Polybenzimidazole Films Research Articles

(Invited) NMR Investigation of Proton Transport in Concentrated Aqueous and Polymer Electrolytes Based on Polyphosphoric Acid

Concentrated aqueous electrolytes have received much attention in recent years due to their high ionic conductivity and electrochemical window that usually exceeds that of the water electrolysis limitation. In collaboration with Ziyue Li and Fei Wang (Fudan University) we have investigated water/polyphosphoric acid solutions ranging in concentration from 1.25 to 16.6 molar being considered for proton-based batteries. Self-diffusion coefficients measured by pulsed field gradient NMR as well as spin-lattice time relaxation measurements were determined for 31P and 1H. The results shed light on the observed maximum in conductivity at the 5.9 molar concentration.For polymer electrolyte membrane fuel cells (PEMFC), polybenzimidazole (PBI) membranes with high phosphoric acid content have been developed previously by collaborator Brian Benicewicz (University of South Carolina) using the so-called PPA process. Recently, a carefully controlled drying method has been discovered by Benicewicz and co-worker Laura Murdock in which a PBI membrane prepared by the PPA process is transformed into a dense PBI film. Though originally developed for flow battery applications, it was found that this dense film could be re-acidified to yield a mechanically robust PEM. Furthermore this method provides a synthetic route to PBI films without the use of any organic solvents. The re-doped PBI films display high ionic conductivity at elevated temperatures, similar to the starting PBI gel membranes prepared by the PPA process, while containing nearly a factor of two less acid than the latter and also exhibiting enhanced mechanical properties. NMR spectroscopy was used to characterize the structure and dynamics of the modified and the original PBI/PPA membranes. In addition to pulsed field gradient diffusion studies, we have performed solid state one-dimensional 31P, 13C and two-dimensional 31P{1H} and 13C{1H} HETCOR NMR measurements, which yield additional information on structural differences between the membranes and how these differences may affect transport properties.

