Villiform carbon fiber paper as current collector for capacitive deionization devices with high areal electrosorption capacity

Abstract

Capacitive deionization (CDI) has emerged as an attractive approach for desalination and water treatment for its high energy efficiency, low cost, and easy regeneration. Here, we report the preparation and application of villiform carbon fiber paper (v-CFP) as the current collector for CDI device with high areal electrosorption capacity. The v-CFP was prepared by thermal annealing and subsequent O2 plasma etching of the commercial pristine carbon fiber paper (p-CFP). With greatly improved surface area and hydrophilicity, the v-CFP itself showed an areal capacitance as high as 0.70 F·cm−2 in 0.5 M NaCl solution, and delivered an areal electrosorption capacity up to 122 and 400 mg·m−2 when feeding a NaCl solution with initial concentration of 50 and 3500 mg·L−1, respectively. Upon loading with additional electrode materials (EMs), e.g., graphene hydrogel, activated carbon, carbon nanotubes, and porous carbon spheres, the v-CFP/EM electrodes exhibited further improved areal electrosorption capacities, generally outperforming the corresponding p-CFP/EM electrodes by >2 times. Our studies demonstrate that proper surface treatment can largely improve the capacitance of the commonly used p-CFP current collector, making it greatly attractive in CDI devices.