Enhanced Pseudo-Capacitance Process in Nanoarchitectural Layered Double Hydroxide Nanoarrays Hollow Nanocages for Improved Capacitive Deionization Performance
Dun Wei, Yiyun Cao, Lvji Yan, Haiyin Gang, Bichao Wu, Baixue Ouyang, Peng Chen, Yuxin Jiang, Haiying Wang
Abstract
Layered double hydroxides (LDHs) are perceived as a hopeful capacitive deionization (CDI) faradic electrode for Cl – insertion due to its tunable composition, excellent anion exchange capacity, and fast redox activity. Nevertheless, the self-stacking and inferior electrical conductivity of the two-dimensional structure of LDH lead to unsatisfactory CDI performance. Herein, the three-dimensional (3D) hollow nanocage structure of CoNi-layered double hydroxide/carbon composites is well designed as a CDI anode by cation etching of the pre-carbonized ZIF-67 template. C/CoNi-LDH has a unique 3D hollow nanocage structure and abundant pore features, which can effectively suppress the self-stacking of LDH sheets and facilitate the transport of ions. Moreover, the introduced amorphous carbon layer can act as a conductive network. When employed as the CDI anode, C/CoNi-LDH exhibited a high Cl – removal capacity of 60.88 mg g –1 and a fast Cl – removal rate of 18.09 mg g –1 min –1 at 1.4 V in 1000 mg L –1 NaCl solution. The mechanism of the Cl – intercalation pseudo-capacitance reaction of C/CoNi-LDH is revealed by electrochemical kinetic analysis and ex situ characterization. This study provides vital guidance for the design of high-performance electrodes for CDI.