A proton conductive silicate-nanoencapsulated polyimide nonwoven as a novel porous substrate for a reinforced sulfonated poly(arylene ether sulfone) composite membrane

Abstract

A novel reinforcing porous substrate that features unprecedented capability of offering proton conductivity is demonstrated for potential use in a reinforced composite proton exchange membrane. The unusual porous substrate (hereinafter, referred to as ''sPI substrate'') is composed of 3trihydroxysilyl propane-1-sulfonic acid (THSPSA)-based silicate coating layers and electrospun polyimide (PI) nonwoven fibers. The THSPSA coating layers bearing sulfonic acid groups endow the sPI substrate with strong affinity for water molecules and also afford appreciable proton conductivity. Another distinctive characteristic of the sPI substrate is the nanoarchitectured structure of the THSPSA coating layers (shell) that encapsulate the PI nonwoven fibers (core). As a result, the coreshell structured sPI substrate maintains a highly porous structure, which plays a crucial role in providing effective proton-conducting channels after the impregnation of a polymer electrolyte (herein, sulfonated poly(arylene ether sulfone) (SPAES)). Notably, owing to the assistance of the protonconductive sPI substrate, the sPI substrate-reinforced SPAES composite membrane presents higher proton conductivity than a PI nonwoven-reinforced SPAES composite membrane under various relative humidity (RH) conditions. This intriguing proton conductivity behavior is discussed based on an in-depth understanding of the unique core-shell structure and functionality of the sPI substrate and, moreover, is quantitatively interpreted by estimating theoretical proton conductivities predicted from series and parallel two-layer models.

Synergistic proton transfer through nanofibrous composite membranes by suitably combining proton carriers from the nanofiber mat and pore-filling matrix

“…7 NFCMs possess approximately a bicontinuous structure within the nanober mat and matrix, which could form long-range proton pathways using the hopping sites. 8 The nanober mats serve as the bone and framework and thus endow the NFCMs with reinforced structural stability. 9 Functional groups on nanobers and the polymer matrix can be independently tuned, and thus benet the control of the proton hopping environment.…”

Nafion-functionalized electrospun poly(vinylidene fluoride) (PVDF) nanofibers for high performance proton exchange membranes in fuel cells

“…As a result, PEMs made with polyelectrolyte nanobers and polyelectrolyte matrix receive research interest with their potential to exhibit enhanced proton conductivity, improved mechanical properties, and high single cell performance. [29][30][31][32][33][34] Moreover, Tamura and Kawakami 35,36 explored the uses of uniaxially-aligned polyelectrolyte nanobers in preparation of composite PEMs. The PEMs showed high proton conductivity in the direction parallel to the aligned bers.…”

Polyimide nonwoven fabric-reinforced, flexible phosphosilicate glass composite membranes for high-temperature/low-humidity proton exchange membrane fuel cells

“…The change in the area (DA) of the samples was estimated using the equation DA (%) ¼ [(A wet À A dry )/A dry ]  100. [18][19][20] The inplane proton conductivities of the PI-GC membrane and SPAES membrane were evaluated with an impedance analyzer (VSP classic, Bio-Logic) using a four probe method over a frequency range of 1  10 À1 to 2  10 5 Hz, [18][19][20][21][22][23] wherein the sample dimension is 3 cm  1 cm (width  length). Prior to measuring proton conductivity, the PI-GC membrane and SPAES membrane were pre-equilibrated in a temperature/humidity control chamber (SH-241, ESPEC) under a given condition of temperature and RH.…”

“…This is similar to the morphology of conventional electrospun polymeric nonwovens. [18][19][20] A salient feature of the PI-GC membrane, as compared to the bulk phosphosilicate glass, is the presence of the PI reinforcing framework. Fig.…”

“…In the present study, as a new strategy to resolve these stringent limitations of typical silicate glass electrolytes, we develop polyimide (PI) nonwoven fabric-reinforced phosphosilicate glass composite membranes (hereinafter, referred to as ''PI-GC membranes''). Here, the PI nonwoven fabric, which is manufactured herein by an electrospinning process, [18][19][20] is employed as a mechanical reinforcing framework endowing the PI-GC membrane with mechanical flexibility and toughness. The phosphosilicate glass, which will act as a three-dimensionally interconnected proton-conducting matrix in the PI-GC membrane, is fabricated directly inside the PI nonwoven framework via in situ sol-gel synthesis of GPTMS/H 3 PO 4 followed by hydrothermal treatment.…”