Ion Removal Performance and Enhanced Cyclic Stability of SnO2/CNT Composite Electrode in Hybrid Capacitive Deionization

Abstract Hybrid capacitive deionization (HCDI) is developed based on capacitive deionization (CDI) for water treatment, which combines CDI with a battery system. Developing the high-performing battery electrode materials is a significant point for HCDI. Herein, SnO2/CNT was fabricated according to hydrothermal method, which was denoted as SnO2/CNT-H, after calcination, the obtained product was denoted as SnO2/CNT-HC. The as-prepared SnO2/CNT-HC was used in HCDI system for the first time, which demonstrated a salt adsorption capacity of 9 mg g-1 and ultrafast salt adsorption rate of 2.5 mg g-1 min-1 at 500 mg L-1 initial NaCl concentration. The SnO2/CNT-HC electrode also had a good cyclic stability of keeping 120 % of salt adsorption capacity after 100 adsorption-desorption cycles at 1.0 V and 500 mg L-1 NaCl solution. Moreover, when this system was used to study the adsorption-desorption performance for different cations (Li+, K+ and Ca2+) and anions (F-, NO3- and SO42-), the phenomenon was revealed that the cation adsorption capacity of Li+ > K+ > Ca2+ captured by SnO2/CNT-HC and the anion adsorption capacity of F- > NO3- > SO42- adsorbed by activated carbon. These results show that SnO2/CNT-HC should be one of realistic electrode materials for HCDI.