Achieving an efficient redox-flow battery with high-conductivity electrospun carbon fiber for wastewater reclamation and seawater desalination

A redox-flow battery (RFB) has been established for continuous ion separation based on reversible redox reactions of the Fe(CN)63−/4− electrolyte. Herein, electrospun carbon fibers (CFs) with tailor-made properties were developed at different carbonization temperatures. With a carbonization temperature of 900°C, the CF (CF-900) showed a high degree of graphitization (Id/Ig = 0.92) and low electrode resistance. The cyclic voltammetry curve of CF-900 was composed of evident redox peaks with a high current level, revealing good electrochemical reversibility and high electrochemical activity of the redox reactions. With the CF-900 electrode, a high average salt removal rate (ASRR) of 97.5 μg/min/cm2 was achieved at 0.4 V while desalinating 10 mM NaCl, which was 1.4-fold higher than in the absence of the CF electrode. Moreover, the addition of the CF-900 electrode greatly improved the charge efficiency (96%) with a relatively low energy consumption of 0.0112 kWh/mol. The technical feasibility of RFB was assessed in terms of quantifying the ASRR for wastewater reclamation and seawater desalination. The application of high-conductivity CF-900 electrode demonstrated high ASRR (148.3 μg/min/cm2 for wastewater reclamation and 81.6 μg/min/cm2 for seawater desalination) with low energy consumption, making the strategy promising for achieving an efficient redox-flow battery process.