Three-dimensional hierarchical porous carbon with a bimodal pore arrangement for capacitive deionization

In this work, three-dimensional hierarchical porous carbon (3DHPC) has been prepared via a double-template strategy with a colloidal crystal SiO2 as the hard template as well as a triblock copolymer as the soft template and its capacitive deionization (CDI) behavior in a NaCl aqueous solution was investigated for the first time. The resultant 3DHPC exhibits a bimodal porous structure with numerous mesopores defined in the well-interconnected macroporous walls. The unique pore architecture, resulting from an effective combination of the mesopores and macropores, presents a higher surface area as well as an improved electronic conductivity, which are quite beneficial for a high CDI performance. The electrochemical behaviors of the prepared electrodes were evaluated by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge measurements and 3DHPC shows great superiority when used as the CDI electrode. Moreover, the dependence of the CDI performance on the ion size and valence were also investigated in salt solutions with various cations and anions. Briefly, ions with a smaller hydrated radius and higher valence ensure a stronger electrostatic force onto the 3DHPC electrode, associated with an improved electrosorption behavior. Also, the desalination performance and regeneration behavior of the electrodes were evaluated by batch mode CDI apparatus. The high desalination capacity and excellent regeneration performance render the 3DHPC electrode a great potential in the CDI process.