Mold-casting prepared free-standing activated carbon electrodes for capacitive deionization

Activated carbon (AC) electrodes applied in capacitive deionization (CDI) are usually prepared by coating activated materials on current collector, accompanying with low mass loading, poor areal salt adsorption capacity (SAC(A)) and undesired volumetric salt adsorption capacity (SAC(V)). Herein, we report preparation of free-standing AC electrodes by a simple mold-casting method. Unlike conventional coating methods, activated materials were well-dispersed together with binders to obtain a uniform suspension and then submitted for mold-casting preparation of electrodes. This new strategy helps to produce rational structure for porous free-standing AC electrodes by alleviating the blocking effect of pores. Obtained electrodes not only exhibit pretty good electrical conductivity and hydrophilicity, but also show excellent mechanical stability and water tolerance. The electrodes deliver both high SAC(A) of 0.49 mg/cm(2) and SAC(V) of 2.48 mg/cm(3). By virtue of the free-standing feature, a CDI device comprising 6 as-made units was built for demonstration, which exhibits a promising SAC(V) of 2.01 mg/cm(3) in NaCl aqueous solution. This work not only offers a simple method to prepare free-standing AC electrodes with extraordinary high mass loading (55 mg/cm(2)) and excellent salt adsorption capacity, but also provides good opportunity for large-scale application of CDI technology by substantially improving packing volumetric density. (C) 2019 Elsevier Ltd. All rights reserved.