Tailoring B, N-Enriched Carbon Nanosheets via a Gelation-Assisted Strategy for High-Capacity and Fast-Response Capacitive Desalination

Abstract

Designing high-performance carbonous electrodes for capacitive deionization with remarkable salt adsorption capacity (SAC) and outstanding salt adsorption rate (SAR) is quite significant yet challenging for brackish water desalination. Herein, a unique gelation-assisted strategy is proposed to tailor two-dimensional B and N-enriched carbon nanosheets (BNCTs) for efficient desalination. During the synthesis process, boric acid and polyvinyl alcohol were cross-linked to form a gelation template for the carbon precursor (polyethyleneimine), which endows BNCTs with ultrathin thickness (∼2 nm) and ultrahigh heteroatoms doping level (14.5 atom % of B and 14.8 atom % of N) after freeze-drying and pyrolysis. The laminar B, N-doped carbon enables an excellent SAC of 42.5 mg g–1 and fast SAR of 4.25 mg g–1 min–1 in 500 mg L–1 NaCl solution, both of which are four times as much as those of activated carbon. Moreover, the density functional theory (DFT) calculation demonstrates that the dual doping of B and N atoms firmly enhances the adsorption capacity of Na+, leading to a prominent chemical SAC for brackish water. This work paves a new way to rationally integrate both conducive surface morphology and systematic effects of B, N doping to construct high-efficiency carbonaceous electrodes for desalination.

Spinel Nickel Ferrite on Metal–Organic Framework-Derived Porous Carbon as a Robust Faradaic Electrode for Enhanced Flow Capacitive Deionization

“…NiFe 2 O 4 @PC-500, having a unique porous architecture, large surface area, and electrical conductivity, was employed as flow electrodes in the FCDI cell (Figure S11). The initial deionization performance of all electrodes was examined by assembling of FCDI cells with a concentrated aqueous solution of NaCl (1.5 g/L) . At the OCP, no change in salt concentration was detected (Figure S12).…”

“…The initial deionization performance of all electrodes was examined by assembling of FCDI cells with a concentrated aqueous solution of NaCl (1.5 g/L). 36 At the OCP, no change in salt concentration was detected (Figure S12). Therefore, the capacitive performance of NiFe 2 O 4 @PC-500 was compared with those of commercial AC and pristine MIL-88(FeNi) by applying a potential of 0.8 V. As shown in Figure 2A, NiFe 2 O 4 @PC-500 exhibited the highest SAC of ∼14.9 mg/g when compared to those of AC (∼5.6 mg/g) and MIL-88(FeNi) (∼7.74 mg/g).…”

“…For instance, the specific energy consumption increased significantly from 0.82 to 8.72 kWh/m 3 with a change in potential from 0.8 to 1.6 V because of the electrode polarization at the higher applied potential (Figure S14). 36 The optimum potential was marked as 1.2 V, where ASRR, SR%, and ENRS attained the anticipated values, providing reasons to perform subsequent FDCI studies.…”