Heteroatom-doped graphene: From fabrication to supercapacitor and batteries energy storage applications

Graphene, despite its exceptional properties, requires certain surface and structural modifications to enhance its performance in energy storage applications. The introduction of dopants can create charge carriers that can improve electrical conductivity and the overall properties of graphene. However, careful control over dopant concentration is crucial since excessive doping can lead to the formation of defects that can hinder electron mobility. This review discussed the functionalization of graphene, dopant selection criteria, heteroatom-doped graphene preparation techniques, and the energy storage applications of the doped graphene system. Dopant selection is very important as it determines the applications of the doped graphene. Various synthesis methods, including chemical vapor deposition (CVD), solvothermal, hydrothermal, ball milling, electrochemical synthesis, thermal annealing, plasma synthesis, and arc discharge, have been explored for the fabrication of heteroatom-doped graphene. Each technique presents its distinct advantages and challenges, thereby influencing the materials scalability, cost, and properties. For instance, solvothermal and hydrothermal methods can produce scalable and cost-effective materials, while ball-milling and the electrochemical synthesis routes offer simplicity and low operational costs. The CVD technique, while advantageous, faces challenges in large-scale production, due to some complex mechanisms. Plasma synthesis provides tunability and environmental benefits but suffers from high-temperature issues. The thermal annealing and the arc discharge methods offer efficient production, but they require thorough optimization of temperature and current, respectively. Therefore, this review provides concise evidence and a thorough examination of the production of heteroatom-doped graphene for supercapacitor and lithium-ion batteries energy storage applications. Hydrothermal and solvothermal synthesis methods have shown high possibilities in the production of sustainable heteroatom-doped graphene for energy storage applications. The review further confirms the possibility for the use of heteroatom-doped graphene, with its fast electrolyte ion diffusion, compact porosity, high capacitance, and long cycle life, in the production of commercial supercapacitor, lithium-ion and sodium-ion batteries electrodes.