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The efficient use of renewable energy sources requires development of new electrocatalytic materials for electrochemical energy storage systems, particularly fuel cells. To increase durability of high temperature polymer electrolyte fuel cell (HT-PEMFC), Pt/carbon black based catalysts should be replaced by more durable ones, for example Pt/carbon nanofibers (CNF). Here, we report for the first time the quantitative ascorbic acid assisted deposition of Pt onto electrospun polyacrylonitrile-based CNF composite materials. The effect of their subsequent post-treatment at various temperatures (250 and 500 °C) and media (vacuum or argon-hydrogen mixture) on the Pt/C catalyst morphology is investigated. All obtained samples are thoroughly studied by high resolution electron microscopy, and Pt electrochemically active specific surface area was evaluated by cyclic voltammetry. [ABSTRACT FROM AUTHOR]

High-temperature polymer-electrolyte membrane fuel cells (HT-PEMFCs) are a very important type of fuel cells since they operate at 150–200 °C, making it possible to use hydrogen contaminated with CO. However, the need to improve the stability and other properties of gas-diffusion electrodes still impedes their distribution. Self-supporting anodes based on carbon nanofibers (CNF) are prepared using the electrospinning method from a polyacrylonitrile solution containing zirconium salt, followed by pyrolysis. After the deposition of Pt nanoparticles on the CNF surface, the composite anodes are obtained. A new self-phosphorylating polybenzimidazole of the 6F family is applied to the Pt/CNF surface to improve the triple-phase boundary, gas transport, and proton conductivity of the anode. This polymer coating ensures a continuous interface between the anode and proton-conducting membrane. The polymer is investigated using CO2 adsorption, TGA, DTA, FTIR, GPC, and gas permeability measurements. The anodes are studied using SEM, HAADF STEM, and CV. The operation of the membrane–electrode assembly in the H2/air HT-PEMFC shows that the application of the new PBI of the 6F family with good gas permeability as a coating for the CNF anodes results in an enhancement of HT-PEMFC performance, reaching 500 mW/cm2 at 1.3 A/cm2 (at 180 °C), compared with the previously studied PBI-O-PhT-P polymer. [ABSTRACT FROM AUTHOR]

Polymer of intrinsic microporosity (PIM-1) is characterized by a developed microporous structure. Needle-free Nanospider™ electrospinning of the PIM-1 solution with subsequent pyrolysis either under vacuum or in argon-hydrogen medium (7 vol% H 2) at 900–1200 °C results in PIM-1 based carbon nanofibers (CNF) self-supporting mats. The samples were thoroughly characterized by N 2 and CO 2 adsorption using the BET, BJH, Dubinin-Radushkevich (DR), NLDFT and GCMC methods, CO 2 uptake, and by Raman spectroscopy, elemental analysis, electrical conductivity, SEM. Since the N 2 adsorption is found to be inapplicable, the presence of microporosity in the CNF is confirmed by CO 2 adsorption (273 K) by the DR, NLDFT and GCMC methods. The CNF reach micropore specific surface area of 919 m2 g−1, micropore volume of 0.257 cm3 g−1 and CO 2 uptake of 4.01 mmol g−1, which is higher than for initial PIM-1. Pt/PIM-1 CNF self-supporting mat, was successfully tested as anode for HT-PEM fuel cell. Carbon dioxide adsorption method unveils PIM-1 carbon nanofiber microporosity exceeding PIM-1 microporosity. [Display omitted] • Electrospun PIM-1 carbon nanofibers are mostly ultramicroporous. • Microporosity characteristics of PIM-1 CNF exceed the ones for PIM-1. • PIM-1 CNF specific surface area reaches 919 m2 g−1 • CO 2 uptake for PIM-1 CNF is higher than for PIM-1. • Pt/PIM-1 CNF mats can be used as anodes in HT-PEM fuel cell. [ABSTRACT FROM AUTHOR]

