Incorporating Manganese Dioxide in Carbon Nanotube-Chitosan as a Pseudocapacitive Composite Electrode for High-Performance Desalination
Journal
ACS Sustainable Chemistry and Engineering
Journal Volume
6
Journal Issue
3
Pages
3196-3205
Date Issued
2018
Author(s)
Abstract
Pseudocapacitive electrode materials that involve a Faradaic process are being used in capacitive deionization (CDI). In the present work, manganese dioxide was electrodeposited onto a carbon nanotube-chitosan composite to create a pseudocapacitive electrode (denoted MnO2/CNT–CS) for an enhanced desalination performance. The benefits of coupling MnO2 with the CNT–CS matrix are attributed to the mesoporosity to facilitate ion transport, hydrophilicity to increase the electrochemical contact, and good electrical conductivity to improve the Faradaic charge-transfer of MnO2. The electrochemical properties were investigated by electrochemical impedance, galvanostatic charge–discharge and cyclic voltammetry studies. Considering its low specific surface area (89.8 m2 g–1), the MnO2/CNT–CS composite electrode exhibited pseudocapacitive-like behaviors with a high specific capacitance (42.3 F g–1 at 5 mV s–1) and good rate capability. Furthermore, when the MnO2/CNT–CS electrode served as a cathode in batch-mode CDI at 1.2 V, the salt adsorption capacity was 6.01 mg g–1 for 1 mM NaCl, which is higher than that of most MnO2-coated carbon electrodes. The improved sorption capacity was ascribed to the intercalation of Na+ ions via the Mn redox reaction between +4 and +3 oxidation states. The cycling performance was further tested over 15 charge–discharge cycles. Consequently, the pseudocapacitive MnO2/CNT–CS electrode is a promising cathode material for high-performance desalination. These results also suggest a promising approach for using redox-active MnO2 in CDI.
Type
journal article