Nanotechnology is providing new solutions and opportunities to ensure sustainable energy and environments for the future. Materials of nanofiberous morphology are attractive to solve numerous energy and environmental issues. Nanofibers can be effectively produced by electrospinning, which is a simple and low cost technique. In addition, electrospinning allows the production of nanofibers from various materials e.g. organics and inorganics in different configurations and assemblies. This is highly beneficial for energy devices, where inorganic materials especially metal oxides can be synthesized and electrospun, improving conducting and ceramic properties. Excitonic solar cells fabricated with aligned nanofiberous metal oxide electrodes provide higher solar–electric energy conversion efficiency, whereas fuel cells made with nanofiberous electrodes enable uniform dispersion of catalysts, and thus increase electrocatalytic activity to obtain higher chemical–electric energy conversion efficiency. The nanofibers used in filtration membranes for environmental remediation, minimize the pressure drop and provide better efficiency than conventional fiber mats. The large surface area-to-volume ratio of nanofiber membranes allows greater surface adsorption of contaminants from air and water, and increases the life-time of the filtration media. This review highlights the potential and application of electrospun nanofiberous materials for solving critical energy and environmental issues.

α-Fe₂O₃ nanorods are synthesized by electrospinning of polyvinylpyrrolidone (PVP)/ferric acetyl acetonate (Fe(acac)₃) composite precursors and subsequent annealing at 500 °C for 5 h. X-ray diffraction and Raman spectroscopy analyses confirm the formation of a hematite structure as the predominant phase. The electron microscopy studies show that the electrospun α-Fe₂O₃ nanorods are composed of agglomerates of nano-sized particles and the average diameter of the nanorods is found to be 150 nm. Li-storage and cycling properties are examined by galvanostatic cycling in the voltage range 0.005–3 V vs. Li at various current densities and it is complemented by cyclic voltammetry. The electrospun α-Fe₂O₃ nanorods exhibit a high reversible capacity of 1095 mA h g⁻¹ at 0.05 C, are stable up to 50 cycles and also show high rate capability, up to 2.5 C. The high rate capability and excellent cycling stability can be attributed to the unique morphology of the macroporous nanorods comprised of inter-connected nano-sized particles, thus making electrospun α-Fe₂O₃ a promising anode material for Li-ion batteries.

Hollow mesoporous one dimensional (1D) TiO₂ nanofibers are successfully prepared by co-axial electrospinning of a titanium tetraisopropoxide (TTIP) solution with two immiscible polymers; polyethylene oxide (PEO) and polyvinylpyrrolidone (PVP) using a core–shell spinneret, followed by annealing at 450 °C. The annealed mesoporous TiO₂ nanofibers are found to having a hollow structure with an average diameter of 130 nm. Measurements using the Brunauer–Emmett–Teller (BET) method reveal that hollow mesoporous TiO₂ nanofibers possess a high surface area of 118 m² g⁻¹ with two types of mesopores; 3.2 nm and 5.4 nm that resulted from gaseous removal of PEO and PVP respectively during annealing. With hollow mesoporous TiO₂ nanofibers as the photoelectrode in dye sensitized solar cells (DSSC), the solar-to-current conversion efficiency (η) and short circuit current (J_sc) are measured as 5.6% and 10.38 mA cm⁻² respectively, which are higher than those of DSSC made using regular TiO₂ nanofibers under identical conditions (η = 4.2%, J_sc = 8.99 mA cm⁻²). The improvement in the conversion efficiency is mainly attributed to the higher surface area and mesoporous TiO₂ nanostructure. It facilitates the adsorption of more dye molecules and also promotes the incident photon to electron conversion. Hollow mesoporous TiO₂ nanofibers with close packing of grains and crystals intergrown with each other demonstrate faster electron diffusion, and longer electron recombination time than regular TiO₂ nanofibers as well as P25 nanoparticles. The surface effect of hollow mesoporous TiO₂ nanofibers as a photocatalyst for the degradation of rhodamine dye was also investigated. The kinetic study shows that the hollow mesoporous surface of the TiO₂ nanofibers influenced its interactions with the dye, and resulted in an increased catalytic activity over P25 TiO₂ nanocatalysts.