Fig. 1. SEM images of (a) Pristine GF, (b) Hydrothermal GF, (c) Heat GF, (d) H2 GF
Fig. 2. SEM image of (a) H2 GF. EDS images show surface elements of H2 GF (b) C, (c) O, (d) Co
Fig. 3. XRD patterns of each GF (a) Hydrothermal GF CoO3, Heat GF Co3O4, H2 GF α-Co. XRD reference data (b) CoO3 (ICSD : 98-009-3854), Co3O4 (ICSD : 98-006-9375), α-Co (ICSD : 98-005-3805)
Fig. 4. Cyclic voltammograms of each GF for V (IV)/V (V) redox couple in 0.1 M V (IV) + 3 M H2SO4 electrolyte (a) H2 GF treated at various temperature, (b) H2 GF treated at various time, (c) Pristine GF, Hydrothermal GF, Heat GF, H2 GF, (d) Various scan rates of Pristine GF, (e) Various scan rates of H2 GF, (f) Peak current density vs square root scan rate of Pristine GF and H2 GF
Table 1. Electrochemical performance of GF for V (IV)/V (V) redox couple in 0.1 M V (IV) + 3 M H2SO4 electrolyte
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