Carbon-Encapsulated CoFe Alloys with Cobalt-Induced Fe³⁺ Stability Achieving Enhanced Capacitive Desalination

The high theoretical capacity of iron-based materials, combined with the pseudocapacitance enhancement effect from redox processes, provides an effective strategy to improve the salt adsorption capability of carbon-based capacitive deionization (CDI) electrodes. However, the limited active sites of single-metal components restrict further enhancement of the capacitive performance. In this study, a bimetallic electrode comprising cobalt–iron alloy encapsulated in carbon nanofibers (CoFe-CNF) was developed. By optimizing the electronic structure via the synergistic effect of Co-Fe bimetals and utilizing a three-dimensional mesoporous carbon network to inhibit alloy phase transitions and accelerate ion diffusion, the CoFe-CNF electrode demonstrated an ultrahigh desalination capacity of 105.6 mg g–1 in 500 mg L–1 NaCl solution, representing 58.3% improvement compared to single-metal Fe-CNF, along with over 90% capacity retention after 60 cycles. Characterization confirmed that the Fe2+/Fe3+ redox couples synergistically drive Cl– adsorption through dynamic charge redistribution, while the carbon encapsulation structure effectively alleviates volume expansion and forms a stable interface layer. This research proposes a dual electronic-structural modulation strategy for designing high-capacity CDI electrodes, advancing the application of bimetallic synergistic mechanisms in seawater desalination.