Synthesis and evaluation of composite δ-MnO2/C65 material properties for hybrid capacitive deionization application

Abstract

Capacitive deionization (CDI) has emerged as a revolutionary method for removing salt from solutions, gaining immense attraction due to its manifold benefits compared to the traditional desalination methods. This electrochemical technique offers a distinctive amalgamation of cost-effectiveness, energy efficiency, environmental sustainability, and operational simplicity. Moreover, the evolution of Hybrid Capacitive Deionization (HCDI) has furthered the possibilities within water desalination. By integrating carbon electrodes with those capable of redox reactions, HCDI displays significantly heightened ion adsorption efficiency in contrast to its precursor, conventional CDI which relies solely on carbon electrodes. The pivotal aspect revolving around materials not only facilitated redox reactions but also intricately entwined ions within their structural framework. This paper presented the synthesis of a layered δ-MnO2/C65 composite material using the sol-gel method. Characterization techniques of XRD, SEM and BET analyses showed critical insights into crystal phases, morphology, and structural attributes. Further assessment of its electrochemical properties via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) unequivocally underscores its potential in capacitive deionization applications. Notably, employing an asymmetric salt adsorption configuration with an activated carbon anode electrode derived from coconut shell (AC) in an AC||δ-MnO2/C65 model yielded exceptional results. The δ-MnO2/C65-1 composite emerged as the top performer showcasing the highest recorded salt adsorption capacity (SAC) of 38.4 mg/g, accompanied by an unparalleled salt adsorption rate (ASAR) of 2.1 mg/g.s-1. Detailed structural, morphological, and electrochemical analyses unequivocally identified the δ-MnO2/C65-1 composite as the optimal ratio, heralding superior efficacy and performance in salt removal and ion adsorption, a significant leap forward in capacitive deionization technology.