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

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.