The role of carbon nanotubes on the capacitance of MnO2/CNTs

The electrochemical behavior of MnO2/carbon nanotubes (CNTs) has been studied by using cyclic voltammetry, galvanostatic charge discharge measurement and electrochemical impedance spectroscopy in 0.5 M Na2SO4 solution. The loading mass of CNTs, the potential sweep rate as well as the frequency have been investigated in detail to make clear of their influence on capacitance, resistance, and relaxation time constant. The dependence of the voltammetric surface charge q* on different loading mass of CNTs and potential scan rate has been investigated. With the addition of CNTs, resistance and relaxation time constant of the material are reduced and the rate capability increased. In particular, CNTs is beneficial for the outer surface capacitance contribution of MnO2. The outer surface capacitance contribution of MnO2/CNTs (1: 1) can reach 67% total capacitance contribution.