Membrane-free electrochemical deoxygenation of aqueous solutions using symmetric activated carbon electrodes in flow-through cells

By Holubowitch, Nicolas E.; Omosebi, Ayokunle; Gao, Xin; Landon, James; Liu, Kunlei
Published in Electrochimica Acta 2019

Abstract

An electrochemical cell using symmetric carbon cloth electrodes and flow-through geometry that removes more than 97% of incoming aqueous dissolved oxygen (DO) is presented. The electro-deoxygenation (EDO) cell achieves O2 removal by leveraging the high overpotential of oxygen evolution on activated carbon and its propensity to oxidize under anodic polarization in aqueous solution: oxygen is reduced at the cathode while water is oxidized and incorporated into surface oxide functional groups at the anode, effectively sequestering dissolved oxygen. Polarized electrodes promote the two-step reduction of DO resulting in some residual hydrogen peroxide in the effluent, which may be beneficial for certain applications. A subsequent cell is modified with Ni cathodes downstream to reduce all H2O2 to water for particularly sensitive applications; in this cell >99% of incoming DO could be removed to lower than 10 ppb. EDO cells, which currently employ sacrificial anodes, can deaerate 30 L g?1anode of water at an energy consumption of 1 kWh per 10,000 L; carbon anode replacement can recharge the cell. The technique is versatile, inexpensive, and environmentally friendly, deoxygenating solutions from dilute to seawater concentrations at flow rates beyond 50 ml min?1 (O2 flux = 10?4 mol s?1 m?2), more than 50x faster DO removal than similar technologies.

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