Graphene-based materials with tailored nanostructures for energy conversion and storage

Intensive interest in graphene has centered on its unique 2D crystal lattice and remarkable properties that offer unique opportunities to address ever-increasing global energy demands. The past years have witnessed considerable advances in the fabrication of graphene-based materials and significant breakthroughs in advanced energy applications. In this Review, two methodologies for graphene production, namely, the bottom-up growth from hydrocarbon precursors and the top-down exfoliation of graphite (to graphene) and graphite oxide (to graphene oxide followed by reduction) are first summarized. The advantages and disadvantages of these methods regarding their accessibility, scalability, graphene quality, and inherent properties are compared. Particular attention is concentrated on tailored nanostructures, electronic properties, and surface activities of these intriguing materials. The preparation of graphene-based composites containing a wide range of active constituents (e.g., transition metals, metal oxides, and conducting polymers) by in-situ hybridization and ex-situ recombination is also discussed with an emphasis on their microstructures and hybrid architectures. This Review is devoted largely to current developments of graphene and its derivatives and composites in energy conversion (i.e., polymer solar cells, dye-sensitized solar cells, perovskite solar cells, and fuel cells) and energy storage (i.e., lithium-ion batteries and supercapacitors) on the basis of their intrinsic attributes in improving photovoltaic and electrochemical performance. By critically evaluating the relationship between the nanostructures and the device performance, we intend to provide general guidelines for the design of advanced graphene-based materials with structure-to-property tailored toward specific requirements for targeted energy applications. Lastly, the potential issues and the perspective for future research in graphene-based materials for energy applications are also presented. By summarizing the current state-of-the-art as well as the exciting achievements from laboratory research, this Review aims to demonstrate that real industrial applications of graphene-based materials are to be expected in the near future. (1346 references).