Multi-walled vanadium oxide nanotubes modified 3D microporous bioderived carbon as novel electrodes for hybrid capacitive deionization

Funding Sponsor

American University in Cairo

Author's Department

Chemistry Department

Third Author's Department

Physics Department

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https://doi.org/10.1016/j.seppur.2021.118597

Document Type

Research Article

Publication Title

Separation and Purification Technology

Publication Date

7-1-2021

doi

10.1016/j.seppur.2021.118597

Abstract

Herein, a promising rationally-designed, high surface area multi-walled vanadium oxide nanotubes (VOx NTs) with a large interlayer spacing (6.5 Å) has been demonstrated as a cathodic dopant for efficient hybrid capacitive deionization (c-HCDI). The VOx NTs enhanced the surface charge of the 3D microporous graphene-like carbon, derived from natural palm tree (CNPT), as verified by Raman profiles and potential of zero charge measurements. The CDI batch-fashion testing has been performed using large surface area electrodes (6 × 7 cm2) and 135 ml of saline NaCl electrolyte. Interestingly, the used c-HCDI showed high salt adsorption capacity (SAC) of 25.0 mg/g for 6 mM NaCl at 1.6 V compared to the symmetric capacitive deionization configuration (s-CDI) that is only sustaining 16.0 mg/g. Besides, the cell demonstrates efficient stable SAC regardless of the initial feed concentration (1.6–25 mM) of NaCl. The charge efficiency of the c-HCDI markedly raised by around 25% over s-CDI for 5 mM NaCl, indicating the improved permselective manner of sodium ion diffusion/intercalation at the VOx NTs/CNPT cathode. Most importantly, the c-HCDI demonstrates a superior salt adsorption retention of 94.7% after 50 successive charge/discharge cycles compared to s-CDI that showed a decline of 7% after only 15 cycles. The Improved surface charge and wettability together with the pseudocapacitive storage manner of the cathode composite illustrate the synergism obtained via the hybrid configuration.

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