Ultrasound-assisted preparation of electrospun carbon fiber/graphene electrodes for capacitive deionization: Importance and unique role of electrical conductivity

Abstract

The desalination performance of capacitive deionization (CDI) technology is governed by electrode material properties, such as specific surface area, pore size and structure, surface functional groups, electrode geometry, and electrical conductivity. However, few studies have been conducted regarding the impact of the electrical conductivity of electrode materials on the desalination performance of CDI. In this study, monolithic composite web electrodes are fabricated. These electrodes are composed of reduced graphene oxide/activated carbon nanofiber with tuned conductivity by using an ultrasound-assisted electrospinning method. Freestanding monolithic carbon nanofiber webs function as a framework that prevents graphene sheets from restacking. The conductive graphene network helps quickly transfer electrons across the matrix while the ions are efficiently stored in the pores of the electrodes; as a result, a high electrosorption capacity for NaCl of 9.2 mg/g is achieved. The electrical conductivity of the electrodes is correlated with the ion removal efficiency of desalination. Results show that the electrosorption capacity of desalination governed by the electric double-layer scheme can be improved by increasing the electrical conductivity of the electrodes. These findings may provide new insights into the design and fabrication of novel porous electrode materials and elucidate the importance and effects of electrode conductivity on CDI.