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.