Polybenzimidazole Composite Membrane Research Articles

Assessment of polybenzimidazole/MOF composite membranes for the improvement of high-temperature PEM fuel cell performance

This study aims to determine the most effective utilization of ZIF-8 type metal-organic framework (MOF) doped polybenzimidazole (PBI) composite membrane in high-temperature polymer electrolyte membrane fuel cells (HT-PEMFC) and investigate how ZIF-8 filler affects performance. ZIF-8 particles were prepared by solvothermal method and added to the PBI polymer using a weight percentage varying from 1 to 5 %. XRD, BET, and TEM examined the prepared ZIF-8. Composite membrane properties were investigated by XRD, SEM analysis, proton conductivity measurements, acid doping, and acid stripping tests. The HT-PEMFC performances of the membranes were carried out using Hydrogen and dry air at 150–180. The highest performance was acquired with the composite ZIF8/PBI-2 membrane as 0.432 W/cm2 at 170 °C. The obtained result is explained by easier proton transfer over ZIF-8's enlarged tunnel network. This study proposes a promising strategy to use ZIF-8 to prepare a PBI composite membrane with excellent proton conductivity, acid doping, and low acid leaching for HT-PEMFC application. The current study's findings can support future research on PBI/MOF-based composite membranes for HT-PEMFC applications.

Fabrication of high performance high-temperature proton exchange membranes through constructing stable cation-rich domain in polybenzimidazole membrane

Improving the power density (≤700 mW cm−2) and long-term durability of fuel cells are crucial for promoting the practical application of high-temperature proton exchange membrane fuel cells (HT-PEMFCs). In this study, a high-power density greater than 1000 mW cm−2 of fuel cell is obtained based on the designed polybenzimidazole (PBI) composite membranes containing cation-rich domains and stable two-phase interfaces. The newly designed membranes were fabricated by incorporating densely alkyl-bromide-functionalized polymer particles into the PBI membrane. The resulting composite membrane exhibited an improved mechanical strength of 12.6 MPa and high proton conductivity of 181.6 mS cm−1 at 160 °C. The power density of the corresponding composite membrane-based fuel cell reached 1090.5 mW cm−2 under a Pt loading of 0.6 mg cm−2 and H2/O2, without any humidification or backpressure at 160 °C, which is one of the most outstanding cell performances among all reported acid-doped high-temperature proton exchange membranes. Additionally, superior stability with a voltage decay rate of 0.0132 mV h−1 was observed in the long-term durability test. Thus, the proposed PBI composite membranes exhibit potential for use in HT-PEMFCs.

Enhancement of SO2 high temperature depolarized electrolysis by means of graphene oxide composite polybenzimidazole membranes

In the present work, Polybenzimidazole-composite membranes with graphene oxide as organic filler with different contents (0.5, 1.0, 2.0 and 3.0 wt%) were prepared and tested in a sulfur depolarized electrolyzer. The composite Graphene Oxide/Polybenzimidazole membranes show greater electrolyzer performance than a standard membrane. For the first time, actual hydrogen production is reported at high temperature in the range of 110 °C–140 °C for the sulfur dioxide depolarized electrolysis. In general, composite Graphene Oxide/Polybenzimidazole membranes showed superior performance, obtaining the highest hydrogen generation with the composite membrane with a content of 2 wt%. Furthermore, sulfur dioxide crossover is reported to decrease by increasing the amount of graphene oxide into the membrane, demonstrating the benefit of adding Graphene Oxide to a Polybenzimidazole matrix for the sulfur dioxide depolarized electrolysis.

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

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.

Composite membrane by incorporating sulfonated graphene oxide in polybenzimidazole for high temperature proton exchange membrane fuel cells

