Abstract
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.
Highlights
There are numerous methods to synthesize nitrogen doped graphene, which can be categorized into two kinds of methods: direct synthesis such as chemical vapor deposition (CVD), arc-discharge, segregation growth, solvothermal methods, and post treatment such as hydrazine hydrate, thermal and plasma treatments[5,8]
In order to prove the presence of nitrogen doped in graphene structure, an elemental analysis was conducted on the dried product with X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR)
The results suggest that the N atoms are covalently bonded networks of graphene and there are two possible ways; the first suggested way is via chemical reactions of the urea with surface functional groups in the intermediate carbon structure formed during decomposition of PET and subsequent thermal transformations of the formed compound[1]
Summary
Electrochemical capacitors (ECs) are considered as one of the most promising energy storage technologies responding to the increasing demand of the clean energy related technologies and applications such as portable/ mobile electronics, electrical vehicles, or other storage systems based on sources like windmills and solar cells. Bonding configuration changes from sp[2] to sp[3] and less oxygen functional groups are present in grapheme, that in turn enhances the capacitive behavior because the oxygen functional groups would impede the migration of electrolyte ions into micropores and as a result reduced the effective pore volume of the graphenic materials. Both raw materials are low cost and are manufactured in large quantities.
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