Understanding the Oxygen Reduction Reaction Activity of Quasi-1D and 2D N-Doped Heat-Treated Graphene Oxide Catalysts with Inherent Metal Impurities

Abstract

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.

Ag-MnxOy on Graphene Oxide Derivatives as Oxygen Reduction Reaction Catalyst in Alkaline Direct Ethanol Fuel Cells

“…To determine the morphology and specific surface area of the electrocatalysts, SEM and gas adsorption experiments were performed. Figure 2 shows the sheet-like structure which can be assigned to the graphene derivative support materials also found in the literature [29,31,38]. The morphological difference between rGO and NGO is clearly indicated.…”

“…It can only be confirmed using the data from the elemental analysis that Ag is present in the correct proportion. However, if it is considered that the diffractograms are very similar to the It has been shown previously that the morphology of graphene-based metal support and the metal itself have a great impact on the activity of the electrocatalyst [18,19,29,32]. To determine the morphology and specific surface area of the electrocatalysts, SEM and gas adsorption experiments were performed.…”

“…A defect of this kind can be present as nitrogen functionalities, i.e., pyridinic-N, pyrrolic-N, and graphitic-N. There are several reports that show that N-functionalities have an active role in electrocatalysis [29][30][31][32]. Such an effect could be beneficial for the ORR in direct alkaline ethanol fuel cells [8].…”

“…Defects of this kind can be present as nitrogen functionalities, i.e., pyridinic-N, pyrrolic-N, and graphitic-N. There are several reports that show that N-functionalities have an active role in electrocatalysis and could be beneficial for ORR [8,[29][30][31][32]. Liu et al [33] described that supporting CoMn 2 O 4 with nitrogen-doped graphene enhanced the electrochemical activity of the catalyst, which was attributed to the availability of more active sites, higher conductivity, and synergistic effects caused by the nitrogen atoms.…”

A Novel Reduced Graphene Oxide Modified Carbon Paste Electrode for Potentiometric Determination of Trihexyphenidyl Hydrochloride in Pharmaceutical and Biological Matrices

“…Interestingly, we identified residual nitrogen (8 wt%) that could be incorporated during the reduction with hydrazine and residual Mn impurities (<1 wt%) introduced during the oxidation step with KMnO 4 . Both elements were reported to be beneficial for enhanced sensing applications as discussed in previous reports [55][56][57]. Additionally, Raman (Figure S3), TGA (Figure S4), FTIR (Figure S5), and XPS (Figure S6 and Table S2) experiments were performed to further characterize the prepared materials.…”