The green one-step electrodeposition of oxygen-functionalized porous g-C3N4 decorated with Fe3O4 nanoparticles onto Ni-foam as a binder-free outstanding material for supercapacitors

In this study, the binder-free high-performance nanocomposite of Fe3O4/oxygen-functionalized g-C3N4 was fabricated through a one-pot electrophoretic-electrochemical (EP-EC) process. In this process, Fe3O4 nanoparticles were in situ nucleated through a two-step electrochemical-chemical (EC) mechanism on oxygen-functionalized g-C3N4 (O-g-C3N4) sheets electrophoretically embedded on a Ni-foam support. Also, pristine Fe3O4 nanoparticles and O-g-C3N4 sheets were fabricated on Ni foam (i.e. Fe3O4/Ni foam and O-g-C3N4/Ni foam) via the EC and EP processes, respectively. The prepared powders/electrodes were fully characterized through XRD, FT-IR, BET/BJH, Raman spectroscopy, TGA/DSC, FE-SEM and TEM. The morphological observations confirmed the nucleation and growth of Fe3O4 particles on the porous O-g-C3N4 sheets in the structure of the Fe3O4@O-g-C3N4/Ni foam electrode. The formation mechanisms of the pristine Fe3O4 particles, pristine O-g-C3N4 sheets and their nanocomposite on the Ni-foam support were explained based on the electrophoretic-electrochemical deposition processes. Electrochemical evaluation by galvanostatic charge–discharge (GCD) indicated that the fabricated Fe3O4@O-g-C3N4/Ni foam delivered a specific capacitance of 710 F g−1 at 0.5 A g−1 and capacity retention of 94.6% and 80.15% after 8000 GCD cycling at the current load of 0.5 and 3 A g−1, whereas the pristine Fe3O4/NF showed a specific capacitance of 277 F g−1 at 0.5 A g−1 and capacity retentions of 82.4% and 48.9% only, under similar GCD conditions, respectively. These findings prove the superior synergism between the Fe3O4 nanoparticles and oxygen-functionalized g-C3N4 sheets in the composite structure.