Porous carbon prepared by using ZIF-8 as precursor for capacitive deionization

In this work, porous carbon (PC) powders were prepared by carbonizing a zeolitic imidazolate framework (ZIF-8), and developed as the electrode material for capacitive deionization (CDI). The influence of carbonization temperature on the morphology, crystal structure, specific surface area and pore structure of PC powders were studied by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) and N2 adsorption–desorption isotherms. The results revealed that the carbonization temperature had remarkable effect on the textural of PC powders. The PC powder carbonized at 900 °C (PC-900) exhibited the highest specific surface area and micropore volume. In addition, the PC electrodes also were also fabricated using PC powders for the measurements of contact angle of glycerin, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The experimental results revealed that the PC-900 electrode had excellent wettability, the highest specific capacity and the lowest charge-transfer resistance. As expected, in CDI process, the PC-900 electrode exhibited a high CDI capacity up to 10.90 mg/g when the initial NaCl solution concentration is 500 mg/L, more than double that of commercial activated carbon (5.29 mg/g). Additionally, the PC-900 electrode also presented excellent regeneration performance for CDI.