Hierarchically ordered mesoporous carbons and silver nanoparticles as asymmetric electrodes for highly efficient capacitive deionization

Abstract

In this study, a novel capacitive deionization (CDI) technology by using silver nanoparticles and hierarchically ordered mesoporous carbons (HOMCs) as the anode and cathode electrodes, respectively, was developed to enhance the desalination efficiency of sodium ions. The TEM images show that HOMCs are 2-D hexagonal mesostructures with highly ordered 1-D strip-like channels and Ag is spherical with mean diameter of 30 nm. The electrochemical performance of HOMCs and activated carbons (ACs) show rectangular voltammograms at 5-100 mV s(-1), while two peaks with Faradic reaction occur for Ag electrode. The specific capacitance of HOMC electrode is 104.2 F g(-1) at 5 mV s(-1), which is 2.84 times higher than that of ACs. In addition, the asymmetric Ag parallel to HOMC electrodes show excellent electrosorption capacity and high stability toward sodium ion removal and the specific electrosorption capacity (SEC) is 356.3 and 251.6 mu mol g(-1) at 1.2 V in batch and continuous flowing solutions, respectively, which is 1.4-2.7 and 2.2-2.7 times higher than those of symmetric carbon-based electrodes. Results obtained in this study clearly indicate that the asymmetric Ag HHOMC electrode is a promising alternative nanomaterial which can open an innovative CDI technology to treat grey and brown waters that need high desalination efficiency. (C) 2016 Elsevier B.V. All rights reserved.