Electrochemical performance of nano CuCo<inf>2</inf>O<inf>4</inf> and MnS solid solution

Abstract

Nano copper cobaltite/manganese sulfide, (1−x)CuCo2O4/xMnS (x = 0.0, 0.25, 0.5, 1) samples were synthesized applying thermolysis and hydrothermal process. Phase identification using x-ray diffraction and Rietveld analysis disclosed single-phase CuCo2O4 (CCO) for intermediate samples (x = 0.25, 0.5) implying that MnS phase is not formed. X-ray photoelectron spectroscopy (XPS) analysis proved incorporation of Mn and S into the CCO lattice forming a solid solution. The transmission electron microscope revealed homogenous nanoparticle morphology with a small range size distribution. XPS measurements unveiled the cation oxidation states of the constituent elements Co2+/Co3+, Cu2+/Cu+ and Mn2+/Mn3+ providing abundant redox electron pairs. The specific capacitance (Cs) obtained from cyclic voltammetry (CV) and galvanostatic charge/discharge (GSCD) curves is noticeably increased after the addition of MnS. The best electrochemical performance was obtained by the solid solution 0.75CuCo2O4/0.25MnS with a specific capacitance of 674 Fg−1 and high cycling stability. The electrochemical impedance spectroscopy (EIS), the Nyquist curves and the equivalent circuit for the 0.75CuCo2O4/0.25MnS solid solution electrode were discussed. [Figure not available: see fulltext.].