Achieving over 1,000 mW cm⁻² Power Density Based on Locally High‐Density Cross‐Linked Polybenzimidazole Membrane Containing Pillar[5]arene Bearing Multiple Alkyl Bromide as a Cross‐Linker

Abstract

Cross-linking is widely accepted as an effective method to improve the mechanical strength and durability of phosphoric acid (PA) doped polybenzimidazole (PBI) membranes. However, the cross-linked membranes generally exhibit compromised overall performance since their compact network structures decrease the free volumes of membranes, leading to poor proton conductivity. In this study, a locally high-density cross-linked polybenzimidazole network based on pillar[5]arene bearing multiple alkyl bromide is constructed for the first time to achieve high proton conductivity, desired mechanical properties, and excellent fuel cell performance. The pillar[5]arene-crosslinked network considerably enhances the mechanical strength of membrane (14.6 MPa), particularly with high PA uptake, and provides loose PBI chain segment packing to retain PA (315.9%). Surprisingly, the pillar[5]arene-crosslinked PBI membrane displays a high-power density of 1,084.1 mW cm −2 at 180 °C and 0.6 mg cm −2 Pt loading without backpressure and humidification, that is the highest value reported in cross-linked membranes for high-temperature proton exchange membrane fuel cells.

Acid-Doped Pyridine-Based Polybenzimidazole as a Positive Triboelectric Material with Superior Charge Retention Capability

“…Meanwhile, the −NH– groups also confer adsorption capabilities of PBI to various ions, which has been applied in fuel cells, − gas separation, − flow batteries, − and so on. − Here, an ion chimera strategy is proposed by embedding and doping various ions into PBI to enhance the charge retention capability of PBI films. The benzimidazole groups in PBI chains have base functionalities and can embed and react with protic acids such as H 3 PO 4 , H 2 SO 4 , and HCl to form a protic polybenzimidazolium (Figure a).…”

Double cross-linked 3D layered PBI proton exchange membranes for stable fuel cell performance above 200 °C

“…d Optimization strategies diagram of this study. e Comparative analysis of proton conductivity versus gel content of the reported PBI membranes 14 , 35 – 37 . f Comparison of this work with reported PEMs in conductivity 38 – 45 .…”

“…To address above trade-off issue, Wang et al used a pillar[5]arene to prepare a proton exchange membrane with heterogeneous cross-linking arrangement, resulting in improved mechanical strength (14.6 MPa) and PA retention. The resulted PEM with a proton conductivity of 0.240 S cm −1 at 180 °C, achieved minimal voltage decay of 0.04 mV h −1 in fuel cell operated over a 200 h at 160 °C 14 .…”

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

“…While higher PA doping levels enhance conductivity, excessive doping can compromise membrane mechanical strength due to loose polymer chain accumu- lation. 7,27,28 Cross-linked PBI emerges as a promising HT-PEM, demonstrating excellent chemical and thermal stability and outstanding mechanical properties at high temperatures. 3,29 For instance, Wang et al 30 presented a novel approach involving cross-linked porous PBI membranes with notable proton conductivity (0.048 S cm −1 ) and tensile strength (12.21 MPa).…”

“…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. While higher PA doping levels enhance conductivity, excessive doping can compromise membrane mechanical strength due to loose polymer chain accumulation. ,, Cross-linked PBI emerges as a promising HT-PEM, demonstrating excellent chemical and thermal stability and outstanding mechanical properties at high temperatures. , For instance, Wang et al presented a novel approach involving cross-linked porous PBI membranes with notable proton conductivity (0.048 S cm –1 ) and tensile strength (12.21 MPa). Similarly, Yagmur et al reported successful cross-linking of PBI using different agents, with PBI/BADGE exhibiting superior performance in terms of current density (0.121 A cm –2 ) and maximum power density (123 mW cm –2 ).…”