A series of sulfonated poly(ether ether ketone) (SPEEK) and graphene oxide (GO) blend membranes were prepared with various mixing mass ratios.The water uptake

ion exchange capacity

proton conductivity

vanadium ion permeability

mechanical properties and chemical stability were measured.The blend membranes were characterized by FTIR

SEM and TG.The blend membranes exhibit higher water uptake and ion exchange capacity and lower vanadium ion permeability than Nafion115 membranes

the ion exchange capacity decreases with the increase of GO content.The VO2+ permeability of the blend membranes decreased

while mechanical properties increased with increasing GO content.Random embedding of GO in the membranes can block the transport of vanadium ions effectively

resulting in vanadium ion permeability of the blend membranes decreased obviously.In VRB single cell test

the blend membranes showed higher energy efficiency (EE) compared with Nafion115 membrane

the EE of S/GO-2 (GO

2 wt%) blend membrane was 80% which increased by 9% compared to that with Nafion115.The S/GO blend membranes showed stable performance up to 100 cycles test.The experimental results indicate that the S/GO blend membranes show favorable development prospects for VRB.