Biomass-derived porous carbon anode for high-performance capacitive deionization

Abstract The carbon material derived from citrus peel was prepared via hydrothermal synthesis method with low amount of ZnCl2. The morphology and surface structure of the synthesized carbons were characterized by field emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and N2 adsorption/desorption isotherms measurements. The electrochemical and capacitive deionization performance of carbon materials were comparatively studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD). Compared with the materials activated with KOH or H3PO4, ZnCl2-activated carbon showed the best electrochemical double-layer characteristics, with the specific capacity of 120 F g−1. When being applied as anode in the capacitive deionization (CDI) cell, the desalination amount of 16 mg g−1 and the average salt adsorption rate (ASAR) of 0.67 mg g−1 min−1 were achieved, which is much higher than those of KOH- and H3PO4-activated materials. The desalination amount retained 80% after 35 cycles. The possible mechanism is proposed in light of X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) analysis. This work provides a facile and environmentally friendly method for the preparation of a green and low cost biomass derived porous carbon material by fruit waste with a low amount (1% mass) of activation regents for high performance capacitive deionization.