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

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 degrees 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.