The objective of this work is to examine the polybenzimidazole (PBI)/sulfonated graphene oxide (sGO) membranes as alternative materials for high-temperature proton exchange membrane fuel cell (HT-PEMFC). PBI/sGO composite membranes were characterized by TGA, FTIR, SEM analysis, acid doping&acid leaching tests, mechanical analysis, and proton conductivity measurements. The proton conductivity of composite membranes was considerably enhanced by the existence of sGO filler. The enhancement of these properties is related to the increased content of –SO 3 H groups in the PBI/sGO composite membrane, increasing the channel availability required for the proton transport. The PBI/sGO membranes were tested in a single HT-PEMFC to evaluate high-temperature fuel cell performance. Amongst the PBI/sGO composite membranes, the membrane containing 5 wt. % GO (PBI/sGO-2) showed the highest HT-PEMFC performance. The maximum power density of 364 mW/cm 2 was yielded by PBI/sGO-2 membrane when operating the cell at 160 °C under non humidified conditions. In comparison, a maximum power density of 235 mW/cm 2 was determined by the PBI membrane under the same operating conditions. To investigate the HT-PEMFC stability, long-term stability tests were performed in comparison with the PBI membrane. After a long-term performance test for 200 h, the HT-PEMFC performance loss was obtained as 9% and 13% for PBI/sGO-2 and PBI membranes, respectively. The improved HT-PEMFC performance of PBI/sGO composite membranes suggests that PBI/sGO composites are feasible candidates for HT-PEMFC applications. • This study proposes PBI/sGO as an alternative membrane for HT-PEMFC application. • SGO was revealed as an effective filler for a PBI composite membrane for HT-PEMFC. • PBI/sGO membranes possess high proton conductivity. • PBI/sGO membrane with 5% GO content is a potential electrolyte for HT-PEMFC.

Sulfonated graphene oxide as an inorganic filler in promoting the properties of a polybenzimidazole membrane as a high temperature proton exchange membrane

A commercial perfluorinated sulfonic acid (PFSA) membrane, Nafion, shows outstanding conductivity under conditions of a fully humidified surrounding. Nevertheless, the use of Nafion membranes that operate only at low temperature (<100 °C) can lead to some disadvantages in PEMFC systems, such as a low impurity tolerance and slow kinetics. To overcome the above problems, this study introduces a highly durable composite membrane with an inorganic filler for a high-temperature proton exchange membrane fuel cell (HT-PEMFC) applications under anhydrous conditions. In this work, polybenzimidazole (PBI) is used as a polymer electrolyte membrane with the addition of a sulfonated graphene oxide (SGO) inorganic filler. The amount of SGO filler was varied (0.5–6 wt.%) to study its influence on proton conductivity at elevated temperature, mechanical stability as well as phosphoric acid doping level. In particular, PBI-SGO composite membranes exhibited higher the level of acid dopant and proton conductivities than those of the pure PBI membranes. The PBI-SGO 2 wt.% composite membrane displayed the highest proton conductivity, with a value of 9.142 mS cm−1 at 25 °C, and it increased to 29.30 mS cm−1 at 150 °C. The PBI-SGO 2 wt.% also displayed the maximum values in the acid doping level (11.63 mol of PA/PBI repeat unit) and mechanical stability (48.86 MPa) analyses. In the HT-PEMFC test, compared with a pristine PBI membrane, the maximum power density was increased by 40% with the use of a PBI composite membrane with 2 wt.% SGO. These results show that the PBI-SGO membrane has a great potential to be applied as an alternative membrane in HT-PEMFC applications, offering the possibility of improving impurity tolerance and kinetic reactions.

Polybenzimidazole composite membranes containing imidazole functionalized graphene oxide showing high proton conductivity and improved physicochemical properties

Polymer composite membranes are fabricated using poly[2,2'-(m-phenylene)-5,5′-bibenzimidazole] (PBI) as a polymer matrix and imidazole functionalized graphene oxide (ImGO) as a filler material for high temperature proton exchange membrane fuel cell applications. ImGO is prepared by the reaction of o-phenylenediamine with graphene oxide (GO). The compatibility of ImGO with PBI matrix is found to be better than that of GO, and as a result PBI composite membrane having ImGO exhibits improved physicochemical properties and larger proton conductivity compared with pure PBI and PBI composite membrane having GO. For example, PBI composite membrane having 0.5 wt% of ImGO shows enhanced tensile strength (219.2 MPa) with minimal decrease of elongation at break value (28.8%) compared with PBI composite membrane having 0.5 wt% of GO (215.5 MPa, 15.4%) and pure PBI membrane without any filler (181.0 MPa, 34.8%). The proton conductivity of this membrane, at 150 °C under anhydrous condition, is 77.52 mS cm−1.

Ionic Liquid Composite Polybenzimidazol Membranes for High Temperature PEMFC Applications.

