Proton Conductivity through Polybenzimidazole Composite Membranes Containing Silica Nanofiber Mats

Abstract

The quest for sustainable and more efficient energy-converting devices has been the focus of researchers′ efforts in the past decades. In this study, SiO2 nanofiber mats were fabricated through an electrospinning process and later functionalized using silane chemistry to introduce different polar groups OH (neutral), SO3H (acidic) and NH2 (basic). The modified nanofiber mats were embedded in PBI to fabricate mixed matrix membranes. The incorporation of these nanofiber mats in the PBI matrix showed an improvement in the chemical and thermal stability of the composite membranes. Proton conduction measurements show that PBI composite membranes containing nanofiber mats with basic groups showed higher proton conductivities, reaching values as high as 4 mS·cm−1 at 200 C.

Recent Progress in the Development of Composite Membranes Based on Polybenzimidazole for High Temperature Proton Exchange Membrane (PEM) Fuel Cell Applications

“…In a recent publication of the group of Compañ, SiO 2 nanofiber mats were used as fillers in the preparation of composite PBI membranes for high temperature PEMFC applications [ 76 ]. In this work, SiO 2 nanofibers were fabricated through an electrospinning process and later functionalized using silane chemistry to introduce different polar groups, namely, −OH (neutral), −SO 3 H (acidic), and −NH 2 (basic).…”

“…Our group has also contributed to the field of nanofiber materials through the preparation of PBI composite membranes containing SiO 2 nanofiber mats [ 76 ]. The nanofiber materials were fabricated via the electrospinning process and later functionalized with terminal neutral, acidic, and basic groups using silane chemistry.…”

“… FE-SEM images of SiO 2 nanofibers and temperature dependence of composite PBI membranes with neutral (PBI@SiNF), basic (PBI@SiNF–NH 2 ), and acidic groups (PBI@SiNF–SO 3 H) [ 76 ]. …”

Synthesis and Properties of Phosphoric-Acid-Doped Polybenzimidazole with Hyperbranched Cross-Linkers Decorated with Imidazolium Groups as High-Temperature Proton Exchange Membranes

“…The proton conductivity of OPBI reached 0.043 S cm −1 at 160 °C (Table 2). For ImOPBI-5, the proton conductivity reached 0.089 S cm −1 at 160 °C due to the increase in the phosphoric acid doping rate, which was higher or comparable to that based on PBI membranes [35][36][37]. With the increase in the cross-linking degree, although the phosphoric acid content of ImOPBI-10 and ImOPBI-15 decreased, more imidazolium groups were introduced into the membranes, which not only acted as a Bronsted base but also promoted phosphoric acid ionization to form ion pairs with phosphoric acid (Im + •••H 2PO4• (H3PO4)n), providing transfer sites for proton transfer.…”

Novel Polymeric Composite TPPS/s-PEEK Membranes for Low Relative Humidity PEFC

“…In order to maintain an adequate proton conductivity and preserve the mechanical properties, under low RH conditions, hygroscopic and/or proton conductor fillers are introduced into the membrane, as well as blending with other polymers, with the aim of maintaining the appropriate amount of water for proton conduction [11][12][13]. The fillers generally used for this purpose are composed of ceramic oxides or functionalized oxides, polymers with specific functional groups and organic compounds [14][15][16][17][18][19][20][21][22][23][24]. In this framework, the insertion of compounds or polymers containing nitrogenous groups, due to the ability of specific interactions/bonding with the sulfonic groups, is considered fruitful to reduce the swelling effect at high temperature and to improve the proton conductivity [25][26][27][28][29][30].…”