Development of Blend Nanofiber Composite Polymer Electrolyte Membranes with Dual Proton Conductive Mechanism and High Stability for Next-Generation Fuel Cells

Abstract

Blend polymer nanofibers (BNF), consisting of sulfonated polyimide and polybenzimidazole blends doped with phytic acid, were fabricated and composed with Nafion to give BNF composite membranes for polymer electrolyte fuel cells. The BNF composite membrane possessed high mechanical and chemical stabilities and low gas permeability. In addition, the BNF composite membrane showed higher proton conductivity than the commercial Nafion NR211 membrane, not only at low temperatures but also at high temperatures above 100 °C and low relative humidity (ca. 10% RH). The proton conduction mechanism in the BNF composite membranes was examined and revealed that proton hopping conduction occurred besides the vehicle mechanism in the BNF composite membranes. The BNF composite membrane provided improved fuel cell performances compared to the cell using the conventional Nafion NR211 membrane at high humidity, low humidity, and high temperature/low humidity, suggesting the potential of BNF composite membranes for next-generation fuel cells.

All-Perfluorosulfonated-Ionomer Composite Membranes Containing Blow-Spun Fibers: Effect of a Thin Fiber Framework on Proton Conductivity and Mechanical Properties

“…The PFSA thin fiber composite membrane outperformed the pristine PFSA one over the entire current density range for all the temperature conditions: the Ohmic polarization of the PFSA thin fiber composite membrane was improved compared with the pristine PFSA one. The obtained peak power density ( P max ) values for the PFSA thin fiber composite membrane (1324, 704, and 300 mW cm –2 at 80, 100, and 120 °C, respectively) were better than those of the pristine PFSA membrane (1161, 600, and 253 mW cm –2 at 80, 100, and 120 °C, respectively); and compared with the previously reported PEFC performances, 15 , 29 , 40 − 44 particularly for the high-temperature low-humidity condition at 120 °C and ∼25% RH ( Table S1 ).…”

“…This trend is consistent with the proton conductivity through the membranes described above (Figure ). To discuss the effect of PFSA thin fiber webs (i.e., interconnected thin fiber framework) in the composite membranes in detail, we estimated the proton conductivity of the thin fiber webs (σ fiber ) in the composite membranes from the R ohm values obtained from EIS measurements using a first-approximated parallel model as follows σ normalm normale normalm normalb = ϕ normalf normali normalb normale normalr σ normalf normali normalb normale normalr + ϕ normalm normala normalt normalr normali normalx σ normalm normala normalt normalr normali normalx where σ memb , ϕ fiber , σ matrix , and ϕ matrix represent the proton conductivity of the composite membrane, the volume fraction of thin fiber web (15 vol %, we assume that the volume fraction equals to the weight one of thin fiber web because all components of the composite membrane is Aquivion), proton conductivity of the matrix (we assume that it equals to that of the pristine PFSA membrane), and volume fraction of matrix (85 vol %). The estimated proton conductivity of PFSA thin fiber webs in the composite membranes was higher than those of the matrix, particularly during FC operation (Table ), indicating the substantial effect of PFSA thin fiber webs on the proton conductivity during FC operation.…”

“…Conventional PEMs that are used in commercial PEFCs are the PFSA ionomer membranes reinforced with porous expanded PTFE (such as Gore-Select and Nafion XL). ,, Recently, highly porous electrospun poly­(vinylidene fluoride) (PVDF) nanofibers were used as the reinforcement to improve the dimensional stability of PFSA ionomer membranes. , In addition, ion-conductive nanofibers can increase ionic transport pathways in a polymer matrix compared with ion-insulating nanofibers such as PVDF nanofibers . In line with this scenario, there are many reports on preparation of composite PEMs containing ion-conductive nanofibers for the electrochemical devices including fuel cells. − The ion-conductive three-dimensional (3D) nanofiber framework can improve the electrochemical properties of the composites and mechanically reinforce the polymer matrix. − …”

“… 9 − 12 The ion-conductive three-dimensional (3D) nanofiber framework can improve the electrochemical properties of the composites and mechanically reinforce the polymer matrix. 13 − 15 …”

Proton‐Conducting Polymers: Key to Next‐Generation Fuel Cells, Electrolyzers, Batteries, Actuators, and Sensors

“…Suzuki et al specifically investigated blend nanofibers (BNFs) produced by electrospinning and composed of sulfonated polyimide and polybenzimidazole blends doped with phytic acid (Figure 2a). [20] In fact, phytic acid (Phy) has six phosphoric acid groups in one molecule. They fabricated BNF by modifying the surface of PBI NFs with Phy to form multipoint acidÀ base interactions [21] through multiple phosphoric acid groups and benzimidazole rings.…”