Sulfonated Poly(ether ether ketone) Hybrid Membranes with Amphoteric Graphene Oxide Nanosheets as Interfacial Reinforcement for Vanadium Redox Flow Battery

Abstract

Sulfonated poly(ether ether ketone) (SPEEK) hybrid membranes are prepared by incorporating 2,2′-benzidinedisulfonic acid-functionalized amphoteric graphene oxide (GO-BDSA) nanosheets. The optimized membrane permeability and ion selectivity greatly regulate the vanadium flow redox battery (VRFB) performance in terms of the formed interfacial action. At a 1 wt % loading of GO-BDSA nanosheets, proton conductivity and ion selectivity of SPEEK/GO-BDSA-1 reach a maximum value such as 30.7 mS cm–1 and 43.3 × 103 S min cm–3, respectively. As compared with the self-discharge time of SPEEK (38 h) and Nafion 117 (33.5 h), SPEEK/GO-BDSA-1 hybrid membrane shows a longer one, 95.3 h. In the meantime, higher voltage efficiency (VE, 92%) and energy efficiency (EE, 85%) than those of SPEEK (VE, 87% and EE, 82%) and Nafion 117 (VE, 89% and EE, 84%) are confirmed at 50 mA·cm–2. The structure stability and durability of SPEEK/GO-BDSA-1 hybrid membrane are supposed after 250-time charge–discharge test, which is ascribed to the interaction of GO-BDSA nanosheets and SPEEK matrix. So, SPEEK/GO-BDSA hybrid membranes demonstrate a promising prospect for VRFB as the proton exchange membrane.