Optimizing carbon electrode spray coating for scalable redox electrodialysis systems

Redox-mediated electrodialysis (redox-ED) is a promising desalination technology that substitutes water splitting with sustainable redox reactions, thereby improving energy efficiency and reducing operational costs. However, the scalability of conventional porous carbon electrodes-such as activated carbon cloth and felt-is hindered by poor potential distribution and limited structural tunability. In this study, we propose a scalable electrode fabrication method using spray coating of activated carbon, carbon black, and polyvinylidene fluoride (PVDF) binder onto titanium mesh substrates (3 × 3 cm²) with binder contents ranging from 2 to 6 g (AC2–AC6). Among these, the AC5 electrode showed the best performance, delivering a specific capacity of 570.6 mAh/g—nearly double that of AC2—with an enlarged specific surface area (1361.6 to 1877.5 m²/g) and electrochemical active surface area (6.03 to 8.63 cm²) reduced charge transfer resistance (1.8 to 0.9 Ω). AC5 also optimized a salt removal rate of 1295.3 mmol/m²/h, charge efficiency of 98.9 %, and energy consumption of 117 kJ/mol. Importantly, this work provides the first demonstration of successfully scaling spray-coated electrodes to a practical dimension (15 × 6 cm², 120-fold larger) and integrating them into a 12-pair stacked redox-ED system.

This study envisions the spray coating as a transformative fabrication approach for redox-ED, offering a simple, tunable, and industry-ready pathway toward large-scale, high-performance, and economically viable desalination.