Single-Layer-Graphene and Electrochemical Exfoliated Graphene Oxide for HT-PEMFC

High-temperature proton exchange membrane fuel cell (HT-PEMFC) is promising with its low demand for hydrogen purity, simple water management, and high waste heat utilization [1][2]. Although polybenzimidazole (PBI), as a typical high-temperature fuel cell membrane, has been developed for a long period, it still has defects such as phosphoric acid leaching and insufficient mechanical properties under high acid doping level [3][4]. With its unique 2D hexagonal grid structure and its electron cloud arrangement, single-layer graphene (SLG) can block the passage of any atoms [5]. However, hydrogen protons can easily penetrate SLG through a unique intermediate state mechanism to make it have excellent proton conductivity [6]. SLG's high proton conductivity combined with its excellent mechanical properties and thermal conductivity make it an ideal material for blocking phosphoric acid leaching. The SLG prepared by the chemical vapor deposition (CVD) method was transferred to the surface of catalyst layer of electrodes by the wet chemical transfer method. Due to the rupture and incompleteness of the SLG during the transfer process, the coverage rate of the SLG on the electrode surface is about 55%. This incomplete coverage facilitates small quantities of phosphoric acid leaching from PBI membrane to electrodes, which increases the three-phase boundary area and improves the performance of the HT-PEMFC. After 70 hours of accelerated stress testing (AST), the peak power density of membrane-electrode-assembly (MEA) with SLG on both sides of the cathode and anode can reach 480 mW cm-2, while the peak power density of MEA based on pure PBI membrane is only 249 mW cm-2. The quantification of phosphoric acid in the electrode by Lab based X-ray micro-computed tomography and the Raman spectroscopic mapping of the MEA cross-section shows that SLG can mitigate the leaching of phosphoric acid in the PBI film and improve the durability of HT-PEMFC. Graphene oxide (GO) is a low-cost application of graphene. Its doping in the PBI membrane can also reduce the leaching of phosphoric acid through enhancing the interaction between phosphoric acid and the PBI membrane [7]. A reactor based on 3D printing was designed so that natural graphite flakes can be used for electrochemical exfoliation to achieve rapid, safe, environmentally friendly, and mass production of GO. The electrochemically exfoliated (E)GO is doped in the PBI membrane. The 0.5%, 1% and 2% EGO loadings in the PBI membrane increased the peak power density by 13.8%, 24.4% and 29.2%, respectively.[1] Y.-L. Ma, J.S. Wainright, M.H. Litt, R.F. Savinell, Conductivity of PBI Membranes for High-Temperature Polymer Electrolyte Fuel Cells, Journal of The Electrochemical Society. 151 (2004) A8. https://doi.org/10.1149/1.1630037/XML.[2] H. Su, S. Pasupathi, B. Bladergroen, V. Linkov, B.G. Pollet, Optimization of gas diffusion electrode for polybenzimidazole-based high temperature proton exchange membrane fuel cell: Evaluation of polymer binders in catalyst layer, International Journal of Hydrogen Energy. 38 (2013) 11370–11378. https://doi.org/10.1016/J.IJHYDENE.2013.06.107.[3] S. Galbiati, A. Baricci, A. Casalegno, R. Marchesi, Degradation in phosphoric acid doped polymer fuel cells : A 6000 h parametric investigation, International Journal of Hydrogen Energy. 38 (2013) 6469–6480. https://doi.org/10.1016/j.ijhydene.2013.03.012.[4] S.H. Eberhardt, F. Marone, M. Stampanoni, F.N. Büchi, T.J. Schmidt, Quantifying phosphoric acid in high-temperature polymer electrolyte fuel cell components by X-ray tomographic microscopy, Journal of Synchrotron Radiation. 21 (2014) 1319–1326. https://doi.org/10.1107/S1600577514016348.[5] S. Hu, M. Lozada-Hidalgo, F.C. Wang, A. Mishchenko, F. Schedin, R.R. Nair, E.W. Hill, D.W. Boukhvalov, M.I. Katsnelson, R.A.W. Dryfe, I. V. Grigorieva, H.A. Wu, A.K. Geim, Proton transport through one-atom-thick crystals, Nature. 516 (2014) 227–230. https://doi.org/10.1038/nature14015.[6] S.M. Holmes, P. Balakrishnan, V.S. Kalangi, X. Zhang, M. Lozada-Hidalgo, P.M. Ajayan, R.R. Nair, 2D Crystals Significantly Enhance the Performance of a Working Fuel Cell, Advanced Energy Materials. 7 (2017) 1–7. https://doi.org/10.1002/aenm.201601216.[7] J. Li, X. Zeng, T. Ren, E. van der Heide, The Preparation of Graphene Oxide and Its Derivatives and Their Application in Bio-Tribological Systems, Lubricants 2014, Vol. 2, Pages 137-161. 2 (2014) 137–161. https://doi.org/10.3390/LUBRICANTS2030137.

Reinforcement of ultrahigh thermoresistant polybenzimidazole films by hard craters

Ultrahigh thermoresistant polybenzimidazole films with uniform pores and hard craters on the surface were prepared by a silica template method. The pore and crater formation enhanced elongation and Young's modulus.

NMR Investigation of Transport in Polybenzimidazole/Polyphosphoric Acid Membranes Prepared Via Novel Synthesis Route

