▎ 摘　　要

Herein, 3D graphene ornamented with CoO nanoparticles efficaciously synthesized by simple ion exchange strategy, followed by chemical reduction and thermal treatment. The graphene shows three-dimensional lamellae which are composed of a few layers of graphene. The ultrathin graphene lamella offers the large surface area for cobalt oxide particles to deposit over its surface. Cobalt oxide particles of different size and shape which is accumulated on the surface of graphene layers provide large active sites for OER and HER. The as-prepared composite acts an efficient bifunctional electmcatalyst for OER and HER in 1 M KOH solution. The as-prepared CG-3 electrocatalyst required overpotential of 1.6 V and 0.36 V (vs RHE) to deliver the current density of 10 mA cm(-2) for OER and HER respectively. The CG-3 electrocatalyst exhibits Tafel slope value of 62 and 104 mV dec(-1) for OER and HER respectively. The CG-3 also shows good stability for 4 h with low R-ct for OER and HER.