Efficient Capacitive Deionization Using Natural Basswood-Derived, Freestanding, Hierarchically Porous Carbon Electrodes

Abstract

Carbon electrodes are of great importance in constructing high-performance capacitive deionization (CDI) devices. However, the use of conventional carbon electrodes for CDI is limited because of their poor mechanical stability and low mass loading. Herein, we report a binder-free, freestanding, robust, and ultrathick carbon electrode derived from a wood carbon framework (WCF) for CDI applications. The WCF inherits the unique structure of natural basswood, containing straightly aligned channels interconnected with highly ordered, open, and hierarchical pores. A CDI device based on thick WCF electrodes (1200 μm, equal to a mass loading of 50 mg cm) exhibits a remarkable areal salt adsorption capacity (SAC) of 0.3 mg cm, a high volumetric SAC of 2.4 mg cm, and a competitive gravimetric SAC of 5.7 mg g. Also, the good mechanical strength and water tolerance of the WCF electrodes improve the cycling stability of the CDI device. Finite element simulations of ion transport behavior indicate that the unique structure of the WCF substantially facilitates ion transport within the ultrathick CDI electrodes. This work provides a viable route to the rational design of freestanding and ultrathick electrodes for CDI applications and offers insights into the structure-performance relationship of CDI electrodes.

Toward sustainable desalination using food waste: capacitive desalination with bread-derived electrodes

“…We observed an average SAC as high as 12.7 mg g À1 at 1.2 V with a corresponding L of 0.67, which is competitive with recently reported values for FT electrodes, naturally-based electrodes, and freestanding CDI electrodes. Recent reports for freestanding CDI electrodes developed from basswood 25 and commercially available AC 27 have observed a SAC of 5.7 mg g À1 and 8.9 mg g À1 with a L of 0.30 and 0.48, respectively. We also calculated the areal and volumetric SAC for our bread-derived electrodes.…”

“…5 However, common electrode fabrication techniques using ACs require additional materials such as binders and current collecting mesh which can increase overall electrical resistance and material cost. [24][25][26] Reducing the material cost of the electrodes is a primary concern in CDI systems because it can be the largest expense in long-term full-scale operation. 26 Several recent studies have investigated the use of binder-free, freestanding electrodes to circumvent these issues.…”

“…26 Several recent studies have investigated the use of binder-free, freestanding electrodes to circumvent these issues. 25,27,28 We recently showed that an intact natural material, mangrove roots, could be carbonized and used as a FT-CDI electrode. 29 Although our results were exciting, the global supply of mangroves and their importance in natural habitats limits their applicability.…”

3D printed electrodes for efficient membrane capacitive deionization

“…It is clearly shown that they all possess the typical capacitor-like behaviour with no oxidation/reduction reactions; this suggests electrical double-layer behaviour as the main mechanism of ion adsorption on the surface of the electrodes. 19,35 Then, the specic capacitance of all electrodes was calculated, as shown in Fig. 2(b).…”

“…To maximize the efficiency of MCDI, the as-prepared electrodes should have the required functionality without any insulating components; unfortunately, the application of most of the preparation methods for the current electrodes is hindered by the major drawbacks such as the use of polymer binders, which may block the pathway for ions and increase the internal resistance of the electrodes, severely limiting the salt removal capacity. [17][18][19] However, a radical improvement in electrode performance might be achieved if various free-standing three-dimensional (3D) structures could be developed via alternative ways. To date, several routes have been proposed to prepare 3D structures such as carbon aerogels, 20 graphene aerogels, 12,21 carbon nanotube/graphene hybrid sponges, 11 activated carbon nanobers, 10,22,23 and redox-active nanoparticles/graphene aerogels.…”