Previous work by the some of us has demonstrated enhanced electrochemical performance of polybenzimidazole (PBI) membranes with high phosphoric acid content prepared by the so-called PPA process.1 Methods of PBI synthesis that involve casting from an organic solvent cannot incorporate the more rigid PBIs characteristic of the PPA process due to their limited solubility. Recently, a carefully controlled drying method has been discovered in which a gel PBI membrane, made in the PPA process, is transformed into a dense PBI film. This method provides a synthetic route to PBI films without the use of any organic solvents. The dense PBI films with repeat unit para-PBI (Fig.1), were originally developed for flow battery applications. However they also can be re-doped in phosphoric acid to be used as a membrane in high-temperature fuel cells.The re-doped PBI films have displayed unprecedented ionic conductivity at elevated temperatures, similar to the starting PBI gel membranes prepared by the PPA process1, while also exhibiting enhanced mechanical properties. Temperature-dependent conductivity data for two of these films are displayed below. Sample A is the dried, densified, and re-acidified version of sample B, with a much lower acid content, ~18 mol PA/PBI repeat unit compared to 30 mol PA/PBI RU, respectively, but exhibits comparable conductivity (Fig. 2). Thus, in high-temperature fuel cell operation the electrochemical performance is similar, but performance degradation due to mechanical creep is reduced, leading to greater durability of the Version A PBI.In attempting to understand the enhanced proton conductivity of the modified PBI membrane despite its lower acid content, we performed both 1H and 31P nuclear magnetic resonance (NMR) measurements. Proton self-diffusion coefficients for four membranes two (A,C) prepared by the modified process and two (B,D) by the original PPA process, were measured by pulsed gradient NMR and plotted in Fig. 3.The results show significantly enhanced proton diffusivity, both in magnitude and in lower activation energy for sample A, which is consistent with its high conductivity despite lower acid content compared to the original PPA-processed membranes (B, D). We have also performed solid state 1D 31P and 2D 31P{1H} HETCOR NMR measurements, which yield additional information on structural differences between the membranes and how these differences may affect transport properties. Multinuclear NMR Study of the Effect of Acid Concentration on Ion Transport in Phosphoric Acid Doped Polybenzimidazole Membranes, N. Suarez, N.K.A.C. Kodiweera, P. Stallworth, S.G. Greenbaun, S. Yu, and B. Benicewicz, Journal of Physical Chemistry B, 116, 12545-51(2012). Figure 1

Green Preparation of Thin Films of Polybenzimidazole on Flat and Hollow Fiber Supports: Application to Hydrogen Separation.

This work shows the preparation of thin films, with thickness from 70 nm to 1 μm, of meta-polybenzimidazole (m-PBI) on polyimide P84 supports. Ethanolic solutions of m-PBI were used to coat flat and hollow fiber supports of asymmetric P84 with m-PBI in a process where the coating and drying was performed at room temperature. A solution of NaOH in EtOH allowed the dissolution of the m-PBI powder, providing the perfect coating solution to build thin films of m-PBI without damaging the polymeric support. It also meant a green alternative, avoiding the use of toxic solvents, such as dimethylacetamide. The resulting membranes have been tested for the separation of H2 mixtures at high temperature at different setups to allow checking their reproducibility. With 100 nm thickness the membranes showed their best gas separation performance. For flat membranes at 180 °C and 3 bar feed pressure a H2 permeance of 48.5 GPU was obtained, with respective H2 /CO2 and H2 /N2 selectivities of 33.3 and 55.8. Besides, the hollow fibers under a feed pressure of 6 bar and tested at the same temperature showed near 90 GPU of H2 with a H2 /CO2 selectivity of 13.5 in the one-fiber module and over 39 GPU of H2 with a H2 /CO2 selectivity of 20.2 in the five-fiber module. Finally, the stability of the membranes was proved for 22 days at 180 °C.

Highly Porous Fluorescent Materials Based on Polymer Matrices Impregnated with Eu(dbm)3 Molecules in a Supercritical Carbon Dioxide Medium

The possibility of creating luminescent films based on highly porous polymer materials doped with the europium complex Eu(dbm)3 · H2O in a supercritical carbon dioxide medium using ethanol as a co-solvent is demonstrated. The initial polymer samples are polytetrafluoroethylene films obtained using thermal spraying or electrospinning techniques and polybenzimidazole films with foam-like structures obtained using laser irradiation. Deposition of the Eu complex in the pores of such materials (up to a few micrometers in size) leads to the appearance of bright characteristic photoluminescence (PL) in the red region, the intensity of which depends on the impregnation method and subsequent processing of the samples. An analysis of the intensity ratio between the electric dipole and magnetic dipole components of the PL spectra allow us to draw conclusions about the changes in the nearest environment of Eu3+ ions in each of the studied host materials.

