Construction of an inverted-capacitive deionization system utilizing pseudocapacitive materials

An inverted-capacitive deionization (i-CDI) cell of MnO2//polypyrrole-coated activated carbon (MnO2//PPy@AC) with pseudocapacitive characteristics enables unique salt-removal/salt-concentration capability. The salt adsorption capacity (SAC) of MnO2//PPy@AC highly depends on the discharging time and a high SAC of 27.6 mg.g(-1) is obtained at the 60-min discharging time. The SAC retention of this unique cell is 100% after 10 charge/discharge cycles at 1.2/0 V. The memory effect of MnO2//PPy@AC is confirmed by the unchanged conductivity of the cell when the applied cell voltage is interrupted, which has been demonstrated for salt-removal and salt-concentration applications.