Graphene-based electrodes were deposited onto metallic or gold-coated polymer substrates. The technique that we developed allows for the chemical transformation and simultaneous deposition of graphene oxide (GO) and GO-NiO nanoparticles. Nitrogen inclusion into the structure of GO was achieved through the addition to the irradiated aqueous target dispersions containing the nanoentities, GO platelets and NiO nanoparticles, nitrogen containing organic compounds (ammonia, urea, or melamine). The obtained flexible electrodes reveal high electrochemical charge storage performance (Figure) as well as outstanding long-term charge–discharge stability.
Addition of melamine to the graphene oxide-NiO dispersions leads to the synthesis of the electrodes with the highest energy storage performance. Melamine, as nitrogen containing precursor, leads to the formation of pyrrolic / amine, graphitic quaternary, and pyridinic nitrogen functional groups. Amine groups and graphitic nitrogen doping of GO are known to reduce the intrinsic resistance of graphene platelets and thus, ensure better electron transfer through the active material, improving the electrodes’ capacitive performance. Moreover, graphitic and pyridinic nitrogen exhibit large dipole moments that greatly enhance the wettability of graphene materials in aqueous electrolyte solutions, leading to capacitance enhancement. Besides, pyridinic and pyrrolic nitrogen groups are electrochemically active, participating in redox reactions.
The developed fabrication method is cost-effective, fast, and environmentally friendly, characterized by an enormous versatility for the growth of functional nanocomposite coatings. Moreover, the work opens up new possibilities for the synthesis and deposition of new compounds, through the light induced chemical reactions taking place during the irradiation of organic materials.
Ángel Pérez del Pino,1 Andreu Martınez Villarroya,1 Alex Chuquitarqui,1 Constantin Logofatu,2 Dino Tonti,1 Enikö György1
1 Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain
2 National Institute for Materials Physics, Romania
Reactive laser synthesis of nitrogen-doped hybrid graphene-based electrodes for energy storage
Journal of Materials Chemistry A, 6, 16074–16086 (2018)
(a) Areal and (b) volumetric capacitance of the deposited nitrogen doped reduced graphene oxide (GO) and transition metal oxide electrodes