UV Photo-Oxidation of Polybenzimidazole (PBI)

Since polybenzimidazole (PBI) is often used in the aerospace industry, high-temperature fuel cells, and in redox flow batteries, this research investigated the surface modification of PBI film with 253.7 and 184.9 nm UV photo-oxidation. As observed by X-ray photoelectron spectroscopy (XPS), the oxygen concentration on the surface increased up to a saturation level of 20.2 ± 0.7 at %. With increasing treatment time, there were significant decreases in the concentrations of C-C sp2 and C=N groups and increases in the concentrations of C=O, O-C=O, O-(C=O)-O, C-N, and N-C=O containing moieties due to 253.7 nm photo-oxidation of the aromatic groups of PBI and reaction with ozone produced by 184. 9 nm photo-dissociation of oxygen. Because no significant changes in surface topography were detected by Atomic Force Microscopy (AFM) and SEM measurements, the observed decrease in the water contact angle down to ca. 44°, i.e., increase in hydrophilic, was due to the chemical changes on the surface.

Formation of luminescent states in polybenzimidazole‐based films

AbstractHere we present the results of experimental studies and theoretical computations of the spectroscopic parameters of polybenzimidazole (PBI) films formed by casting from a formic acid solution. The kinetics of the polymer luminescence is described, depending on the amount of the residual solvent. We demonstrate the changes in the intensity of the film luminescence with the formic acid release from the film, which is confirmed by the IR data. Based on the quantum chemistry computations, a mechanism is suggested for the formation of absorption and luminescence bands characteristic of the PBI matrix.

A comparative experimental study of the hygroscopic and mechanical behaviors of electrospun nanofiber membranes and solution‐cast films of polybenzimidazole

AbstractThis article reports a comparative experimental study of the hygroscopic and mechanical behaviors of electrospun polybenzimidazole (PBI) nanofiber membranes and solution‐cast PBI films. As‐electrospun nonwoven PBI nanofiber mats (with the nanofiber diameter of ~250 nm) were heat‐pressed under controlled temperature, pressure and duration for the study; lab‐made solution‐cast PBI films and commercially available PBI films (the PBI Performance Product Inc., Charlotte, NC) were used as the control samples. Thermogravimetric and microtensile tests were utilized to characterize the hygroscopic (moisture absorption) and mechanical properties of the PBI nanofiber membranes at varying heat‐pressing conditions, which were further compared to those of solution‐cast PBI films. Experimental results indicated that the PBI nanofiber membranes carried slightly higher thermal stability and less hygroscopic properties than those of solution‐cast PBI films. In addition, heat‐pressing conditions significantly influenced the mechanical properties of the resulting PBI nanofiber membranes. The stiffness and tensile strength increase with increasing either the heat‐pressing pressure or duration, and relevant mechanisms were explored. The present study provides a rational understanding of the hygroscopic and mechanical behaviors of electrospun PBI nanofiber membranes and solution‐cast PBI films that are beneficial to their reliable cutting‐edge applications in high‐temperature filtration, polymer electrolyte membranes (PEMs), etc.

