Proton-conducting nanofiber hybrid membranes (PC-NFHMs) as promising candidates, are widely used for proton exchange membrane fuel cells (PEMFCs), combining the properties and some synergism from interactions between nanofibers and the polymer matrix. The PC-NFHMs possess superior characteristics compared to individual ion-conducting polymeric membranes or free-standing electrolyte inorganic films. Herein, this critical review presents the progress of PC-NFHMs, with specific focus on the combinations of multifunctional nanofibers and emerging proton transfer carriers, such as metal organic frameworks (MOFs), porous organic cages (POCs), polyhedral oligomeric silsesquioxanes (POSSs), amino acids (AAs), etc. The unique properties and performance of the different types of multifunctional nanofibers and their derivatives are described with respect to their use as PC-NFHMs. Besides, relevant characterization studies including small angle X-ray scattering (SAXS), nuclear magnetic resonance (¹H-NMR), and molecular dynamics calculation (MDC), have been briefly summarized to understand proton-conducting mechanisms (Vehicle and Grotthuss mechanisms) in electrolyte membranes. These systematic discussions and proposed directions can trigger thoughts and provide ways to reasonably design PC-NFHMs for PEMFCs in the near future.

In this study, a new type of modified Nafion membrane containing sulfonated poly(ether ether ketone) (SPEEK) nanofibers was fabricated for proton exchange membrane fuel cells. The solution blowing method was used for fabrication of SPEEK nanofibers, which were impregnated into Nafion solution to form pore-filled composite membranes with different contents of SPEEK nanofibers. The performance of the composite membranes as proton exchange membranes was investigated and compared with Nafion 117. The results showed that the introduction of SPEEK nanofibers into the Nafion matrix significantly improved its thermal stability, proton conductivity, swelling rate and selectivity. The maximum value of the proton conductivity of 0.09 S cm⁻¹ was obtained when the nanofiber content was 10 wt% at 20 °C and 100% RH, higher than that for Nafion 117 (0.083 S cm⁻¹). It is indicated that solution blown nanofibers are a kind of promising filler material for enhancing the performance of Nafion membranes, and the composite membrane containing SPEEK nanofibers can be considered as a novel proton exchange membrane for fuel cell applications.

In this work, nylon 6 core–chitosan/poly(vinyl alcohol) (PVA) shell hydrogel nanofibers (NCNFs) were fabricated by coaxial solution blowing. The hydrogel fibers were 80–650 nm in diameter with smooth surfaces. These fibers were distributed randomly and formed three-dimensional mats. Cibacron Blue F3GA (CB) was then immobilized onto the membrane surfaces for subsequent protein affinity adsorption. The amount of PVA in the shell greatly influenced CB content and bovine serum albumin (BSA) adsorption. The highest BSA adsorption capacity achieved by the NCNF membranes with immobilized CB was 379.43 mg g⁻¹. The results showed that NCNFs combine the large capacity of hydrogels and the high flux of nanofibrous mats for affinity adsorption.