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

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⁻¹ _anode 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.