ZrO2 nanofibers/activated carbon composite as a novel and effective electrode material for the enhancement of capacitive deionization performance

Abstract

Among the various forms of carbon materials, activated carbon still possesses the maximum attention as an optimum commercially available, cheap, and effective electrode material for the capacitive deionization desalination process. However, the well-known hydrophobicity and low specific capacitance limit its wide application. In this study, incorporation of zirconia nanofibers with activated carbon is reported as an effective and simple strategy to overcome the abovementioned problems. Typically, zirconia nanofibers, which were synthesized by the calcination of electrospun nanofiber mats, were added to the activated carbon to fabricate novel electrodes for the capacitive deionization units. In a single-mode cell, it was observed that the addition of the proposed metal oxide nanofibers distinctly enhanced the desalination process as the electrosorption capacity and the salt removal efficiency improved from 5.42 to 16.35 mg g⁻¹ and from 16.37% to 53.26% for the pristine and composite electrodes, respectively. However, the inorganic nanofiber content should be optimized; a composite having 10 wt% zirconia nanofibers with respect to the activated carbon showed the best performance. This distinct enhancement in the performance is attributed to the improvement in the wettability and specific capacitance of the electrode. Numerically, the water contact angle and the specific capacitance of the pristine and composite electrodes were found to be 145° and 26.5°, and 875 and 225 F g⁻¹, respectively. Overall, the present study strongly draws attention towards zirconia nanostructures as effective, cheap, environmentally friendly, and biologically safe candidates to enhance the performance of capacitive deionization electrodes.