Carbon-based nanomaterials (fullerenes, carbon nanotubes, graphene derivatives, etc.) are promising cost-effective catalyst alternatives to noble metal catalysts for the oxygen reduction reaction (ORR). Herein, we report on the synthesis and characterization of graphene-based derivatives with various aspect ratios. All the synthesized materials were critically probed for activity and stability for ORR in acidic and alkaline electrolytes. Namely, a comparison study on the influence of aspect ratio and N-doping on ORR electroactivity in acidic and alkaline electrolytes of quasi-1D N-doped heat-treated graphene oxide nanoribbons (N-htGONr) with 2D N-doped heat-treated graphene oxides (N-htGO) was done. Moreover, we also investigated the influence of metallic impurities on the ORR activity in acidic and alkaline media. We have shown that a higher aspect ratio plays an important role in improving ORR activity. Furthermore, when comparing N-doped derivatives with non-doped derivatives, the ORR activity in 0.1 M HClO4 is increased by N-doping; however, in 0.1 M KOH, the N-doping effect is overshadowed by inherent transition metal impurities, i.e., iron. In this respect, we have established a linear correlation between onset potential for ORR, iron concentration, and BET specific surface area of graphene-based derivatives. The present study will aid in the critical assessment and development of non-metallic catalysts for the electrochemical energy conversion devices.

The development of an environmentally friendly, safe and efficient method to produce hydrogen peroxide (H2O2) by electrocatalysis is an attractive alternative to the current anthraquinone autoxidation process. In this study,...

Graphene derivatives doped with nitrogen have already been identified as active non-noble metal materials for oxygen reduction reaction (ORR) in PEM and alkaline fuel cells. However, an efficient and scalable method to prepare active, stable, and high-surface-area non-noble metal catalysts remains a challenge. Therefore, an efficient, potentially scalable strategy to improve the specific surface area of N-doped graphene derivatives needs to be developed. Here, we report a novel, rapid, and scalable electrical induction heating method for the preparation of N-doped heat-treated graphene oxide derivatives (N-htGOD) with a high specific surface area. The application of the induction heating method has been shown to shorten the reaction time and improve the energy efficiency of the process. The materials synthesized by induction heating exhibited very high specific surface area and showed improved ORR activity compared to the conventional synthesis method. Moreover, we demonstrated that the temperature program of induction heating could fine-tune the concentration of nitrogen functionalities. In particular, the graphitic-N configuration increases with increasing final temperature, in parallel with the increasing ORR activity. The presented results will contribute to the understanding and development of nonmetal N-htGOD for energy storage and conversion applications.

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.