Constructing dual-interfacial proton-conducting pathways in nanofibrous composite membrane for efficient proton transfer

• CS and SHNTs are mixed and embedded in SPEEK nanofiber mat to prepare NFCMs.
• The dual interfaces donate two distinct pathways for proton transfer in NFCMs.
• Electrostatic interactions enrich and assemble acid–base pairs on the two interfaces.
• NFCMs display reinforced thermal and structural stabilities after SHNTs addition.
• NFCMs achieve enhanced conductivities under hydrated and anhydrous conditions.

To achieve high proton conduction ability, we report here a novel and facile strategy to construct dual-interfacial proton-conducting pathways in the platform of nanofibrous composite membranes (NFCMs) by mixing sulfonated halloysite nanotubes (SHNTs) with chitosan (CS) matrix and then incorporating them into the pores of sulfonated poly (ether ether ketone) (SPEEK) nanofiber mat. In such a way, two distinct interfacial pathways are created at SPEEK/CS and CS/SHNTs interfaces, on which ordered acid–base pairs (–SO3-…+H3N–) are formed. And the strong electrostatic attractions endow NFCMs with enhanced structural stabilities by regulating polymer chain mobility and stacking. The dual-interfacial proton-conducting pathways confer ultrafast proton conduction on NFCM under both hydrated and anhydrous conductions via Grotthuss mechanism. Especially, CS/SPNF/SHNTs-5 achieves remarkable conductivities of 117.7 mS cm−1 under 90 °C and 100% RH, and 19.95 mS cm−1 at 100 °C and 0% RH. Benefiting from the structural stability, the as-prepared NFCMs display excellent conduction stability for promising long-term operation. Moreover, to verify the universality of this nanostructured-transfer pathway, another kind of NFCM is fabricated using polydopamine modified nanofiber mat bearing numerous polydopamine nanoparticles. SPEEK is chosen as polymer matrix and incorporated into the mat to prepare the NFCMs, which also display expected efficient proton transfer behaviors.

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