Fig 1

SEM images of (A, B) KZnFC, (C, D) KZnFC-CNT, and (E) XRD patterns of KZnFC and KZnFC-CNT; (F) Full-spectra XPS of KZnFC and KZnFC-CNT; High-resolution of XPS spectra of (G) Zn 2p, (H) Fe 2p, (I) K 2p, (J) N 1s, and (K) C 1s."

Fig 2

(A) CV curves and (B) EIS fitting of KZnFC-CNT electrodes in 0.1 mol∙L−1 NaCl and CsCl solutions; (C) Specific capacitances and (D) capacitive contribution ratios of KZnFC-CNT electrodes at different scan rates."

Fig 3

(A) SEM images of the KZnFC-CNT electrode after post-activation; (B) Cs+ electrosorption capacity of the KZnFC-CNT electrode; (C) Corresponding Kim-Yoon plot; (D) Kinetics simulation results. XPS analysis of KZnFC-CNT electrodes at different stages: (E) Cs 3d and (F) Fe 2p spectra."

Fig 4

Time-dependent electrosorption capacities for Cs+ and Na+ ions in Cs-Na mixed solutions with a molar ratio of 1 : 1 at different voltages: (A) 0.6 V, (B) 0.8 V, (C) 1.0 V, (D) 1.2 V."

Fig 5

Time-dependent electrosorption capacities for Cs+ and Na+ ions in Cs-Na mixed solutions with different molar ratios of Cs(Ⅰ) : Na(Ⅰ): (A) 1 : 10, (B) 1 : 50, and (C) 1 : 100 at 1.0 V; (D) Corresponding Cs(Ⅰ) selectivity."

Fig 6

Full-region and partially enlarged XRD patterns of (A, E) KZnFC-CNT, (B, F) KZnFC*-CNT; XRD patterns of KZnFC*-CNT after electrosorption of (C, G) Na+ and (D) Cs+ ions; PDF standard cards of (H) Cs2Zn3[Fe(CN)6]2 and (I) Cs4Zn4[Fe(CN)6]3."

Fig 7

(A) Current variation during the activation process of the KZnFC-CNT electrode; (B) CV curve; (C) Capacitive contribution; (D) Cyclic charge-discharge testing for KZnFC*-CNT electrode."

Fig 8

(A) Energy variation during the simulated intercalation process of Cs+ and Na+ ions; Electron density maps for the adsorption models of (B) Na(Ⅰ) and (C) Cs(Ⅰ)."

Fig 9

Schematic diagram of selective Cs(Ⅰ) electrosorption by KZnFC-CNT."