rGO-SnO2；Efficient electrode material for capacitive deionization application   Syed Kamran Sami1, 2, Jung-Yong Seo1,Tae-Il Kim1, and Chan-Hwa Chung1* 1School of Chemical Engineering, Sungkyunkwan University (SKKU), Suwon, 16419, Republic of Korea 2 Balochistan University of Information technology, Engineering & Management Sciences (BUITEMS),Quetta, 87300, Pakistan *E-mail: chchung@skku.edu Abstract Introduction (http://www.titanium.org) Fresh water is quickly becoming a limited resource with a rising global demand. The solution to the fresh water scarcity is desalination of sea water. Massive energy consumption and high costs are an obstacle for the practical application of desalination technology. Here, we report the development of an efficient electrode material for capacitive deionization system to overcome the problem of desalination. rGO-SnO2 nano-composite were synthesized by ecofriendly and facile hydrothermal process. The synthesized composite showed better electrochemical performance and possess excellent capacitance retention of 60 % at higher scan rates. In a specialized design CDI cell the synthesized nano-composite showed excellent cyclic performance, high reversibility and remarkable electro-sorption capacity of 17.66 mg/g at 1.2 V applied potential with initial salt concentration of 400 mg/L. Moreover, it was found that the system has a rapid ion removal rate and excellent stability in an aqueous sodium chloride solution. These results suggested that this system could be a feasible method for desalination in capacitive techniques. Capacitive deionization (CDI) is a promising new technology for water desalination making use of an electrical voltage applied between two porous carbon electrodes. Even at low voltage value of 1.2 V, desalinated water can be produced. (Energy Environ. Sci., 2015, 8, 2296-2319) Methodology Graphene Oxide Graphene Oxide + SnCL2 + NaBH44 rGO-SnO2 Hydrothermal Ion Intercalation 120oC (12hrs) SnO2 rGO Electrode Fabrication rGO-SnO2(80 wt.%) Carbon black (10 wt.%) PVDF (10 wt.%) Grinding with mortar, then coated on Carbon felt SnCl2 Sn source Graphene Oxide rGO precursor NaBH4 Reducing agent Hydrothermal synthesis at 120 oC for 12 hours. Washing with DI water and overnight drying at 60 oC . Nanocomposite Synthesis Characterization Electrochemical Performance CDI Performance Schematic Illustration of Process flow TEM image of synthesized nanocomposite. Characterization Electrochemical Performance -Measurement Conditions- 0 V – 0.8 V 5mV - 200 mV Scan rate Specific Capacitance Calculation   Working Electrode ( rGo-SnO2) Counter Electrode ( Pt Foil) Reference Electrode ( Ag/AgCl) Electrolyte (0.5M NaCl ) Electrosorption Capacity Calculation  Co = Initial concentration  (mg/L) C = Final concentration  (mg/L)  V (L) = total volume of the NaCl solutions m (g) = mass of the active material XRD , XPS , FTIR , Raman spectroscopy and BET surface are of rGO-SnO2 Capacitive deionization Performance Summary rGO-SnO2 nanocomposite has been synthesized by eco-friendly and facile hydrothermal synthesis with good morphology . Doping of SnO2 nanoparticles on rGO sheets increases the surface area which enhanced the electrochemical behavior. Synthesized nanocomposite electrode showed good capacitance retention at scan rates. (5 to 100 mV/s)Capacitance retention of the nanocomposite electrode is 65 %. Desalination performance of nanocomposite electrode was tested at 0.8, 1.0， and 1.2 V constant potential。 It was found that at 1.2 V applied potential with initial conductivity 566 µS/cm. rGO-SnO2 composite electrode demonstrated remarkable elecrosorption capacity (17.66 mg/g) as compared to rGO (6.3 mg/g). rGO-SnO2 composite electrode demonstrated excellent reversibility and stability. Synthesized nanocomposite is considered to be suitable and desirable material for desalination application with good electrochemical performance and desalination capacity. Schematic diagram of experimental module Capacitive deionization performance