3D graphene has been explored as an important material and catalyst for many applications. However, it is still a challenge to tune the shape of 3D graphene sheets. Herein, it is demonstrated that the shapes of 3D graphene sheets, which were synthesized from the reaction between Li2O and CO, are strongly dependent on the particle size of Li2O. When Li2O particle size was very small (about 400 nm), the formed graphene sheets possessed a granulated shape. However, as Li2O particle size increased, the shape of the synthesized graphene sheets changed to flower-structure and then to honeycomb-structure. Furthermore, the shape change of graphene from the granulated to the honeycomb-structured can increase its electro-catalytic efficiency as a counter electrode catalyst for dye-sensitized solar cells (DSSCs). (C) 2016 Elsevier B.V. All rights reserved.