Ammonolysis synthesis of nickel molybdenum nitride nanostructures for high-performance asymmetric supercapacitors

Abstract

Binary metal nitride nanorods of nickel-molybdenum nitride (Ni₂Mo₃N) are synthesized by a one-pot hydrothermal method followed by calcination at 400 °C and ammonolysis at 800 °C. The material is characterized by electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Ni₂Mo₃N nanorods are tested as an electrode material for supercapacitors and 264 C g⁻¹ specific capacity is exhibited at 0.5 A g⁻¹ current density with a specific capacity of 108 C g⁻¹ at high current density (5 A g⁻¹), revealing 41% rate capability. The Ni₂Mo₃N electrode retained 81.4% of the specific capacity after 1000 cycles at 5 A g⁻¹ current density in the three-electrode system. A full cell device is constructed with Ni₂Mo₃N nanorods as the cathode, activated carbon (AC) as the anode, and porous cellulose paper as the separator in 6 M KOH electrolyte, and the Ni₂Mo₃N//AC asymmetric cell is assembled and exhibited a high specific capacity of 157 C g⁻¹ at 1 A g⁻¹ current density. Moreover, the asymmetric cell displayed an excellent cycling stability of 95.7% at a high current density (5 A g⁻¹) after 3000 cycles and showed a maximum energy density of 34.89 W h kg⁻¹ at 800 W kg⁻¹ power density. The overall electrochemical performance of Ni₂Mo₃N nanorods in a supercapacitor is remarkable, suggesting an ideal candidate for future electrochemical devices.