Heteroatom doped graphene engineering for energy storage and conversion

Heteroatom-doped graphene and its derived layered materials play a substantial role in several emerging science fields, demonstrating great potential for implementation in new devices and for improving the performance of existing technologies. A wide variety of strategies have been applied for the controlled synthesis and for achieving the intended doping/co-doping levels in the carbon network of graphene-based materials. Precise and reproducible doping is crucial for altering the Fermi energy level and to tune the band gap according to the desired device/application. Heteroatom-doped and co-doped graphene-based materials (n-type and p-type doping) have been synthesized for devices in energy-related applications using various chemical and physical routes. In this review article, we survey the most recent research works on the synthesis of heteroatom-doped graphene materials such as reduced graphene oxide, graphene oxide, graphene quantum dots and graphene nanoribbons. Applications of these materials in energy storage/conversion devices (supercapacitors, batteries, fuel cells, water splitting and solar cells) are also reviewed. Finally, the challenges and future perspectives for heteroatom-doped graphene materials are briefly discussed. We hope this article offers a useful starting point for researchers entering the field, providing an overview of synthesis approaches and energy applications.