Nanofibers are synthesized by electrospinning highly loaded water-based precursor-polymer hybrid solutions followed by thermal treatment to control crystal structure. Electrical conductivity and magnetic coercivity, as shown, are tested displaying independent magnetic and electrical property control from coercive to superparamagnetic and resistive to near-bulk conductivity at room temperature.

Hybrid carbon nanofibers (NFs) with extremely high Si loading (>65 wt %) are fabricated through the water‐based electrospinning of polyvinyl alcohol/Si nanoparticle (NP) solutions for Li‐ion battery anode applications. Our Si‐rich carbon (SRC) NFs show many facilitated charge‐transport features and increased activities because of the continuous one‐dimensional (1D) carbon backbone structure with dispersed Si NP domains. This leads to superior battery performance compared to that of bare silicon NPs. The presence of carbon as 1D NFs can not only mitigate the volume change of silicon but also avoid the formation of an unstable solid‐electrolyte interface on the surface of silicon. Our study, regarding the optimum combination of C and Si in the NFs for their improved electrochemical properties and battery performance, reveals that SRC NFs containing 72.8 wt % Si (27.2 wt % C) exhibit an adequate balance between the high energy capacity of Si NPs and the dimensional stability and effective charge transport of carbon NFs. This optimum Si/C ratio leads to an outstanding cycle life, which maintains 1076 mAh g−1 capacity normalized by the total electrode mass, and a Coulombic efficiency of about 99 % over 50 cycles. Such scalable SRC NFs produced through the water‐based spinning approach can offer a cost‐effective development for high‐performance battery anodes.

Electrospun nanofibers containing titanium dioxide (TiO2) were investigated as a self-detoxifying system consisting of polyacrylonitrile (PAN) and anatase TiO2 nanoparticles. Fibers were prepared by uniaxial and coaxial electrospinning to study the effect of nanoparticle placement on the detoxification activities of the photocatalyst. Coaxially spun fibers had the particles selectively placed in the sheath layer by electrospinning pure PAN solution and PAN/TiO2 solution as the core and sheath layer, respectively. Using scanning electron microscopy, X-ray microanalysis and X-ray photoelectron spectroscopy, it was confirmed that the coaxial approach resulted in the location of nanoparticles near the surface of the fibers compared to the uniform distribution obtained for uniaxial fibers. Photocatalytic activity of the fibers under ultraviolet irradiation was demonstrated by the degradation of aldicarb, as measured by high-performance liquid chromatography. In terms of degradation kinetics, the distribution density of TiO2 nanoparticles in the fiber surface region significantly affected the initial degradation rate, while the final decomposition amounts after 3 h did not differ significantly.

Monoaxial silica nanofibers containing iron species as well as coaxial nanofibers with a pure silica core and a silica shell containing high concentrations of iron nanocrystals were fabricated via electrospinning precursor solutions, followed by thermal treatment. Tetraethyl-orthosilicate (TEOS) and iron nitrate (Fe(NO(3))(3)) were used as the precursors for the silica and iron phases, respectively. Thermal treatments of as-spun precursor fibers were applied to generate nanocrystals of iron with various oxidation states (pure iron and hematite). Scanning electron microscopy (SEM), x-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to probe the fiber morphology and crystal structures. The results indicated that the size, phase, and placement of iron nanocrystals can be tuned by varying the precursor concentration, thermal treatment conditions, and processing scheme. The resulting nanofiber/metal systems obtained via both monoaxial and coaxial electrospinning were applied as catalysts to the alkaline hydrolysis of glucose for the production of fuel gas. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and bulk weight change in a furnace with residual gas analysis (RGA) were used to evaluate the performance of the catalysts for various ratios of both Fe to Si, and catalyst to glucose, and the oxidation state of the iron nanocrystals. The product gas is composed of mostly H(2) (>96 mol%) and CH(4) with very low concentrations of CO(2) and CO. Due to the clear separation of reaction temperature for H(2) and CH(4) production, pure hydrogen can be obtained at low reaction temperatures. Our coaxial approach demonstrates that placing the iron species selectively near the fiber surface can lead to two to three fold reduction in catalytic consumption compared to the monoaxial fibers with uniform distribution of catalysts.