Preparation And Modification Of Activated Carbon Electrode And Its Capacitive Desalination Performance

Capacitive deionization（CDI）technology has been attracted increasing research attention due to the ever-growing water pollution.CDI can effectively remove dissolved salts from brackish water in a low-energy-consumption and eco-friendly way.Generally,a pair of porous electrodes is used in one CDI unit with an external applied potential to electrically adsorb the cations and anions from the salty water.The ions are captured and stored in the electrical double layer formed on the surface of the porous el ectrodes.As the electrodes are saturated,the circuit is shorted to realize the regeneration and the captured ions are released to bulk solution.Many carbon materials,such as activated carbon（AC）,carbon nanotubes（CNTs）,carbon nanofibers（CNFs）,carb on aerogel,graphene,have been investigated as CDI electrode.Among these materials,AC is likely the best choice as electrode material for commercialized CDI application due to its scalable manufacturing,favorable stability and reasonable cost.However,it is a remaining challenge to fabricate AC electrode with excellent mechanical stability,high specific surface area and high conductivity for practical applications.On one hand,the use of a newly developed organic-inorganic hybrid binder is reported to fabricate a robust AC electrode for CDI.Besides,the introduction of silicate into a resin binder can significantly alleviate mechanical stress,relieve rigidity,and improve the water tolerance of the AC electrode.The obtained electrode possesses a specific capacitance of 52 F·g^-1 and a high electrosorption capacity of 14.6 mg·g^-1 in Na Cl solution with an initial conductivity of 2000μS·cm^-1.Thanks to the enhanced flexibility and stability,a cylinder-plate disk CDI device(containing 60 pairs of AC electrodes,177 cm^-2 for each side of one electrode),displaying a 10 L·h^-1 of capacity for salty water treatment,was constructed as a demonstrator.On the other hand,we purposely devoted to electrode engineering by in-situ growth of CNTs arrays on activated carbon layer to achieve robust CDI electrodes with both high conductivity and high CDI performance.Such fluffy and entangled CNT networks can preserve ionic diffusion channels,well contacting of ACs particles and function as superhighways for electr ons transfer,therefore endowing AC electrodes with outstanding CDI behaviors,including a large output capacitance of 83.7 F·g^-1 and a low equivalent distributed resistance（EDR）of 0.02Ωin 0.5 M Na Cl neutral solution.Furthermore,the obtained electrode possesses a high electrosorption capacity of 15.6 mg·g^-1,a high charge efficiency of 82%,and a negligible CDI performance decay in long term cyclic period in Na Cl solution with an initial conductivity of 2000μS·cm^-1,indicating a very high electrosorption capacity and a low energy cost.The results show that the CNT grafted AC electrode can find great potential in practical application of CDI technology.Our work provides an effective technology for preparing high performance AC electrodes,which is enormously valuable in CDI technology,as well as can be essentially extended to industrial scale production for water purification.