Chemical synthesis of Co and Mn co-doped NiO nanocrystalline materials as high-performance electrode materials for potential application in supercapacitors

Abstract Co and Mn co-doped with NiO nanostructued materials, such as, Ni0.95Co0.01Mn0.04O1−δ, Ni0.95Co0.04Mn0.01O1−δ and Ni0.95Co0.025Mn0.025O1−δ were synthesized by chemical synthesis route and studied for potential application as electrode materials for supercapacitors. The phase structure of the materials was characterized by X-ray diffraction (XRD) and the crystallographic parameters were found out and reported. FTIR (Fourier Transform Infrared) spectroscopy revealed the presence of M–O bond in the compounds. The particle size of the materials was found to be in the range of 291.5–336.5 nm. The morphological phenomenon of the materials was studied by scanning electron microscopy (SEM) and the particles were found to be in spherical shape with average grain size of 14–28 nm. EDAX analysis confirmed the presence of appropriate levels of elements in the samples. The in-depth morphological characteristics were also studied by HR-TEM (High Resolution Tunneling Electron Microscopy). Cyclic voltammetry, chronopotentiometry and electrochemical impedance measurements were applied in an aqueous electrolyte (6 mol L−1 KOH) to investigate the electrochemical performance of the Co and Mn co-doped NiO nanostructured electrode materials. The results indicate that the doping level of Co and Mn in NiO had a significant role in revealing the capacitive behaviors of the materials. Among the three electrode materials studied, Ni0.95Co0.025Mn0.025O1−δ electrode material shows a maximum specific capacitance of 673.33 F g−1 at a current density of 0.5 A g−1. The electrochemical characteristics of blank graphite sheet were studied and compared with the performance of Co/Mn co-doped NiO based electrode materials. Also, Ni0.95Co0.025Mn0.025O1−δ has resulted in a degradation level of 4.76% only after 1000 continuous cycles, which shows its excellent electrochemical performance, indicating a kind of potential candidate for supercapacitors.