Nitrogen Dense Distributions of Imidazole Grafted Dipyridyl Polybenzimidazole for a High Temperature Proton Exchange Membrane

Abstract

The introduction of basic groups in the polybenzimidazole (PBI) main chain or side chain with low phosphoric acid doping is an effective way to avoid the trade-off between proton conductivity and mechanical strength for high temperature proton exchange membrane (HT-PEM). In this study, the ethyl imidazole is grafted on the side chain of the PBI containing bipyridine in the main chain and blended with poly(2,2′-[p-oxydiphenylene]-5,5′-benzimidazole) (OPBI) to obtain a series of PBI composite membranes for HT-PEMs. The effects of the introduction of bipyridine in the main chain and the ethyl imidazole in the side chain on proton transport are investigated. The result suggests that the introduction of the imidazole and bipyridine group can effectively improve the comprehensive properties as HT-PEM. The highest of proton conductivity of the obtained membranes under saturated phosphoric acid (PA) doping can be up to 0.105 S cm−1 at 160 °C and the maximum output power density is 836 mW cm−2 at 160 °C, which is 2.3 times that of the OPBI membrane. Importantly, even at low acid doping content (~178%), the tensile strength of the membrane is 22.2 MPa, which is nearly 2 times that of the OPBI membrane, the proton conductivity of the membrane achieves 0.054 S cm−1 at 160 °C, which is 2.3 times that of the OPBI membrane, and the maximum output power density of a single cell is 540 mW cm−2 at 160 °C, which is 1.5 times that of the OPBI membrane. The results suggest that the introduction of a large number of nitrogen-containing sites in the main chain and side chain is an efficient way to improve the proton conductivity, even at a low PA doping level.

Perspectives on Membrane Development for High Temperature Proton Exchange Membrane Fuel Cells

“…Moreover, PBI's side chain can also be grafted with ethyl imidazole. 90 In comparison with the OPBI membrane, the copolymer membrane containing dipyridyl PBI increased proton conduction and peak power density by 3.8 and 1.7 times, respectively, at a high ADL of 260%. Grafting ethyl imidazole onto the side chain increased the PA absorption and produced a power density of 540 mW•cm −2 even at low ADL (179%).…”

“…It was verified by both groups that adding benzimidazole may raise the proton conductivity by increasing the PA doping level. Moreover, PBI’s side chain can also be grafted with ethyl imidazole . In comparison with the OPBI membrane, the copolymer membrane containing dipyridyl PBI increased proton conduction and peak power density by 3.8 and 1.7 times, respectively, at a high ADL of 260%.…”

Progress in High Temperature Proton Exchange Membranes for Fuel Cell

“…1.4 引入碱性基团 在PBI主链中引入碱性基团 [31] 可以增加对磷酸分子亲附力，有效地提高磷酸掺 杂率，表现出较高的质子传导率。 Jana等 [32] 使用2，6-双(3′，4′-二氨基苯基) 并咪唑(PB-PBI [33] ，如图8所示)。将扭曲、非共 面二氮芴(Cardo型)结构 [34][35][36][37] 引入PBI主链中， 可以打乱分子链的有序堆叠提高聚合物的溶解加 工性。在280℃、315℃和350℃条件下制备了一系 列热固化的PBPBI膜。芬顿试验结果表明，交联膜 表 2 TADPS-IPA、TADPS-TPA、TADPS-OBA和m-PBI在各溶剂 中的溶解性 [27] Table 2 Solubility of TADPS-IPA,TADPS-TPA,TADPS-OBA and m-PBI in various solvents [27] 聚合物 NMP DMAc DMSO THF…”

Grafting of Amine End-Functionalized Side-Chain Polybenzimidazole Acid–Base Membrane with Enhanced Phosphoric Acid Retention Ability for High-Temperature Proton Exchange Membrane Fuel Cells

“…The PA/PBI membrane is generally prepared through immersing a PBI membrane obtained by the solution casting method into PA for a certain time to allow PA molecules to enter the membrane. In order to obtain sufficient proton conductivity, great efforts have been made to increase the PA uptake of the PBI membrane [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ].…”