Fig. 3. Dynamic contact angle measurements with a 1 M KOH solution on a (A) pure H23C6 GDL, (B) 5 wt% CST containing Cu based GDE and a (C) 30 wt% CST containing Cu based GDE. Cross-sectional SEM EDX images of the catalyst layer and the microporous layer of the GDL, showing the structure, the copper and potassium content of a (D) CST-free Cu GDE and a (E) 5 wt% CST containing Cu GDE.