Application of the macrohomogeneous line model for the characterization of carbon aerogel electrodes in capacitive deionization

Capacitive deionization (CDI) is a conceivable alternative desalination technology. Among the carbon materials studied as the deionizing electrode, carbon aerogels are a promising material due to their high surface area, structural designability and low resistivity. When evaluating carbons for CDI, their electrochemical properties are a crucial variable making the characterization of such properties vital. In this work we apply a macrohomogenous model to evaluate carbon aerogels activated with CO ₂ for various periods and varying Resorcinol/Catalyst, R/C, ratios during synthesis for estimation of their effective surface areas and pore sizes from an electrochemical standpoint. The porosities and structural properties of carbon aerogels were evaluated by nitrogen porosimetry, STEM, SEM and Electrochemical Impedance Spectroscopy (EIS). Results showed that the effective electrochemical surface areas calculated from the EIS were a small fraction of the areas estimated by nitrogen porosimetry, indicating that primarily the mesoporosity was utilized for deionization. Characteristic pore sizes calculated by the model were also close to the mesopore sizes estimated by the nitrogen adsorption isotherms, STEM and SEM measurements. Such results demonstrate the validity and value of the macrohomogenous model for evaluating effective electrochemical properties important for CDI applications.