Evaluation of electrochemical hydrogen storage capability of three-dimensional nano-structured nitrogen-doped graphene

Abstract

In this work, nitrogen-doped graphene foam was synthesized by using hydrothermal routes. In the first step, graphene was synthesized by utilizing a modified Hummer's method and nitrogen-doped graphene foam was then synthesized at 180 °C by using an ammonia and graphene solution for 12 h. X-ray photon spectroscopy (XPS) was applied to determine the extent of doping by nitrogen on the graphene foam; three N-peaks were observed at 398.25, 399.69, and 401.46 eV, and XPS also showed that 6 at% of the synthesized graphene foam consisted of nitrogen atoms. The capability of this foam to absorb hydrogen was evaluated in a 6 M KOH solution through electrochemical impedance spectroscopy (EIS), galvanostatic charge/discharge, and cyclic voltammetry (CV) analysis. The hydrogen storage capacity of the achieved N-doped GF, showing the value of 1916.5 mAh.g−1 significantly improved in comparison to that of pure graphene in previous work, due to the increasing electronegative sites at the surface of the graphene foam.