A series of proton exchange membranes based on polybenzimidazole (PBI) were prepared using the low cost ionic liquids (ILs) derived from 1-butyl-3-methylimidazolium (BMIM) bearing different anions as conductive fillers in the polymeric matrix with the aim of enhancing the proton conductivity of PBI membranes. The composite membranes prepared by casting method (containing 5 wt. % of IL) exhibited good thermal, dimensional, mechanical, and oxidative stability for fuel cell applications. The effects of anion, temperature on the proton conductivity of phosphoric acid-doped membranes were systematically investigated by electrochemical impedance spectroscopy. The PBI composite membranes containing 1-butyl-3-methylimidazolium-derived ionic liquids exhibited high proton conductivity of 0.098 S·cm−1 at 120 °C when tetrafluoroborate anion was present in the polymeric matrix. This conductivity enhancement might be attributed to the formed hydrogen-bond networks between the IL molecules and the phosphoric acid molecules distributed along the polymeric matrix.

Preparation of Novel Polyaniline and Phosphoric Acid Doped Sulfonated Polybenzimidazole Composite Membranes for Fuel Cells

Polyaniline (PANI) and phosphoric acid (PA) doped sulfonated polybenzimidazole (SPBI) composite membrane was prepared for application in high-temperature proton exchange membrane (PEMFC) without the need of humidification. The synthesis and characterization of targed composite membrane were introduced in this paper.

ZIF‐11/Polybenzimidazole composite membrane with improved hydrogen separation performance

ABSTRACTZeolitic imidazolate framework (ZIF)‐11 crystals were prepared by the toluene‐assisted method, and they were incorporated into polysulfone, polyethersulfone, and polybenzimidazole (PBI) matrix to investigate the compatibility. ZIF‐11 had a good connection with PBI matrix as they had the same benzimidazole groups. The evaporation temperature of the membrane formation was studied with two different solvents: N‐methyl‐2‐pyrrolidone (NMP) and N,N‐dimethylacetamide (DMAc). Then, the ZIF‐11/PBI composite membranes prepared using NMP or DMAc as the solvent were characterized and tested by gas separation. Improved H2 and CO2 permeabilities with a H2/CO2 ideal selectivity of 5.6 were obtained on the 16.1 wt % ZIF‐11/PBI composite membrane prepared with DMAc as the solvent. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41056.

Mechanical Stability of H3PO4-Doped PBI/Hydrophilic-Pretreated PTFE Membranes for High Temperature PEMFCs

A novel polybenzimidazole (PBI)/poly(tetrafluoroethylene) (PTFE) composite membrane doped with phosphoric acid was fabricated for high temperature operation in a polymer electrolyte membrane (PEM) fuel cell. A hydrophilic surface pretreatment was applied to the porous PTFE matrix film to improve its interfacial adhesion to the PBI polymer, thereby avoiding the introduction of Nafion ionomer which is traditionally used as a coupling agent. The pretreated PTFE film was embedded within the composite membrane during solution-casting using 5wt% PBI/DMAc solution. The mechanical stability and durability of three types of MEAs assembled with PBI only, PBI with pretreated PTFE, and PBI-Nafion with untreated PTFE membranes were evaluated under an accelerated degradation testing protocol employing extreme temperature cycling. Degradation was characterized by recording polarization curves, hydrogen crossover, and proton resistance. Cross-sections of the membranes were examined before and after thermal cycling by scanning electron microscope. Energy-dispersive X-ray spectroscopy verified that the PBI is dispersed homogeneously in the porous PTFE matrix. Results show that the PBI composite membrane with pretreated PTFE has a lower degradation rate than the Nafion/PBI membrane with untreated PTFE. Thus, the hydrophilic pretreatment employed here greatly improved the mechanical stability of the composite membrane, which resulted in improved durability under an extreme thermal cycling regime.

Sulfonated MWNT and imidazole functionalized MWNT/polybenzimidazole composite membranes for high-temperature proton exchange membrane fuel cells

Composite membranes used for proton exchange membrane fuel cells comprising of polybenzimidazole (PBI) and carbon nanotubes with certain functional groups were studied, because they could enhance both the mechanical property and fuel cell performance at the same time. In this study, sodium poly(4-styrene sulfonate) functionalized multiwalled carbon nanotubes (MWNT-poly(NaSS))/PBI and imidazole functionalized multiwalled carbon nanotubes (MWNT-imidazole)/PBI composite membranes were prepared. The functionalization of carbon nanotubes involving non-covalent modification and covalent modification were confirmed by FITR, XPS, Raman spectroscopy, and TGA. Compared to unmodified MWNTs and MWNT-poly(NaSS), MWNT-imidazole provided more significant mechanical reinforcement due to its better compatibility with PBI. For MWNT-poly(NaSS)/PBI and MWNT-imidazole/PBI composite membranes at their saturated doping levels, the proton conductivities were up to 5.1 × 10−2 and 4.3 × 10−2 S/cm at 160 °C under anhydrous condition respectively, which were slightly higher than pristine PBI (2.8 × 10−2 S/cm). Also, MWNT-poly(NaSS)/PBI and MWNT-imidazole/PBI composite membranes showed relatively improved fuel cell performance at 170 °C compared to pristine PBI.

