Electrochemical behavior of spray deposited mixed nickel manganese oxide thin films for supercapacitor applications

The relatively low energy density is a crucial issue obstructing the growth of supercapacitors as energy storage devices. Various tactics have been developed to enhance the energy density. Nickel manganese oxide thin films have been synthesized by spray pyrolysis on preheated amorphous and FTO coated glass substrates. These films are characterized for structural, morphological and optical properties using X-ray diffraction, scanning electron microscopy and UV–Vis spectrophotometer. XRD study illustrates formation of spinel cubic NiMn₂O₄ as prominent phase with crystalline size 11 nm. SEM shows fractured surface morphology; wherein small pores on the surface are covered by the particles. Optical band gap of 1.98 eV is observed. The electrochemical performance of NiMn₂O₄ electrode is studied by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy measurements. The maximum specific capacitance is found to be 460 Fg⁻¹ at scan rate of 5 mVs⁻¹. The excellent rate capability and long term stability suggests NiMn₂O₄ thin film to be good candidate for electrochemical supercapacitors.