Insights on the role of interparticle porosity and electrode thickness on capacitive deionization performance for desalination

Abstract

Capacitive deionization (CDI) is a promising desalination technology employing activated carbon as an electrode material. Although there have been many works concerning carbon preparation, much less attention has been paid to electrode development. Here, we report a comprehensive and systematic study of electrode preparation by blade-casting (DB) and free-standing (FS) techniques. The thickness, interparticle porosity, and hydrophilicity of the electrodes obtained by the different techniques affected their textural and electric properties, consequently influencing their CDI performance. Although there was no significant difference in the gravimetric salt adsorption capacity values (SACM between 14.7 and 16.9mgg−1), the volumetric salt adsorption capacities indicated superior performance of the FS electrode. However, when the SAC was considered together with the electrosorption and desorption kinetics, the DB electrode outperformed the FS electrode, mainly due to the fast kinetics ascribed to the improved mass transfer provided by the large interparticle voids of the DB carbon films. The results demonstrated that the faster kinetics provided by enhanced diffusion in thin electrodes with high interparticle porosity may be decisive for selection of the best electrode in CDI applications.