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

Designinghigh-performance carbonous electrodes for capacitivedeionization with remarkable salt adsorption capacity (SAC) and outstandingsalt adsorption rate (SAR) is quite significant yet challenging forbrackish water desalination. Herein, a unique gelation-assisted strategyis 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 gelationtemplate for the carbon precursor (polyethyleneimine), which endowsBNCTs with ultrathin thickness (& SIM;2 nm) and ultrahigh heteroatomsdoping level (14.5 atom % of B and 14.8 atom % of N) after freeze-dryingand pyrolysis. The laminar B, N-doped carbon enables an excellentSAC 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 ofactivated carbon. Moreover, the density functional theory (DFT) calculationdemonstrates that the dual doping of B and N atoms firmly enhancesthe adsorption capacity of Na+, leading to a prominentchemical SAC for brackish water. This work paves a new way to rationallyintegrate both conducive surface morphology and systematic effectsof B, N doping to construct high-efficiency carbonaceous electrodesfor desalination.