The transition metal-based layered double hydroxides (LDHs) have been extensively studied as promising functional nanomaterials owing to their excellent electrochemical activity and tunable chemical composition. In this work, using acetate anions (Ac–) as intercalating elements, the NiCo-LDH nanosheets arraying on Ni foam with different amounts of Ac– anion intercalation or volume of hydrothermal solution were prepared by a simple hydrothermal method. The optimized amount of Ac– anions expanded the interlayer space of LDH nanosheets from 0.8 to 0.94 nm. An ultrahigh specific capacity of 1200 C g–1 at 1 A g–1 (690 C g–1 without Ac– anions), an outstanding rate capability of 72.5% at 30 A g–1, and a cycle stability of 79.90% after 4500 cycles were mainly attributed to the higher interlayer spacing of Ac– anion intercalation. The enlarged interlayer spacing was beneficial for stabilizing the α-phase of LDHs and accelerating the electron transport and electrolyte penetration in the electrochemical reaction. This work sheds light on the mechanisms of the interlayer spacing regulation of NiCo-LDH nanosheets and offers a promising strategy to synthesize functional nanomaterials with excellent electrochemical performance via integrating their unique layered structure and interlayer anion exchange characteristics.

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Capacitive deionization is a promising electrochemical water treatment technology. Activated carbon is commonly used and its corresponding parameters have an important influence on the electrosorption performance. In this work, on account of the mass loadings of the electrodes (the thickness varies from 200 μm to 600 μm), symmetric and asymmetric cells are constructed to investigate the importance of mass loadings on electrochemical performance and desalination. The results show that the electrode with the thickness of 200 μm achieves the largest specific capacitance of 72.65 F g−1, and thicker electrodes in the symmetric cell can reach a lower specific capacitance. However, the electrochemical performance of a working electrode in an asymmetric cell can be improved with a thicker counter electrode. As for desalination performance in the symmetric cell, S200 achieves the highest salt adsorption capacity of 7.05 mg g−1 under 1 V cell voltage, and ion removal rate increases while electrode utilization reduces with increased mass loading. In an asymmetric cell, when the anode is fixed at 400 μm and the cathode thickness increases from 200 to 600 μm, the salt adsorption capacity, average salt adsorption rate and charge efficiency decreases from 6.33 mg g−1, 0.49 mg g−1 min−1, 44.77% to 3.27 mg g−1, 0.17 mg g−1 min−1, 16.14%, respectively (dropped by 48.34%, 65.31% and 63.95%, respectively). The oxidation status of the electrode surface as characterized by multiple techniques, indicates that the oxidation degree of the anode can be reduced with a thinner cathode. Ultimately, lowering the mass loading of the cathode is conducive to enhancing total desalination performance and cycling stability.