In this article, we provide an overview of recent progress in toughening and damage self‐healing of polymer–matrix composites (PMCs) reinforced with electrospun or solution‐blown nanofibers at interfaces with an emphasis on the innovative processing techniques and toughening and damage self‐healing characterization. Because of their in‐plane fiber architecture and layered structure, high‐performance laminated PMCs typically carry low interfacial strengths and interlaminar fracture toughnesses in contrast to their very high in‐plane mechanical properties. Delamination is commonly observed in these composite structures. Continuous polymer and polymer‐derived carbon nanofibers produced by electrospinning, solution blowing, and other recently developed techniques can be incorporated into the ultrathin resin‐rich interlayers (with thicknesses of a few to dozens of micrometers) of these high‐performance PMCs to form nanofiber‐reinforced interlayers with enhanced interlaminar fracture toughnesses. When incorporated with core–shell healing‐agent‐loaded nanofibers, these nanofiber‐richened interlayers can yield unique interfacial damage self‐healing. Recent experimental investigations in these topics are reviewed and compared, and recently developed techniques for the scalable, continuous fabrication of advanced nanofibers for interfacial toughening and damage self‐healing of PMCs are discussed. Developments in the near future in this field are foreseen. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2225–2237, 2013

This paper reports the synthesis and electrochemical performance of carbon nanofibers (CNFs) surface-grown with carbon nanotubes (CNTs) and nanostructured polyaniline (PANI) films, i.e., PANI/CNT/CNF, for use as a high-performance electrode material of pseudosupercapacitors. The PANI/CNT/CNF films were synthesized via in situ polymerization of aniline onto the surface of CNT-coated CNFs. The CNT-coated CNFs were prepared via electrospinning continuous polyacrylonitrile (PAN) nanofibers, followed by controlled carbonization and CNT growth. The morphology and microstructure of the PANI/CNT/CNF were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The electrochemical properties of the novel nanofiber films were characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge/discharge (GCD) in a 1 M aqueous H₂SO₄ solution as electrolyte. This unique porous nanofibrous structure exhibited low equivalent series resistance (ESR) and interfacial charge-transfer resistance (R_ct) of 1.46 Ω and 0.55 Ω, respectively. Supercapacitors based on the present PANI/CNT/CNF electrodes behaved as with high specific capacitance of ∼503 F g⁻¹ at a current density of 0.3 A g⁻¹ and ∼471 F g⁻¹ (only 6% decrease) at 3 A g⁻¹. The maximum energy and power densities of ∼70 W h kg⁻¹ and ∼15 kW kg⁻¹ were achieved. In addition, over 92% of the initial capacitance was retained after 1000 charge/discharge cycles at a current density of 15 A g⁻¹. The results of the present experimental study suggested that such a unique multifunctional nanofibrous material can be utilized for developing high-performance electrochemical energy storage devices such as pseudosupercapacitors, battery–supercapacitor hybrids, etc.

Polymer electrolyte membrane fuel cells (PEMFCs) expect a promising future in addressing the major problems associated with production and consumption of renewable energies and meeting the future societal and environmental needs. Design and fabrication of new proton exchange membranes (PEMs) with high proton conductivity and durability is crucial to overcome the drawbacks of the present PEMs. Acid-doped polybenzimidazoles (PBIs) carry high proton conductivity and long-term thermal, chemical, and structural stabilities are recognized as the suited polymeric materials for next-generation PEMs of high-temperature fuel cells in place of Nafion^® membranes. This paper aims to review the recent developments in acid-doped PBI-based PEMs for use in PEMFCs. The structures and proton conductivity of a variety of acid-doped PBI-based PEMs are discussed. More recent development in PBI-based electrospun nanofiber PEMs is also considered. The electrochemical performance of PBI-based PEMs in PEMFCs and new trends in the optimization of acid-doped PBIs are explored.

A nickel incorporated carbon nanotube/nanofiber composite (Ni-CNT-CNF) was used as a low cost alternative to Pt as counter electrode (CE) for dye-sensitized solar cells (DSCs). Measurements based on energy dispersive X-rays spectroscopy (EDX) showed that the majority of the composite CE was carbon at 88.49 wt%, while the amount of Ni nanoparticles was about 11.51 wt%. Measurements based on electrochemical impedance spectroscopy (EIS) showed that the charge transfer resistance (R_ct) of the Ni-CNT-CNF composite electrode was 0.71 Ω cm², much lower than that of the Pt electrode (1.81 Ω cm²). Such a low value of R_ct indicated that the Ni-CNT-CNF composite carried a higher catalytic activity than the traditional Pt CE. By mixing with CNTs and Ni nanoparticles, series resistance (R_s) of the Ni-CNT-CNF electrode was measured as 5.96 Ω cm², which was close to the R_s of 5.77 Ω cm² of the Pt electrode, despite the significant difference in their thicknesses: ∼22 μm for Ni-CNT-CNF composite, while ∼40 nm for Pt film. This indicated that use of a thick layer (tens of microns) of Ni-CNT-CNF counter electrode does not add a significant amount of resistance to the total series resistance (R_s−tot) in DSCs. The DSCs based on the Ni-CNT-CNF composite CEs yielded an efficiency of 7.96% with a short circuit current density (J_sc) of 15.83 mA cm⁻², open circuit voltage (V_oc) of 0.80 V, and fill factor (FF) of 0.63, which was comparable to the device based on Pt, that exhibited an efficiency of 8.32% with J_sc of 15.01 mA cm⁻², V_oc of 0.83, and FF of 0.67.