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Date of Award


Document Type

Campus Access Master's Thesis

Degree Name

Master of Science in Materials Science and Engineering (MS)

Administrative Home Department

Department of Materials Science and Engineering

Advisor 1

Yun Hang Hu

Committee Member 1

Joshua M. Pearce

Committee Member 2

Shiyue Fang


Capacitive deionization (CDI) is an emerging technology for water desalination via facile removal of charged ionic species from aqueous solutions. The mechanism of CDI is based on ion adsorption by forming electric double layers at the electrode/electrolyte interface or conducting the reversible faradaic reaction at/near the electrode surface. Thus, electrode materials can significantly affect the CDI performance. Cobalt sulfide with demonstrated supercapacitor performance shows great potential for CDI electrode. In this thesis, flower-like β-cobalt sulfide (CoS1.097) were successfully synthesized through hydrothermal reaction. It has been demonstrated that the morphology and structure of CoS1.097 are greatly influenced by hydrothermal temperature. The sample of CoS1.097 synthesized at 140oC for 8 h exhibited the best electrochemical performance with a maximum specific capacity of 121 F/g at the current density of 0.2 A/g in 1M NaCl aqueous solution. However, further improvement of electrosorption capacity was constricted by poor conductivity and low surface area of CoS1.097. Therefore, the combination of activated carbon (AC) and CoS1.097 seems to be a feasible strategy by utilizing the high electrochemical activity of CoS1.097 and the high conductivity and the large surface area of AC. Herein, AC/CoS1.097 composites were constructed by hydrothermal method and hot plate method, respectively. Hot plate AC/CoS1.097 possessed a specific capacity of 260 F/g at 0.2 A/g in 1M NaCl solution, which was higher than that of hydrothermal AC/CoS1.097 (197 F/g). It may be attributed to the excellent synergistic combination and the smaller size CoS1.097 particles of hot plate AC/CoS1.097. In addition, hot plate AC/CoS1.097 can reach a maximum electrosorption capacity of 3.1 mg/g at 1.2 V in 28 ml of 100 mg/l NaCl solution in flow-type CDI cell, which makes it a suitable electrode material for large-scale CDI application.