Synthesis and Mechanism of Ultra-Stable Mn/S Co-Doped Nico2o4 Electrodes for Supercapacitors

Abstract

By taking advantage of metallic Mn element with multivalent and active redox characteristics, and S with fascinating non-metallic properties, this work successfully synthesizes the new type of Mn/S co-doped NiCo2O4 electrode on the pre-treated Ni foam via hydrothermal method. Intriguingly, applying pre-treatment to Ni foam creates the forest-like nanoarrays on its surface, which helps to anchor the Mn/S co-doped NiCo2O4 materials (active substances) and establish a more stable connection between Ni foam and the active substances. Moreover, the Mn/S co-doped nanosheets on the pre-treated Ni foam become curly and much thinner compared with the non-doping material, providing abundant active sites. Notably, the Mn/S co-doped NiCo2O4 electrode demonstrates a remarkable specific capacitance of 5.31 F cm-2 (over three times that of the non-doped one), and an outstanding cycle stability (93.46% retention after 12000 cycles), which is ascribed to the synergistic effect of Mn and S elements and the stable integrated structure caused by the pre-treatment of Ni foam. DFT calculations are further conducted to elucidate the influence of Mn/S co-doping on the electronic structure of the electrode and the adsorption capacity for OH− ions, which deepens the comprehension of the high electrochemical performance.

Keywords: Co-doping, First principles, Pre-treatment, Supercapacitor