“…From 40 mA cm À2 to 100 mA cm À2 , the EE values (87.5%, 85.7%, 83.5%, 80.2%, at 40, 60, 80, 100 mA cm À2 , respectively) of cell with PyPPSU-2 membrane was higher than that (85.7%, 83.5%, 80.0%, 77.2% at 40, 60, 80, 100 mA cm À2 , respectively) of cell with Nafion 117 membrane. Furthermore, at a current density of 80 mA cm À2 the cell with PyPPSU-2 membrane showed an EE of 83.5%, which was comparable with the EE (84%) reported by Zhang et al [26] and EE (83.6%) by Zhang et al [28] under the similar test condition (80 mA cm À2 , 1.5 M V 2þ /V 3þ and 1.5 M VO 2þ /VO 2 þ in 3.0 M H 2 SO 4 ). Additionally, the cell with PyPPSU-2 showed high EE of 80.2% even at high current density of 100 mA cm À2 , which was higher than that of cell with Nafion 117 membrane (77.2%) under the same test condition.…”