From environmental pollutant to activated carbons for high-performance supercapacitors

In this research, Methylene blue (MB), a type of environmental pollutants (dye), was initially adopted as a carbonaceous precursor to synthesize activated carbons (ACs) with the activation of ZnCl2 at high temperatures. Varieties of techniques have been used to characterize the MB-derived ACs. The pore structures and surface functional groups were fully studied by N2 adsorption-desorption analysis, XPS, IR, SEM and TEM, respectively. The MB-derived ACs have as large specific surface area as up to 2151.92 m2g−1 and the pore size distribution concentrates on 2-5 nm. Moreover, electrochemical techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge (GCD) were employed to assess AC's capacitive behavior and rate performance. It demonstrated that MB-derived ACs possessed as high specific capacitance as 265 Fg−1 at a scan rate of 5 mV s−1 in 1 M H2SO4. In addition, the MB-derived ACs exhibited long-term cycling stability and more than 90% original capacity have been maintained after first 1000 cycles (the total cycles of 10000 were carried out.) at a high current density of 1 A g−1.