Interlayer Structure and Chemistry Engineering of MXene-Based Anode for Effective Capture of Chloride Anions in Asymmetric Capacitive Deionization

Abstract

Negatively charged surfaces and readily oxidizabile characteristics fundamentally restrict the use of MXene building blocks as anodes for anion intercalation. Herein, by embedding bacterial cellulose nanofibers with conformal polypyrrole coating (BC@PPy) and populating them between MXene (Ti 3 C 2 T x ) interlayers, we enable the fabricated MXene/BC@PPy (MBP) composite films to be highly efficient anodes for Cl − -capturing in asymmetric capacitive deionization (CDI) systems. Performance gains are realized due to the surface electronegativity of MXene nanosheets becoming compensated by positively charged BC@PPy nanofibers, alleviating electrostatic repulsion, thus realizing reversible Cl − intercalation. More crucially, the anodization voltage of MBP is effectively enhanced as a result of the increase of the Ti valence state in MXene nanosheets with the addition of the BC@ PPy spacer. Furthermore, BC@PPy nanopillars effectively enlarge the interlayer space for facile Cl − de-/intercalation, improve the vertical electron transfer between loosely deposited MXene nanosheets, and perform as additional active materials for Cl − -capturing. Consequently, the MBP anode exhibits a promising desalination capacity of up to 17.56 mg g −1 at 1.2 V with a high capacity retention of 94.6% after 30 cycles in an asymmetric CDI system. This work offers a simple and effective strategy to unlock the application potential of MXene building blocks as anodes for Cl − -capturing in electrochemical desalination.

First-Principles Study of 2D Haeckelite C7N as a High-Capacity Anode for Post-Lithium-Ion Batteries

“…Although the C 7 N shows subtle differences among the studied metal batteries, it passes the criteria for being an anode of all Na, K, and Ca. Indeed, the C 7 N anode for a certain metal battery can be optimized using a variety of engineering methods at our disposal . Moreover, the synthesis of various stoichiometric ratios of carbon–nitrogen compounds suggests that the synthesis of C 7 N is also feasible.…”

“…Indeed, the C 7 N anode for a certain metal battery can be optimized using a variety of engineering methods at our disposal. 73 Moreover, the synthesis of various stoichiometric ratios of carbon− nitrogen compounds 22 suggests that the synthesis of C 7 N is also feasible. To provide experimental evidence, we present a simulated scanning tunneling microscopy (STM) image of C 7 N in Figure S10.…”

MXene‐Based Capacitive Deionization–Strong Competitor Among Faradaic Electrode Systems: Current Status and Future Perspectives

“…To overcome the negative charge surface of Ti 3 C 2 T x MXene and facilitate reversible Cl − intercalation, Wu et al [211] . synthesized a Ti 3 C 2 T x /BC@PPy‐72.7 % freestanding composite film (zeta potential: +10.7 mV with respect to −31.6 mV for pure MXene) by populating MXene's interlayers with positively charged PPy‐coated 1D BC nanofibers (BC@PPy, zeta potential: +33.4 mV) (Figure 15g, h).…”

“…Most of the MXene-based intercalating electrodes are limited to host Na + except a few with Cl À storage/ removal. [208][209][210][211] Therefore, more attention is needed to prosper MXene-based Cl À capturing anode materials.…”

“…(h) Zeta potentials of the MXene, BC@PPy, and composite films with different % of BC@PPy loadings. Reprinted (adapted) with permission from ref [211],. Copyright (2023), American Chemical Society.…”