Composite Membranes Containing a Porous Separator and a Polybenzimidazole Thin Film for Vanadium Redox Flow Batteries

Redox flow batteries (RFBs) are energy storage devices designed for grid-scale application. For next generation RFBs it is desirable to develop low cost materials with low ohmic resistance and high transport selectivity. We present a composite membrane for the vanadium redox flow battery (VRFB) consisting of a composite of a porous polypropylene separator laminated with a thin film of polybenzimidazole (PBI). PBI layers are prepared by solution casting to obtain thicknesses in the range of 0.2 to 10 μm. The ohmic resistance of vanadium electrolyte imbibed PBI is ∼50 mOhm·cm2 per micrometer of film thickness at room temperature. In cell tests, composite membranes show higher coulombic efficiency compared to Nafion® 212. Composite membranes with a PBI layer thickness of 1 μm and below outperform Nafion® 212 in terms of energy efficiency and discharge capacity up to a current density of 250 mA cm−2. With thicker PBI films the ohmic cell resistance is excessively high. Over 100 charge-discharge cycles a higher rate of capacity fading is observed for a composite membrane with 0.7 μm PBI compared to Nafion® 212, which is a result of a more pronounced net electrolyte flux from the negative to the positive electrolyte.

Polybenzimidazole nanofibers for neural stem cell culture

Neurodegenerative diseases compromise the quality of life of an increasing number of people in the world's aging population. While diagnosis is possible, no effective treatments are available. Strong efforts are needed to develop new therapeutic approaches, namely, in the areas of tissue engineering and deep brain stimulation. Conductive polymers are the ideal material for these applications owing to the positive effect of conducting electricity on the neural cell's differentiation profile. This novel study assessed the biocompatibility of polybenzimidazole (PBI) as electrospun fibers and after being doped with different acids. First, doped films of PBI were used to characterize the materials' contact angle and electroconductivity. After this, fibers were electrospun and characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. Neural stem cell (NSC) proliferation was assessed, and their growth rate and morphology on different samples were determined. Differentiation of NSCs on PBI-β-camphorsulfonic acid (CSA) fibers was also investigated, and gene expression (SOX2, NES, GFAP, and Tuj1) was assessed through immunochemistry and quantitative real-time polymerase chain reaction. All the samples tested were able to support NSC proliferation without significant changes on the cell's typical morphology. Successful differentiation of NSCs toward neural cells on PBI-CSA fibers was also achieved. This promising PBI fibrous scaffold material is envisioned to be used in neural cell engineering applications, including scaffolds and in vitro models for drug screening and electrodes.

Polybenzimidazole thermal management composites containing functionalized boron nitride nanosheets and 2D transition metal carbide MXenes

Recently, polymer-based thermal management materials have been receiving more and more attention. Always, introducing the thermal conductive nanofillers to prepare polymer composites is one of the best ways to improve the thermal conductivity (TC) of the polymer. However, the simple and effective way to improve thermal conductivity by increasing fillers loading amount often brings the decrease of mechanical property resulted by agglomeration. Herein, we combined 2D transition metal carbides (Ti3C2Tx), and functionalized boron nitride nanosheets (f-BNNS) together for simultaneously enhancing the TC and mechanical property of polybenzimidazole (PBI)-based composites. As the loading amounts of f-BNNS-Ti3C2Tx reached 25 wt% (f-BNNS: 12.5 wt%, Ti3C2Tx: 12.5 wt%), the in-plane and through-plane TCs of the f-BNNS-Ti3C2Tx/PBI composite film reach ~5.06 and ~3.44 W m−1 K−1 which are ~12.05 and ~8.19 times higher than those of neat PBI film. More notably, the synergistic effect of interspace-filling and bridging between f-BNNS and Ti3C2Tx also prevents the agglomeration and facilitates the improvement of mechanical property, even at a high loading amount of 25 wt%, the yield and ultimate tensile strengths of f-BNNS-Ti3C2Tx/PBI composite film are ~175.5 and ~189.6 MPa with increases of ~61.1% and ~39.8% compared to those of neat PBI.

