Low-energy consumption, free-form capacitive deionization through nanostructured networks

Capacitive Deionization (CDI) is a non-energy intensive water treatment technology. To harness the enormous potential of CDI requires improving performance, while offering industrially feasible solutions. Following this idea, the replacement of costly metallic components has been proposed as a mean of limiting corrosion problems. This work explores the use of nanostructured hybrid networks to enable free-form and metal-free CDI devices. The strategy consists of producing interpenetrated networks of highly conductive flexible carbon nanotube (CNT) fibre fabrics and nanostructured metal oxides, gamma Al2O3 and TiO2, through ultrasound-assisted nanoparticle infiltration and sintering. In the resulting hybrids, a uniform distribution of porous metal oxide is firmly attached to the nanocarbon network while the flexibility, high conductivity and low-dimensional properties of the CNTs are preserved. These electrodes present a high porosity (105-118 m(2) g(-1)), notably low electrical (<0,1 k Omega cm(2)) and low charge transfer resistance (4 Omega), thus enabling the infiltration of aqueous electrolytes and serving as current collector. In this work we built a large asymmetrical cylindrical CDI device solely made of these electrodes and conventional plastics. The cell provides, high average salt adsorption rates of 1.16 mg.g(-1) (AM).min(-1) (0.23 mg.g(CDIunit)(-1).min(-1)), low energy consumption (0.18 W h.g(salt)(-1)) and stable electrochemical performance above 50 cycles for brackish water desalination. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The study explores the use of nanostructured hybrid networks to create metal-free CDI devices with improved performance. The electrodes have high porosity, low electrical resistance, and stable electrochemical performance, making them suitable for brackish water desalination with low energy consumption.