Polybenzimidazole composite membranes for high temperature synthesis gas separations

High temperature gas separation techniques are of great interest for reduction in green-house gas emissions from hydrocarbon fuels such as natural gas, coal or biomass used in power and chemical industry. In this work, a robust industrially viable polybenzimidazole (PBI)/stainless steel composite membrane is developed and evaluated for syngas separations at elevated temperatures for H2 production. A single tube laboratory scale PBI membrane module is tested for H2/CO2 perm-selectivity in pure and simulated dry syngas environments at industrially relevant operating conditions. Additionally, the effects of pressure and temperature on membrane performance are evaluated. The PBI composite membrane demonstrated exceptional long term thermo-chemical stability in the syngas environment even in the presence of H2S and excellent separation performance for H2 over the other syngas components. The H2 permeance and H2/CO2 selectivity for the PBI composite membrane in simulated dry syngas was recorded at 7 GPU (approximately, 88 barrer) and 47, respectively. In comparison to the other H2-selective polymeric membranes, the PBI composite membrane's performance exceeded the 2008 Robeson upper bound for the H2/CO2 permeability versus selectivity.

Pyridine‐based PBI Composite Membranes for PEMFCs

AbstractPolybenzimidazole (PBI) activated with H3PO4 is one of the membranes of choice to replace Nafion® in PEMFCs in order to allow their use above 100 °C. The limits of PBI in terms of acid leaching and low conductivity below 160 °C can be overcome by a proper monomer tailoring, and by the addition of new fillers. Here, we report on new pyridine‐based PBI membranes with: (i) imidazole‐silica (SiO2‐Im) and (ii) mesostructured silica (SBA‐15) fillers. Both the thermal stability and the permanent conductivity are improved by adding 5 wt.‐% of filler, but SiO2‐Im gives the best results. Permanent conductivity values higher than 10–3 S cm–1 are obtained at 120 °C and 50% R.H. Vibrational spectroscopies (FT‐IR and Raman) are used to investigate the relationships among the polymer, the filler and the activating H3PO4 acid.

Proton conductivity of zirconium tricarboxybutylphosphonate/PBI nanocomposite membrane

The preparation process and proton transport properties of zirconium tricarboxybutylphosphonate Zr(O3PC(CH2)3(COOH)3)2 (Zr(PBTC))/polybenzimidazole (PBI) composite membranes have been investigated with a view to developing a novel electrolyte for direct methanol fuel cells. A compacted Zr(PBTC) powder sample and a Zr(PBTC)/PBI composite membrane with 50 wt.% Zr(PBTC) content show conductivities of 6.74 × 10–2 S cm–1 and 3.82 × 10–3 S cm–1 at 200 °C under a fully humid condition, respectively. Post-sulfonation thermal treatment, which has a great effect on the ligand structure of PBI, gives a marked increase in the conductivity of the membrane by a factor of 2 in the same condition. This effect is mainly attributed to the proton transport via sulfonic acid groups bonded to the PBI unit.

Proton conductivity of phosphoric acid doped polybenzimidazole and its composites with inorganic proton conductors

Phosphoric acid doped polybenzimidazole (PBI) and PBI composite membranes have been prepared in the present work. The PBI composites contain inorganic proton conductors including zirconium phosphate (ZrP), (Zr(HPO 4) 2· nH 2O), phosphotungstic acid (PWA), (H 3PW 12O 40· nH 2O) and silicotungstic acid (SiWA), (H 4SiW 12O 40· nH 2O). The conductivity of phosphoric acid doped PBI and PBI composite membranes was found to be dependent on the acid doping level, relative humidity (RH) and temperature. A conductivity of 6.8×10 −2 S cm −1 was observed for PBI membranes with a H 3PO 4 doping level of 5.6 (mole number of H 3PO 4 per repeat unit of PBI) at 200 °C and 5% RH. A higher conductivity of 9.6×10 −2 S cm −1 was obtained by composite of 15 wt.% of ZrP in a PBI membrane under the same conditions. Homogeneous membranes with good mechanical strength were prepared by introducing PWA (20–30 wt.%) and SiWA (20–30 wt.%) into PBI, and their conductivity were found to be higher than or comparable with that of the PBI membrane at temperatures up to 110 °C.