Synthesis and Pseudocapacitive Behavior of Nickel Molybdate/Mutiwalled Carbon Nanotubes Composite

A novel nickel molybdate/mutiwalled carbon nanotubes (NiMoO4/MWCNTs) composite was synthesized by hydrothermal method using nickel nitrate, sodium molybdate and MWCNTs as raw materials, and the product was characterized by scanning electronic microscopy, energy dispersive spectra, and X-ray diffraction spectra. The scanning electron microscopy results showed that pseudo-spherical NiMoO4 was wrapped with MWCNTs and all elements were uniformly distributed in the material. Cyclic voltammetry and electrochemical impedance spectra revealed that the presence of MWCNTs greatly improved the redox signal and electron transfer kinetics of NiMoO4. The capacitance tests further indicated that the composite presented better specific capacitance, rate capability, and cycling stability than the single-component of NiMoO4, and with a MWCNTs content of 40 mg the composite (NiMoO4/MWCNTs-40) displayed the best electrochemical performance. At the current density of 2 A/g, the NiMoO4/MWCNTs-40 composite demonstrated a remarkable specific capacitance of 1071 F/g; while current density was increased to 10 A/g and the capacitance still remained 66.10%. Cyclic stability experiment revealed that the NiMoO4/MWCNTs-40 composite retained 95.85% of its initial specific capacitance after 2500 charge-discharge cycles at a current density of 10 A/g, exhibiting prominent electrochemical stability.