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The application of vanadium redox flow batteries (VRFBs) has encountered challenges because the most commonly used commercial membrane (perfluorinated sulfonic acid, PFSA) has severe vanadium ion permeation, which yields poor stability of the battery. Herein, a PFSA‐based hybrid membrane with a sandwich structure created using a reinforced polytetrafluoroethylene thin layer with hydrophilic nanohybrid fillers is developed. The tungsten trioxide (WO3) nanoparticles are in situ grown on the surface of graphene oxide (GO) nanosheets to overcome the electrostatic effect, and to enhance the hydrophilicity and dispersibility of GO nanosheets, which is embedded in the PFSA matrix to act as a "barrier" to reduce vanadium ions permeation. In addition, these hydrophilic WO3 nanoparticles on GO nanosheets surface serve as proton active sites to facilitate proton transportation. As a result, at 120 cm−2, the cell of the hybrid membrane displays high Coulombic efficiency (over 98.1%) and high energy efficiency (up to 88.9%), better than the commercial Nafion 212 membrane at the same condition. These performances indicate the proposed hybrid membrane is applicable for VRFB application. Also, this design method of the membrane can be extended to other fields including water treatments and fuel cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A PTFE@PFSA/Functionalized-SiC membrane with sandwich structure is fabricated. • The hybrid membrane has low vanadium ion permeation and high proton conductivity. • A VRFB cell with the hybrid membrane shows high efficiency and cyclic stability. As a key component of vanadium redox flow battery (VRFB), ion exchange membrane determines the performance of VRFB, wherein commercial membrane (such as Nafion) exacerbate problems including high permeability of vanadium ions and poor cyclic stability. In this study, a low vanadium ion permeation hybrid membrane is developed by dispersing functionalized silicon carbide nanowires in perfluorinated sulfonic acid (PFSA) matrix and sandwiching an ultrathin porous polytetrafluoroethylene (PTFE) layer. This hybrid membrane greatly improves the performance of VRFB cell exhibiting good Coulombic efficiency (up to 96.2%) and high energy efficiency (up to 87.1%) at 120 mA cm−2, contrasted with the Nafion 212 membrane (91.3% and 79.8%). Furthermore, a single cell with the hybrid membrane possesses ultra-stable cyclicity (1000 cycles, over 233.4 h). This can be assigned to the unique structure of the membrane in which the functionalized nanowires are uniformly dispersed in PFSA matrix to sandwich an ultra-thin PTFE layer to block or lengthen the diffusion paths of vanadium ions, while the functionalized groups on the surface of the rigid nanowires facilitate protons transportation. This strategy of reshaping membrane may serve in relative fields including proton exchange membrane fuel cells and water treatment. [ABSTRACT FROM AUTHOR]