Exceptional capacitive deionization desalination performance of hollow bowl-like carbon derived from MOFs in brackish water

Abstract

As a bright technology for desalinating brackish water, the desalination ability of capacitive deionization (CDI) has been limited by the electrode materials. However, it was still a challenge to adjust the construction of CDI electrode material to improve the salt removal ability. Here, nitrogen-doped hollow bowl-like carbon (HBC) has been successfully constructed in ZIF-8 by facile templating approaches. Physical measurements displayed that HBC had a hollow bowl-like structure, a certain number of nitrogen-containing groups and high specific surface area (1244 m2 g−1). These unique features made HBC have high capacitance (210.7F g−1), remarkable cycle stability and low charge transfer resistance in electrochemical double layer capacitors, indicating its promising application in CDI desalination. Due to the abundant ion accumulation active sites and rapid ion diffusion of HBC materials, provided by unique characteristics of regular hollow bowl-like structure, microporous dominated structure, interconnected channels and nano-scale wall thickness, HBC showed high salt removal ability of 28.06 mg g−1 with 1.2 V in 0.5 g L-1 NaCl solution. Besides, HBC exhibited excellent average salt ion adsorption rate (1.56 mg g−1 min−1) and initial salt adsorption capacity of 90% after 20 cycles.