Self-assembled graphene quantum dots-Co3O4 nanocomposite for highly efficient oxygen evolution reaction electrocatalyst

A novel kind of self-assembled graphene quantum dots-Co 3 O 4 (GQDs-Co 3 O 4 ) nanocomposite was successfully manufactured through a hydrothermal approach and used as an extremely effectual oxygen evolution reaction (OER) electrocatalyst. The characterization of morphology with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that Co 3 O 4 nanosheets combined with graphene quantum dots (GQDs) had a new type of hexagonal lamellar self-assembly structure. The GQDs-Co 3 O 4 electrocatalyst showed enhanced electrochemical catalytic properties in an alkaline solution. The start potential of the OER was 0.543 V (vs SCE) in 1 M KOH solution, and 0.577 V (vs SCE) in 0.1 M KOH solution correspondingly. The current density of 10 mA cm −2 had been attained at the overpotential of 321 mV in 1 M KOH solution and 450 mV in 0.1 M KOH solution. Furthermore, the current density can reach 171 mA cm −2 in 1 M KOH solution and 21.4 mA cm −2 in 0.1 M KOH solution at 0.8 V. Moreover, the GQDs-Co 3 O 4 nanocomposite also maintained an ideal constancy in an alkaline solution with only a small deterioration of the activity (7%) compared with the original value after repeating potential cycling for 1000 cycles.