Improved desalination by zinc oxide nanorod induced electric field enhancement in capacitive deionization of brackish water

• Theoretical study of increase in capacitance with metal oxide (ZnO) semiconductor • Facile growth of ZnO nanorods arrays on CDI electrodes as proof of principle • Demonstration of the enhancement in ACC capacitance • Marked reduction in power consumption and improvement in charge efficiency • 30% higher specific salt adsorption capacity (mg/g) was achieved.

Using a finite element model (FEM) we show that by the addition of a nanostructured dielectric material like ZnO nanorods on the top of conducting activated carbon cloth (ACC) electrode, we were able to increase the penetration depth and magnitude of the electric field in the surrounding NaCl liquid medium. The electric field distribution was shown to be dependent on the length and diameter of the nanorods, with shorter rods showing higher field strengths. ZnO nanorods were Table 1 Comparison between plain activated carbon cloth (ACC) and zinc oxide (ZnO) nanorod coated ACC (ZnO_ACC) with respect to active surface area, capacitance, salt removal capacity, energy consumption and charge efficiency. The desalination was performed at an applied potential of 1.6 V DC using a 1000 ppm NaCl solution at a flow rate of 3 ml/min. Material Surface area (m2/g) Specific capacitance (F/g) Average Desal. Eff. (%) Mg of salt/g of electrode Energy/mol of salt removed (J/mol) Charge efficiency (η %) 1 mV/s 10 mV/s 50 mV/s ACC ZnO_ACC 5.9 mg/g 7.7 mg/g 5 × 103 J 3.4 × 103 J 53% 78% Appendix A. Supplementary data Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.desal.2014.12.029.