An integrated large-scale and vertically aligned Co(OH)2 nanosheet@graphite paper electrode for high performance capacitive deionization of saline water

Capacitive deionization (CDI) based on the principle of electrochemical double layers has emerged as a prospective water treatment technology to challenge the water scarcity. Herein, a novel integrated CDI electrode comprised of large-scale and vertically aligned Co(OH)2 nanosheets on the GP matrix (Co(OH)2@GP) has been prepared successfully via a facile hydrothermal strategy for the first time. The texture analyses such as TEM, SEM, XPS, XRD and N2 adsorption indicated that well-grown and interconnected Co(OH)2 nanosheets on the GP matrix ensured the electrode a high specific surface area (207.62 m2/g) and superior open pore network. The electrochemical performance investigated by the CV, EIS and GC techniques revealed that the Co(OH)2@GP electrode combing the merits of Co(OH)2 nanomaterial and GP efficiently obtained the amazing specific capacitance of 411.02 F/g, good electric conductivity and favourable cyclability. Moreover, the CDI behaviour of Co(OH)2@GP electrode evaluated by the batch mode experiments in the 300 mg/L of NaCl solution demonstrated an ultrahigh salt removal capacity of 48.21 mg/g and excellent regeneration ability. The highly simplified electrode processing, free binder and outstanding CDI performance render the Co(OH)2@GP electrode a promising candidate in the highly efficient CDI application.