characteristics using different cell set-ups are shown in Figure 1. In EL1 cell, the both electrodes were fabricated by CCM. As shown in Fig. 1 (a), the i-V performance of EL1 in 2nd day was definitely degraded from that in 1st day. In particular, the difference in V was relatively large even in small i range (<100 mA cm-2), though the difference in R_cell was negligible. It means that the degradation was mainly caused by the increase of activation overpotential related to catalyst performance. In the case of EL2 cell, CCS was applied for the anode CL, while the cathode CL was fabricated by the CCM method. As shown in Fig. 1 (b), the degradation in 2nd day was significantly decreased. It was clearly suggested that, for the anode, CLs fabricated by CCS must be much stable rather than that of CCM.
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