H2/CO2 separation enhancement via chemical modification of polybenzimidazole nanostructure

Polybenzimidazole (PBI) thin films were chemically crosslinked using 1,3,5-Tris(bromomethyl)benzene (TBB) to manipulate the microstructure of polymer chains and to achieve a high sieving ability for H2/CO2 separation. By changing the TBB concentration and TBB/PBI molar ratio in the crosslinking solutions, PBI films were modified with different degrees of crosslinking. The increment of crosslinking density in the membranes leads to a decrease in fractional free volume (FFV), indicating the tightening effect of the TBB crosslinking reaction on PBI films. The H2/CO2 mixed gas separation was conducted at 150 °C. The membrane with the highest crosslinking density and the lowest FFV possesses the best performance for H2/CO2 separation with a H2 permeability of 9.6 Barrer and a remarkable H2/CO2 selectivity of 24. It surpasses the Robeson's upper bound and some of other membranes, indicating its promise for hydrogen purification and CO2 capture at elevated temperatures.

An electrode-supported fabrication of thin polybenzimidazole membrane-based polymer electrolyte membrane fuel cell

H3PO4-doped polybenzimidazole (PBI) membranes have been employed for high temperature polymer electrolyte membrane fuel cell (HT-PEMFC). Although a thinner PBI membrane is beneficial in enhancing power performance, the use of thin PBI membrane has been hindered by its poor mechanical property and consequent difficulty in membrane handling during membrane electrode assembly (MEA) fabrication. Here, novel fabrication route to realize a thin PBI membrane (∼35 μm)-based HT-MEA is presented. The key feature of the process is to fabricate thin blend membrane of PBI and poly(ethylene glycol) (PEG) and laminate the blend membrane to anode gas diffusion electrode (GDE) followed by H3PO4 doping. The introduction of PEG to PBI film enables the tight bonding of the membrane to the GDE at a mild lamination temperature and mitigates the membrane expansion with the doping, preserving the tight interfacial bonding. Due to the lowered membrane thickness, the corresponding MEA exhibits a high power density of 264 mW cm-2 at 0.6 V. Therefore, the new fabrication strategy based on the blend of PBI/PEG is highly effective in improving both process and power performance of HT-MEA.

Reaction of ozone with polybenzimidazole (PBI)

ABSTRACTOzone reacted with the polybenzimidazole (PBI) film surface and X-ray photoelectron spectroscopy (XPS) detected a rapid increase in O atom concentration up to a saturation level of 27 ± 1 atomic %. Atomic force microscopy measurements showed little change in surface roughness. The water contact angle of the treated film decreased by ca. 60% compared to untreated PBI film indicating an increase in hydrophilicity and hydrogen bonding due the formation of the polar oxygenated functional groups. With treatment, the curve fitting of the XPS chemical states showed a decrease in the C–C sp2, C–C sp3, and C=N functional groups, and an increase in C–N, C=O, O–C=O, O–(C=O)–O, and N–C=O moieties which were explained using mechanisms associated with the dissociation of the primary ozonide formed from the addition of ozone to the C=C and C=N bonds and reaction with the amine groups in PBI. Washing the treated surface with water partially washed away the O concentration which indicated the formation of a weak boundary layer due to the breakage of bonds in the decomposition of the primary ozonide.

Polybenzimidazole (PBI) film coating for improved hypervelocity impact energy absorption for space applications

This paper deals with how the use of Polybenzimidazole (PBI) as a film coating over conventional composite designs could help improve the hypervelocity impact ballistic performance of the system. PBI coated composite samples were studied for resistance to Low Earth Orbit environment conditions like high vacuum, thermal cycling, Atomic Oxygen and Ultraviolet Radiation in a simulation facility. It was observed that the PBI coated composites reduced mass loss and surface erosion compared to the non-coated samples after LEO exposure. Hypervelocity impact experiments were conducted on the PBI coated composites for impact velocities between 2.5 to 3 km/s. The experiments showed that the PBI film coating significantly increased the energy absorption of the composite system. The effect of thickness increase as a result of the film application on energy absorption was also found to be negligible confirming the effectiveness of PBI coating as a hypervelocity shield.

