Due to its unique chemical and physical properties, graphene is a potential candidate for broad applications including energy conversion and storage. During the past several years, we have investigated applications of graphene as counter electrode for dye-sensitized solar cells, electron and hole transport layers in organic solar cells, catalyst and catalyst support for methanol/ethanol oxidation and oxygen reduction, and electrodes for supercapacitors. In this report, we will discuss how to tailor structures of graphene to fit their broad applications. The findings in the study above will provide information for design, synthesis and applications of graphene-based nanocomposites for energy conversion and storage.