Highly Exfoliated N-Doped Reduced Graphene Oxide Derivatives Synthesis and Application

Carbon-based nanomaterials such as graphene, graphene oxide, carbon nanotubes, graphene nanoribbons, etc. are considered as promising materials for energy storage and conversion, electrode sensing, optical and electronic applications. High specific surface area, porosity, and chemical modifications are some of the most important factors for tailoring the (electro)chemical, physical, and mechanical properties of graphene derivatives.1 Nitrogen-doped graphene derivatives have been identified as promising materials for energy storage and conversion2 and sensing applications. One of the most common syntheses of N-doped graphene derivatives is the N-doping of graphene oxide prepared by the Hummers method. The methods for simultaneous N-doping and reduction of graphene oxide are diverse: thermal annealing, pyrolysis, solvothermal, laser ablation, microwave-assisted, and hydrazine treatment.1 However, the above methods yield N-doped graphene derivatives, which are usually poorly exfoliated and have a low specific surface area. Therefore, an efficient strategy to improve the specific surface area of N-doped graphene oxide derivatives needs to be developed.3 Herein we present a new "induction heating method" for the preparation of N-doped reduced graphene oxide derivatives (N-rGOD) with a high specific surface area. N-rGOD was prepared in a two-step process from commercially available graphites (Gs) and multi-walled carbon nanotubes (MWCNTs). In the first step, graphite oxide precursors were synthesized from Gs or MWCNTs by the improved Hummers method. In the second step, the graphite oxide precursors were subjected to rapid heat treatment by induction heating in a reductive ammonia atmosphere. Due to the rapid thermal expansion of graphite oxide, massive exfoliation occurred to obtain N-rGOD with higher specific surface area.4 These materials were tested for energy storage and conversion applications and showed excellent properties. References (1) Xu, H.; Ma, L.; Jin, Z. Nitrogen-Doped Graphene: Synthesis, Characterizations and Energy Applications. J. Energy Chem. 2018, 27 (1), 146–160. https://doi.org/10.1016/j.jechem.2017.12.006. (2) Nosan, M.; Löffler, M.; Jerman, I.; Kolar, M.; Katsounaros, I.; Genorio, B. Understanding the Oxygen Reduction Reaction Activity of Quasi-1D and 2D N-Doped Heat-Treated Graphene Oxide Catalysts with Inherent Metal Impurities. ACS Appl. Energy Mater. 2021. https://doi.org/10.1021/acsaem.1c00026. (3) Alazmi, A.; El Tall, O.; Rasul, S.; Hedhili, M. N.; Patole, S. P.; Costa, P. M. F. J. A Process to Enhance the Specific Surface Area and Capacitance of Hydrothermally Reduced Graphene Oxide. Nanoscale 2016, 8 (41), 17782–17787. https://doi.org/10.1039/c6nr04426c. (4) Qiu, Y.; Guo, F.; Hurt, R.; Külaots, I. Explosive Thermal Reduction of Graphene Oxide-Based Materials: Mechanism and Safety Implications. Carbon N. Y. 2014, 72, 215–223. https://doi.org/10.1016/j.carbon.2014.02.005.