Electrodeposited Manganese Dioxide/Activated Carbon Composite As a High-Performance Electrode Material for Capacitive Deionization

Electrode materials are a crucial component for achieving high desalination performance via capacitive deionization (CDI). In the present work, we have successfully fabricated a manganese dioxide (MnO2)/activated carbon (AC) composite electrode using an anodic electrodeposition technique. Surface characterization confirms the presence of electrodeposited MnO2 on the AC surface with an amorphous structure and improved wetting behavior. Cyclic voltammetry and galvanostatic charge/discharge measurements indicate that the MnO2/AC composite electrode exhibits a high specific capacitance (77.6 F g–1 at 5 mV s–1), rate capability, and excellent cycling reversibility for capacitive charge storage. Furthermore, the salt electrosorption capacity is investigated using batch mode experiments at a working voltage of 1.0 V in a 0.01 M NaCl solution. The MnO2/AC composite electrode presents a superior electrosorption capacity of 9.3 mg g–1, which is approximately 1.6-fold higher than that of the pure AC electrode (5.7 mg g–1). This significant improvement can be attributed to the mixed capacitive-Faradaic process, corresponding to the combination of the double-layer charging of the high specific surface area (625 m2 g–1) and the pseudocapacitive redox reaction of MnO2. Therefore, the electrodeposited MnO2/AC composite is a potential electrode material for high-performance CDI.