Development of new microporous organic polymers attracts significant attention due to a wide scope of promising applications. In addition, the synthesis of soluble, non-crosslinking polymers of high surface area and uniform microporosity is very challenging, and the methods for soluble microporous polymers formation are rather limited. In this work, we report a new approach to construct porous polyphenylenes which employs the Diels–Alder polycondensation of multifunctional ethynyl-containing monomers of different spatial architecture with bis(cyclopentadienone)s. The resulting polymers were soluble in common organic solvents, and their structure and properties were assessed by NMR, TGA, DSC, and SEC studies. The polymers demonstrated a specific surface area up to 751 m2·g−1 and ultramicroporous (pore size ≤ 0.6 nm) structure. N2 and CO2 adsorption–desorption data revealed that porosity parameters, e.g., specific surface area and pore sizes, can be tuned selectively by varying the type of monomers and reaction conditions. [ABSTRACT FROM AUTHOR]

AB-polybenzimidazole (ABPBI) dissolution kinetics in an eco-friendly complex acid-free solvent based on dimethyl sulfoxide (DMSO), methanol and KOH, and the rheological behavior of their solutions are investigated. The optimal component ratio of solvent providing the complete ABPBI dissolution is determined. Methanol containing dissolved KOH contributes to the creation of a single-phase superbasic medium, which accelerates and improves the polymer solubility in a mixture with DMSO, significantly reducing the viscoelasticity of the resulting solution. The optimum methanol content is up to 60 wt.% related to DMSO. The polymer dissolution rate increases by 5 times in this composition. It found the polymer concentration of 9% is close to the dissolution limit due to the strong solution structuring, which is probably associated with an increase in the amount of water released during the KOH-methanol-DMSO interactions. As a result, the conditions for obtaining high concentrated solutions in a complex, mainly organic solvent for fiber spinning are developed. The viscoelastic properties of solutions are measured in the concentration range of 1–9% at temperatures of 20–50 °C. The flow activation energy for 7 and 9% solutions decreases by 1.5 and 2.3 times, respectively, as the content of methanol in the complex solvent increases from 10 to 60%. [ABSTRACT FROM AUTHOR]

High strength flame-resistant semi-ladder fibers of the "Lola" family (PNBI) have been obtained by an acid-free and more environmentally friendly method with controlled heating of precursor fibers in an inert atmosphere. The suggested two-step method consists in preparation of a prepolymer (PANI-O) in N-methylpyrrolidone. The prepared PANI-O dopes were additionally modified by introducing a certain part of a non-solvent (ethanol) to smooth the interdiffusion mass-transfer and prepare defectless precursor fibers. A detailed study of the thermal behavior of the PANI-O fibers by DSC and TGA shows that the maximum exothermic effect is observed at 320–370 °C, associated with formation of a ladder structure, i.e., transformation of the PANI-O into the PNBI-O. As a result, after the heat treatment, the flame-resistant PNBI "Lola" family fibers were obtained with an oxygen index of up to 83, tensile strength of ∼500 MPa, relative elongation of ∼5% and elastic modulus of ∼12 GPa. Flame-resistant semi-ladder PNBI fibers were obtained by acid-free environmentally friendly way through PANI-O prepolymer stage. [Display omitted] • PNBI fibers were obtained by an environmentally friendly way. • PNBI fibers were obtained through a PANI-O prepolymer stage. • Ethanol addition leads to defectless pre-polymer fibers by dry-wet spinning. • LOI of 83 for the H 3 PO 4 impregnated PNBI fibers was obtained. • Outstanding mechanical properties were recorded for the obtained PNBI fibers. [ABSTRACT FROM AUTHOR]

A series of model experiments were carried out on drops of poly-(o-aminophenylene)naphthoylenimide (PANI-O) solutions in N-methyl-2-pyrrolidone (NMP) surrounded by a coagulant of different compositions as starting points of defect-free fibers spinning by the wet method. An influence of compositions of dopes and multicomponent coagulants on the diffusion kinetics and drop morphology during coagulation has been investigated. It is shown that the defining parameters of the coagulation process are viscoelastic properties of the polymer solution and the diffusion activity of the coagulant, meaning not only the rate of coagulation but also the presence/absence of macro defects in the resulting fiber. The optimal morphology of as-spun fibers is obtained by coagulation of solution in a three-component mixture containing solvent and two precipitants of different activity (water and ethanol). The chosen coagulating mixture was used for the fiber spinning of PANI-O with different molecular weights dopes, and fibers with sufficiently high strength (~250 MPa), moduli (~2.1 MPa), and elongation at break (50%) were obtained. [ABSTRACT FROM AUTHOR]

