Hybrid proton exchange membrane of sulfonated poly(ether ether ketone) containing polydopamine-coated carbon nanotubes loaded phosphotungstic acid for vanadium redox flow battery

A hybrid membrane of sulfonated poly(ether ether ketone)/polydopamine-coated carbon nanotubes loaded phosphotungstic acid (S/DCNTs-HPW) is proposed for vanadium redox flow battery (VRFB). With the DCNTsHPW nanofillers as the proton donor and acceptor, a high proton conductivity and low vanadium ions permeability of the S/DCNTs-HPW hybrid membranes is demonstrated owing to the formed acid-base interaction. Specifically, S/DCNTs-HPW-1 gives higher ion selectivity (25.4 x 10(3) S min cm(-3)) than that of pristine SPEEK (4.3 x 10(3) S min cm(-3)) and Nafion 117 (4.0 x 10(3) S min cm(-3)). Cell utilizing S/DCNTs-HPW-1 reveals excellent coulombic efficiency (98.2?99.4%) and energy efficiency (89.5-69.0%) under the current density of 50-160 mA cm(-2), and a 34.5% charge capacity retention under 100 cycles is achieved based on the excellent membrane structure and chemical stability. The S/DCNTs-HPW-1 membrane shows a self-discharge time of 576 h, which is longer than that of the Nafion 117 membrane (23 h). Thus, the S/DCNTs-HPW hybrid membranes are suggested for potential use as alternative PEMs in the VRFB system.

Automated summary

The hybrid membrane of Sulfonated Poly(ether ether ketone)/Polydopamine-coated Carbon Nanotubes loaded Phosphotungstic Acid (S/DCNTs-HPW) shows high ion selectivity and excellent charge capacity retention, making it a potential alternative for Proton Exchange Membranes in Vanadium Redox Flow Battery systems.