Nowadays, population growth have compelled us to produce more clean water to secure safe water supplies. Capacitive deionization (CDI) is an electric-field assisted desalination process, which has been considered as one of the most emerging technologies for removing salt ions or ionic contaminants from aqueous solutions. Most recently, pseudocapacitor has been revealed to greatly improve electrosorption capacity of the electrode by fast and reversible Faradaic reactions. Manganese dioxide (MnO2) as a transition metal oxide is a promising electrochemical active material due to its low cost, high theoretical capacitance value, easy and controlled synthesis, and environmental friendliness. However, the application of MnO2 electrode is limited because of its poor electrical conductivity. Hence, it is important to develop a composite electrode with conducted carbon-based materials, which can overcome the disadvantage of MnO2. In this study, composite electrodes of MnO2 on three carbonaceous materials namely activated carbon (AC), multi-wall carbon nanotube (MWCNT), and multi-wall carbon nanotube base on sponge (SMWCNT). To make sure the successfully electrodeposition of MnO2, the morphology and structure of composite electrodes were characterized using nitrogen adsorption/desorption isotherm, scanning electron microscopy, X-ray photoelectron spectrum, X-ray diffraction. In addition, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy were used to characterize the electrochemical properties of these composite electrodes. Lastly, salt adsorption capacities of composite electrodes were determined by batch-mode CDI experiments at an applied voltage of 1.0 V for desalting 2 mM NaCl solution. As a result, the electrosorption capacity of MnO2-AC electrode was significantly improved to 4.4 mg/g as compared to that of AC electrode (3.7 mg/g). MnO2-MWCNT had a higher electrosorption capacity of 7.1 mg/g than MnO2-AC electrode. We except the MnO2-SMWCNT electrode will have highest electrosorption capacity among these three electrodes because of its great conductivity of carbon nanotube and 3-D structure of sponge. In particular, 3-D structure can provide numerous macro-channels for the rapid transport pathway of ions from multiple directions into the pore network. Consequently, as evidenced by the experimental results, using MnO2 with carbon based as electrode materials has a great potential for capacitive desalination.

Enhanced desalination performance of carbon-based electrodes via pseudocapacitance using manganese dioxide in capacitive deionization

254th National Meeting (2017)

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