Constructing High-Density Hydrogen Bonding Networks via Introducing the Bipyridine Group for High-Performance Fuel Cell Proton Exchange Membranes

Abstract

Constructing high-density hydrogen bonding networks is crucial to improve the proton conductivity of proton exchange membranes (PEMs) and the single-cell output power of high-temperature fuel cells (HTFCs). In this work, a series of benzimidazole polymers containing a pyridine group in the backbone are successfully synthesized via copolymerization. The high-density hydrogen network is constructed via blending the polyether polybenzimidazole (OPBI) with the bipyridine polybenzimidazole copolymer, and the 1,3,5-triglycidyl isocyanurate that contains nitrogen atoms and hydroxyl groups is used as a cross-linking agent. As a result, the proton conductivity and the output power density of the single cell are significantly enhanced by the high-density hydrogen bonding network. The single-cell performance of 693 mW cm–2 is achieved in the cross-linked OPBI/copolymer blend membranes containing pyridine group under a saturated phosphoric acid (PA) adsorption (284%). Even under the low PA uptake (178%), the proton conductivity (0.050 S cm–1) is 2.1 times that of the OPBI membrane (0.024 S cm–1), and the output power density of the single-cell performance (501 mW cm–2) is 1.4 times that of the OPBI membrane (358 mW cm–2). The results demonstrate that introducing nitrogen sites into polybenzimidazole cross-linked membranes is an effective strategy for preparing high-performance fuel cell PEMs.

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

“…18 Effective proton hopping among accumulated functional groups was also experimentally and computationally revealed by Yamaguchi et al 19,20 Similar studies utilizing high-density hydrogen-bonding networks for proton conduction at high temperatures and low humidity have been reported by several groups. 21,22 These approaches offer promising prospects for proton conduction at high temperatures and low humidity; however, reliable utilization of PEMs at high humidity above 80% RH is necessary because future PEFC will be operated not only under high temperature and low humidity conditions (e.g., 120 °C, 30% RH) but also under relatively low temperature and high humidity conditions (e.g., 80 °C, 80% RH) due to generation of a copious amount of water by the electrochemical reaction at high current density fuel cell operation. 9 In our previous study, we developed electrolyte membranes with high conductivity at high temperatures and low humidity by doping PA into blend membranes consisting of sulfonated polyimide (SPI) and polybenzimidazole (PBI).…”

Porphyrin Helical Nanochannel‐Assembled Polybenzimidazole Membranes Doped with Phosphoric Acid for Fuel Cells Operating in a Temperature Range of 25–200 °C

“…[36] Synthesis of the Pyridine-Based Polybenzimidazole: As shown in Scheme S1b (Supporting Information), and in the Synthesis of the Branch Pyridine Based Polybenzimidazole, as per a literature on the reported PPA process by using a dehydration-condensation reaction between 4,4′-oxybisbenzoic acid, 2,6-pyridinedicarboxylic acid and 3,3′-diaminobenzidine. [8,37] In a detailed procedure, under a N 2 atmosphere, 100.00 g of PPA was introduced into a three-necked flask and stirred at 140 °C for 0.5 h. Subsequently, 1.18 g of 3,3′-diaminobenzidine (5.5 mmol) was added, and after complete dissolution, 0.83 g of 2,6-pyridinedicarboxylic acid (5 mmol) was introduced and stirred for 4 h. The mixture was then heated to 190 °C and maintained for a minimum of 2 h. Afterward, the mixture was cooled to 140 °C, and 0.96 g of 3,3′-diaminobenzidine (4.5 mmol) and 1.32 g of 4,4′-oxybis benzoic acid (5.1 mmol) were added and stirred for 4 h. The temperature was subsequently raised to 200 °C, and the mixture was stirred for ≈6 h. After a slight cooling, a viscous solution was obtained and then poured into a saturated NaHCO 3 solution. Some fiber-like solid was obtained.…”

“…Even at a low PA absorption rate (178%), the proton conductivity (0.050 S cm −1 ) is 2.1 times that of the poly [2,2′‐(p‐oxydiphenylene)−5,5′‐benzimidazole (OPBI) membrane (0.024 S cm −1 ), and the output power density (501 mW cm −2 ) of the single cell is 1.4 times that of the OPBI membrane (358 mW cm −2 ). [ 8 ] Recently, branched polymers have been studied in the field of HT‐PEMFCs. [ 9 ] Branched PBI has a unique 3D structure, forming many open and accessible cavities within the membrane, increasing the doping level of PA and thus helping to improve proton conductivity.…”

Enhancing Performance and Stability of High-Temperature Proton Exchange Membranes through Multiwalled Carbon Nanotube Incorporation into Self-Cross-Linked Fluorenone-Containing Polybenzimidazole

“…High-temperature proton exchange membrane (HT-PEM) fuel cells (HT-PEMFCs), operating above 120 °C, have garnered extensive research attention due to their superior carbon monoxide (CO) tolerance and simplified hydrothermal management. − The PEM plays a pivotal role in HT-PEMFCs, employing various polymers for this purpose. ,− Notably, sulfonated polyetheretherketone, − polybenzimidazole (PBI), − sulfonated polysulfone, and poly­(vinyl alcohol) (PVA) are among the majorly studied PEMs. Phosphoric acid (PA)-doped PBI membranes stand out as a particularly promising system for HT-PEMFCs, owing to their remarkable thermal stability, PA stability, aging resistance, and modifiable polymer backbone. − The proton conductivity of PA-doped PBI membranes directly correlates with their PA content, influencing proton transport through PA hydrogen-bond networks.…”