The effect of phosphorus and nitrogen dopants on structural, microstructural, and electrochemical characteristics of 3D reduced graphene oxide as an efficient supercapacitor electrode material

Abstract

Supercapacitors are environmentally friendly and safe energy storage devices for diverse applications. The electrode material's structural, microstructural, and electrochemical properties are crucial determinants of supercapacitor capacity. One effective method to improve electrode performance is introducing doping heteroatoms or synthesizing composite materials. In this study, three-dimensional reduced graphene oxide (3D rGO) doped with Phosphorus, Nitrogen, or both (N/P co-doped) was synthesized for high-efficiency, supercapacitors using a facile, fast, and cost-effective hydrothermal process. The hydrothermal reduction of graphene oxide involved substituting Phosphorus and Nitrogen elements with carbon atoms. Moreover, the effect of dopants on structural and microstructural characteristics of 3D rGO was evaluated using different techniques, and the electrochemical characteristics were evaluated by cyclic voltammetric (CV) analysis, galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS). The specific capacitance of 3DN/PrGO on Ni foam reached 648 F g−1 at 1 Ag−1, in a voltage range of −0.6 –0.6 V (vs. Ag/AgCl), using 6 M KOH as the electrolyte. High energy density and power density of 6.1 wh/kg and 513 w/kg were obtained, respectively. The stability test was also conducted, and appropriate stability over 100 charging and discharging cycles was observed. The considerable performances are mainly due to the combined effect of pseudocapacitive properties of Nitrogen and Phosphorus dopants, improved wettability, and the porous structure of 3D rGO, which provides suitable electroactive sites and simplifies the electron/ion transfer for the electrochemical reactions.