Semi-ladder high-molecular polynaphthoylenebenzimidazoles (PNBI) were synthesized through polyaminonaphtoyleneimide (PANI) formation and thermal cyclization at 350 °C. The structures of PANIs and PNBIs were confirmed by NMR, GPC and FTIR. Polymer films were obtained from PANI pre-polymer by solution-cast technique. After thermal cyclization, the PNBI films exhibit excellent mechanical properties: tensile strength of 95–174 MPa, Young's modulus of 1.5–2.4 GPa and elongation at break of 10–50%. The PNBIs are located near the upper bound of the 1991 Robeson diagram for O 2 /N 2 , H 2 /N 2 and H 2 /CH 4 gas pairs, while the PNBI with a hexafluoroisopropylidene bridge (PNBI-4) overcomes it for CO 2 /CH 4 , approaching the upper bound of the 2008 Robeson diagram. A peculiarity of the synthesized polymers is lower gas diffusion coefficients and higher gas solubility coefficients, which are close to polypyrrolones and PIM family polymers. The higher PNBI diffusion selectivity identifies them as organic molecular sieves, as confirmed by the specific surface area of PNBI-4, which is close to PIM-1. The data obtained allows to classify the studied PNBIs as unexpected PIM relatives. The synthesized PNBIs are polymer molecular sieves and, unexpectedly, belong to the polymer of intrinsic microporosity family. [Display omitted] • The PNBI gas transport properties have been obtained. • The studied PNBIs lie on the upper bounds of the 1991 Robeson diagrams. • PNBI-4 is higher than the upper bound on the 1991 Robeson diagram for CO 2 /CH 4. • PNBI-4 is approaching the upper bound of the 2008 Robeson diagram for CO 2 /CH 4. • PNBI-4 possesses a microporous structure similar to the one of PIM-1. [ABSTRACT FROM AUTHOR]

Here we report new porous carbon materials obtained by 3D printing from photopolymer compositions with zinc- and nickel-based metal–organic frameworks, ZIF-8 and Ni-BTC, followed by high-temperature pyrolysis. The pyrolyzed materials that retain the shapes of complex objects contain pores, which were produced by boiling zinc and magnetic nickel particles. The two thus provided functionalities—large specific surface area and ferromagnetism—that pave the way towards creating heterogenous catalysts that can be easily removed from reaction mixtures in industrial catalytic processes. [ABSTRACT FROM AUTHOR]

The most environmentally safe method of PBI synthesis is reported and applied in the high proton conductivity membrane production for high temperature polymer electrolyte membrane fuel cell. [Display omitted] • Breakthrough PBI synthesis for HT-PEMFC proton-conducting membrane is suggested. • The environmentally safe method of PBI synthesis is developed. • The membrane was successfully tested in HT-PEM fuel cell. • Extremely low hydrogen crossover through the membrane at 180 °C was registered. The article presents a new environmentally safe synthetic approach towards durable polybenzimidazole proton-conducting membrane via polyamidation at ambient conditions and subsequent thermal heterocyclization of films cast from reaction solution followed by phosphoric acid doping. The method avoids exhausts, acid waste and inorganic salts, compared with the existing methods and technologies, allowing to minimize the negative environmental impact related to the process. The membrane possesses an excellent proton conductivity of 105 mS cm−1 and good mechanical properties and has been successfully tested in high temperature polymer electrolyte membrane fuel cells. An extremely low hydrogen crossover through the membrane of 0.040 mA cm−2 at 180 °C has been registered compared with quite high 4–5 mA cm−2 for Celazole® m -PBI. [ABSTRACT FROM AUTHOR]