Cathodic electrosynthesis of ZnMn₂O₄/Mn₃O₄ composite nanostructures for high performance supercapacitor applications

ZnMn₂O₄/Mn₃O₄ composite nanostructures were prepared by cathodic electrodeposition followed by heat treatment. A mixed hydroxide precursor was galvanostatically electrodeposited from aqueous solution containing Mn and Zn (as nitrates) and the obtained precursor was annealed to prepare the composite. This composite exhibited much better electrochemical behaviors than bare Mn₃O₄. Rietveld analysis of the X-ray diffraction (XRD) data showed that the product was composed of Mn₃O₄, ZnMn₂O₄ and minor amounts of λ-MnO₂. Furthermore, the obtained composite was characterized by Fourier transform infrared spectrometry (FT-IR) and energy dispersive spectrometry (EDS). Field emission scanning electron micrographs (FE-SEM) and transmission electron micrographs (TEM) revealed co-existence of nanoparticles and high aspect ratio nanorods. Electrochemical performance and ion transport of ZnMn₂O₄/Mn₃O₄ composite were studied via galvanostatic charge-discharge (GCD) cycling and electrochemical impedance spectroscopy (EIS). Cyclic voltammetric (CV) measurements showed a maximum specific capacitance of 321.34 F/g at the scan rate of 1 mV/s. 93% of this specific capacitance was retained after 2000 cycles. - Highlights: • ZnMn₂O₄/Mn₃O₄ composite was synthesized by cathodic electrodeposition. • The prepared composite possess nanosized rod/particle morphology. • The prepared composite nanostructure exhibited a maximum storage capacity of 321.34 Fg⁻¹.