Needle-like MnO2/activated carbon nanocomposites derived from human hair as versatile electrode materials for supercapacitors

Bio-waste material, human hair, was used as a source to prepare activated carbon (ACs) by a simple NaOH activation method. MnO2 with a needle like structure was successfully decorated on ACs by a wet impregnation method. TEM images confirmed the needle-like morphology of MnO2 on ACs. The chemical state of Mn in MnO2/ACs was found to be +4, as confirmed by XPS analysis. Other physicochemical properties of MnO2/ACs were investigated by means of SEM-EDS, XRD, Raman and XPS analyses. After complete characterization, the resultant nanocomposites with different MnO2-loading [MnO2/ACs((X : Y))] were employed as electrode materials for supercapacitors. Interestingly, the MnO2/ACs nanocomposites showed an excellent capacitance in three different electrolytes (1.0 M H2SO4, 1.0 M KOH and 1.0 M Na2SO4). The MnO2/ACs(1 : 12) achieved a maximum capacitance of 410 F g(-1), 345 F g(-1) and 291 F g(-1) in 1.0 M H2SO4, 1.0 KOH and 1.0 Na2SO4, respectively. To the best of our knowledge, this is the first MnO2-based carbon nanocomposite to show good capacitance performance in three different kinds of electrolytes. Moreover, the MnO2/ACs showed a capacitance of similar to 300 F g(-1) even after 500 cycles in 1.0 M H2SO4.