3D sponge nitrogen doped graphene (NG) was prepared economically from waste polyethylene-terephthalate (PET) bottles mixed with urea at different temperatures using green approach via a novel one-step method. The effect of temperature and the amount of urea on the formation of NG was investigated. Cyclic voltammetry and impedance spectroscopy measurements, revealed that nitrogen fixation, which affects the structure and morphology of prepared materials improve the charge propagation and ion diffusion. The prepared materials show outstanding performance as a supercapacitor electrode material, with the specific capacitance going up to 405 F g−1 at 1 A g−1. An energy density of 68.1 W h kg−1 and a high maximum power density of 558.5 W kg−1 in 6 M KOH electrolytes were recorded for the optimum sample. The NG samples showed an appropriate cyclic stability with capacitance retention of 87.7% after 5000 cycles at 4 A g−1 with high charge/discharge duration. Thus, the prepared NG herein is considered to be promising, cheap material used in energy storage applications and the method used is cost-effective and environmentally friendly method for mass production of NG in addition to opening up opportunities to process waste materials for a wide range of applications.

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Organic–inorganic nanocomposite membranes for potential application in direct borohydride fuel cells (DBFCs) are formulated from sulfonated poly(vinyl alcohol) (SPVA) with the incorporation of (PO4-TiO2) and (SO4-TiO2) nanotubes as doping agents. The functionalization of PVA to SPVA was done by using a 4-sulfophthalic acid as an ionic crosslinker and sulfonating agent. Morphological and structural characterization by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) confirmed the successful synthesis of the doping agents and their incorporation into the polymer. The influence of PO4-TiO2 and SO4-TiO2 doping and their content on the physicochemical properties of the nanocomposite membranes was evaluated. Swelling degree and water uptake gradually reduced to 7% and 13%, respectively, with increasing doping agent concentration. Ion exchange capacity and ionic conductivity of the membrane with 3 wt.% doping agents were raised 5 and 7 times, respectively, compared to the undoped one. The thermal and oxidative stability and tensile strength also increased with the doping content. Furthermore, lower borohydride permeability (0.32 × 10−6 cm2 s−1) was measured for the membranes with higher amount of inorganic doping agents when compared to the undoped membrane (0.71 × 10−5 cm2 s−1) and Nafion®117 (0.40 × 10−6 cm2 s−1). These results pave the way for a green, simple and low-cost approach for the development of composite membranes for practical DBFCs.

Developing low cost and highly active fuel cell is one of the high-priority research directions for fuel cell commercialization, whereas durable electrodes and electrolyte membranes are keys for its optimization. Herein, a novel nanocomposite electrolyte membranes for direct methanol fuel cell were prepared from eco-friendly polymer blend composed of poly(vinyl alcohol) (PVA) and iota carrageenan (IC). Sulfated titania (SO4TiO2) nanotubes are synthesized by impregnation–calcination method and incorporated as doping agents into the polymer matrix with different percentage ranged between 1 wt% and .5 wt%. The PVA/IC/SO4TiO2 nanocomposite membranes exhibited reduction in water and methanol uptake compared to that of undoped membrane, while the thermal properties and oxidative stability increased as the doping agent content increased. Methanol permeability of PVA/IC/[Formula: see text]-TiO2-7.5 membrane was 0.62 × 10−7 cm2 s−1, which is 43 times lower than Nafion 117 (26.9 × 10−7 cm2 s−1). Furthermore, it was noticed that the ion exchange capacity and mechanical properties of the nanocomposite membranes are higher than that of Nafion 117.

A novel promising strategy for the mass production of N-doped graphene (NG) provided with newly proposed mechanistic insights into the grown NG structure.