Microwave hydrothermal synthesis of α-MnMoO₄ nanorods for high electrochemical performance supercapacitors

Pristine α-MnMoO₄ nanorods were facilely prepared via co-precipitation (Cp) and microwave hydrothermal (MH) methods. X-ray diffraction (XRD) patterns showed pure monoclinic crystalline phase α-MnMoO₄ for the heat treated powder at 500 °C. Fourier Transform Infrared (FTIR) spectra showed that the chemical bond structure of α-MnMoO₄ corresponds to the strong vibrational modes of Mo-O-Mo, Mo-O and Mo[double bond, length as m-dash]O. Raman spectra showed the structural bonding and crystalline nature of α-MnMoO₄. Field Emission Scanning Electron Microscope (FE-SEM) images exposed the nanorod shape of the α-MnMoO₄ powder, with diameters of ∼200 nm and lengths of ∼1.6 μm. Electrochemical studies of the Cp- and MH-MnMoO₄ nanorods with 2 M NaOH as the electrolyte showed specific capacitances of 143 F g^-1 and 551 F g^-1, respectively, at a 1 A g^-1 constant discharge current density. Cyclic voltammetric (CV) studies of the MH-MnMoO₄ nanorods at various scan rates revealed the presence of redox pairs, suggesting a pseudocapacitive nature. The structural stability at different current densities demonstrated the high rate performances and good reversible capacity retention of the calcined MH-MnMoO₄ nanorods. A cycling life stability study of MH-MnMoO₄ demonstrated a good capacity retention of 89% of the initial specific capacitance at 5 A g^-1 after 1000 cycles.