Solid-phase synthesis and electrochemical pseudo-capacitance of nitrogen-atom interstitial compound Co3N

Abstract

Metal nitrides have great potential for electrochemical energy storage, but are relatively scarcely investigated. Herein, a novel metal nitride, Co₃N, is prepared by nitridation using a Co₃O₄ precursor heated at 500 °C for 2 h in flowing NH₃, and characterized by using X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and energy dispersive spectroscopy (EDS) methods. Besides, the electrochemical properties of Co₃N are investigated using cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS). The as-prepared Co₃N demonstrates remarkable electrochemical performance with a high specific capacitance of 112.3 F g⁻¹ at a current density of 0.5 A g⁻¹, good rate capability (72.4%, from 0.5 to 5 A g⁻¹) and superior cycling stability (109.7% retention over 10 000 cycles at a current density of 2 A g⁻¹). Finally, a Co₃N//activated carbon (AC) asymmetric supercapacitor (ASC) is successfully assembled by using Co₃N and AC as the positive electrode and negative electrode, respectively. The as-fabricated ASC device can achieve a maximum energy density of 12.1 W h kg⁻¹ at a power density of 204.6 W kg⁻¹, which shows that the Co₃N material should be a potential electrode material for supercapacitors.