The effect of nitrogen-based additives on the synthesis of modified graphene materials and their performance in supercapacitor applications

Electrochemical exfoliation offers a scalable and green route to synthesize graphene with tunable structural and electrochemical properties. In this work, nitrogen-containing additives: Ethylenediaminetetraacetic acid tetrasodium salt dihydrate (EDTA), Ethylenediamine-N,N’-diacetic acid (EDDA), Nitrilotriacetic acid trisodium salt (NTA), Sodium iminodiacetate dibasic hydrate (IAA), and Ethylenediamine-N,N’-disuccinic acid trisodium salt (EDDS), with varying properties were used to study their role in functionalization and porosity development during aqueous exfoliation of graphite. N-based additives achieve this by altering the bandgap, surface energy, and charge distribution. The materials were characterized using UV-Visible, FTIR, XRD, and Raman spectroscopy. UV-Vis, XRD, and Raman confirmed the formation of multilayer graphene (MLG). The prominent D band in Raman and SEM images of MG-IAA and MG-EDDS confirmed functionalization and porosity. FTIR data suggest that nitrogen and oxygen containing functionalities may present in the MG materials. Electrochemical characterization via CV, GCD, and EIS in a three-electrode setup revealed significant improvements over graphite (12.07 F g⁻¹) and graphene (18.59 F g⁻¹). MG-EDTA, MG-EDDA, MG-NTA, MG-IAA, and MG-EDDS showed specific capacitances of 35.71, 38.24, 48.75, 29.56, and 25.30 F g⁻¹ respectively at 5 mV s−1. MG-NTA showed a 304% enhancement compared to graphite. A power-law analysis revealed b-values from 0.15 (graphite) to 0.66 (MG-EDDA), indicating a shift from diffusion-limited to surface-controlled processes. MG-NTA delivered the highest energy and power densities (20.49 Wh kg⁻¹, 449.94 W kg⁻¹), followed by MG-IAA (13.00 Wh kg⁻¹, 450.00 W kg⁻¹), MG-EDDA (4.51 Wh kg⁻¹, 249.78 W kg⁻¹), MG-EDTA (5.83 Wh kg⁻¹, 299.83 W kg⁻¹), and MG-EDDS (4.15 Wh kg⁻¹, 324.95 W kg⁻¹). Donor strength, net charge, electrochemical reactivity, and geometry of the N-based additives influenced the pore formation and/or functionalization. NTA proved to be a promising additive due to its moderate donor strength, charge, electrochemical reactivity, and favorable geometry compared to the other additives. This mechanistic study provides insight into tuning pore formation and/or functionalization of graphene for high-performance supercapacitor applications.