A very low concentration of polybenzimidazole film interleaved bismaleimide/diallyl bisphenol a system with outstanding improvement in impact strength and excellent allround properties

A very low concentration of thermoplastic polybenzimidazole (PBI) film interleaved bismaleimide/diallyl bisphenol A (BMI/DBA) system with sandwich structure was designed for the outstanding impact resistance. The effects of PBI film layers (0∼5) on the mechanical, thermal, dielectric properties and flame retardancy of BMI/DBA were investigated. BMI/DBA interleaved with 5‐layer PBI film demonstrates a 274% increase in impact strength relative to BMI/DBA, and exhibits higher fracture toughness, flexural strength and modulus than BMI/DBA. The improvement in the mechanical property for PBI film interleaved BMI/DBA system is mainly attributed to the combined effects of the effective energy dissipation of the sandwich structure and the good interfacial bonding between PBI film and the matrix. Due to the high thermal stability of PBI, the effective thermal insulation and electromagnetic field barrier of PBI film in the sandwich structure and the increase of the reacted CC in resin system, PBI film interleaved BMI/DBA shows better thermal property, much higher flame retardancy and lower dielectric constant compared to BMI/DBA. In addition, when the same amount of PBI is applied, BMI/DBA interleaved with PBI film exhibits much better comprehensive properties than BMI/DBA with PBI particles for the sandwich structure. POLYM. COMPOS., 39:4569–4580, 2018. © 2017 Society of Plastics Engineers

Membrane Evaporation for Energy Saving in CO2 Chemical Absorption Process Using a Polybenzimidazole Film: Mass and Heat Transfer

Intensive energy consumption remains a major challenge for the commercial application of CO2 chemical absorption. In this study, a membrane evaporation system based on PBI film was proposed for recovering latent heat from the hot lean CO2 solution in order to reduce the energy penalty during CO2 capture process. The effects of key operational parameters (i.e., evaporation temperature, sweeping gas flow rate, and liquid flow rate) were systematically investigated. It was found that both vapor flux and recovered heat flux had exponential increases when the evaporation temperature increased. Sweeping gas flow rate and liquid flow rate had limited effects on both mass and heat transfer in the membrane evaporation process. The PBI film showed good stability during a 14 days’ duration experiment. Reducing the membrane thickness can significantly improve the membrane evaporation performance. From the viewpoint of energy evaluation, when the evaporation mass reached 10 g/kg solution, the regeneration energy consu...

Flexible Supercapacitors Based on Solid Ion Conducting Polymer with High Mechanical Strength

Mechanical strength is crucial to flexible supercapacitors during their practical usage. In this work, polybenzimidazole with a high tensile strength of ∼100 MPa, an anion (or proton) conducting polymer electrolyte when doped with KOH (or H3PO4), was employed to fabricate highly robust and flexible supercapacitors. The polybenzimidazole film was integrated with activated carbon electrodes coated on graphite paper. These flexible supercapacitors exhibited low equivalent series resistance and good cycling stability of capacitance retention above 90% after 10000 cycles. Under mechanical deformations of bending, twisting, and rolling as well as a repeated bending test, the electrochemical performance of the flexible supercapacitors was well maintained, demonstrating good flexibility. The integration design showed better reliability against mechanical damage. It is an advantage for flexible supercapacitors with high energy density in mass production especially for devices based on KOH doped polybenzimidazole. This work suggests that polybenzimidazole based ion conducting polymer electrolytes are very promising for developing highly robust flexible supercapacitors in future practical applications.

Polymer film-based optical access to enclosed gas: demonstration of H2O absorption tomography

We demonstrate the use of a film to enable optical access to enclosed gases. We use absorption tomography to image H2O in a 101.6-mm-diameter duct with 2-mm spatial resolution. Considering the central 94 mm, the standard deviation of the image is 1.6 %, and the average mole fraction error is −0.008 %. A polybenzimidazole film is identified to be a candidate for extending the technique to enable NH3 imaging in a diesel aftertreatment system.