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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]

Polyacrylonitrile and polyheteroarylenes, such as polybenzimidazole (PBI) and a polymer of intrinsic microporosity (PIM-1), have been employed to prepare nanoporous electrospun carbon nanofiber (CNF)-based materials for high-temperature proton-exchange (or polymer-electrolyte) membrane (HT-PEM) fuel cells. The nanoporous CNF mats are obtained by Nanospider (needle-free) electrospinning method from polymer solution followed by pyrolysis at 1500 °C to form nanoporous electrospun polymer nanofiber self-supporting mats with micropores (D < 2 nm) and mesopores (D 2–50 nm). The nanoporous CNF samples are extensively characterized by N2 and CO2 adsorption applying the BET, BJH, Dubinin–Radushkevich (DR), NLDFT, and GCMC methods, CO2 uptake, Raman spectroscopy, elemental analysis, electrical conductivity, electron microscopy, and XPS. The role of the polymer precursor on the obtained values of specific surface area (SSA) and volume for micro- and mesopores is presented and discussed. The PBI-based CNF material reaches a micropore SSA of 919 m2 g–1 and CO2 uptake of 4.0 mmol g–1 derived from CO2 adsorption (273 K) data, and a micropore SSA of 873 m2 g–1 according to the t-method derived from N2 adsorption data. Close values confirm higher accessibility of micropores compared with the case of PIM-based CNF, where the micropore SSA values derived from CO2 and N2 adsorption data are different and indicate the partial inaccessibility of micropores for low-temperature nitrogen adsorption (77 K). Platinum-decorated CNF mats are successfully tested as electrodes for HT-PEM fuel cells, showing the feasibility of using the mats as cathodes; nevertheless, further optimization is required. For CNF anodes, the HT-PEM fuel cell performance reaches 0.69 V at 0.2 A cm–2 and 0.53 W cm–2 at 1.4 A cm–2 which permits the use of the Pt/CNF mats as anodes. [ABSTRACT FROM AUTHOR]

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]

Different polyheteroarylenes, such as m-polybenzimidazole, polyphenylene oxide, polymer of intrinsic microporosity (PIM-1) and poly(N-phenylene-benzimidazole) were electrospun to obtain self-supporting polymer nanofiber mats. The mats after heat treatment, which contains stabilization in air at 250-350 °C and pyrolysis at 900-1000 °C under vacuum, convert into carbon nanofiber paper, a material which is suitable for Pt nanoparticle deposition. The possibility of usage of the obtained carbonized nanocomposites as entire gas diffusion electrodes for high temperature polymer electrolyte membrane fuel cell is shown. [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]