Review: Two-dimensional nanostructured pristine graphene and heteroatom-doped graphene-based materials for energy conversion and storage devices

With the goal of achieving net zero carbon emissions and the growing scarcity of fossil fuels, significant efforts have been devoted to the development of high-efficiency, low-cost, environmentally friendly, and alternative energy conversion and storage devices. Pristine graphene, consisting of single-atom-thick carbon nanosheets arranged in an sp² hybridized honeycomb lattice, has emerged as a primary building-block material, including a large surface area, mechanical strength, chemical inertness, and superior electric and thermal properties. Since pristine graphene has a band gap of zero, which significantly limits its applications, modifying graphene by incorporating a heteroatom is a highly effective method to enhance its properties. This approach enhances the suitability and potential of heteroatom-doped graphene as an electrode material in energy conversion and storage devices. This review comprehensively describes the current synthesis advancements in pristine graphene, and heteroatom-doped graphene-based electrocatalysts and/or electrode materials for two types of energy conversion: fuel cells, and water splitting, as well as three frontier energy storage devices, namely supercapacitors and lithium-based various types of batteries. To this end, an exploration of the future prospects, opportunities, and challenges pertaining to the application of graphene and its heteroatom-doped graphene in energy conversion and storage devices is anticipated. This comprehensive review article aims to pave the way for novel advancements and practical utilization of heteroatom-doped graphene-based materials in various domains.