First author by Jingjing Lei
Corresponding author: Ma Jie
Communication unit: Tongji University
Research at a glance
Recently, the Ma Jie team of Tongji University reported an electrodeionized Ti3C2TxMXene/carbon nanofiber multifunctional electrode with antifouling activity in Chemical Science. Fouling, corrosion and biological fouling have a huge economic impact and potential safety hazards for industrial circulating cooling water systems. Through the rational design and construction of electrodes, capacitive deionization (CDI) technology is expected to solve these three problems at the same time. Flexible self-supporting Ti3C2Tx MXene/carbon nanofiber membrane prepared by electrospinning for use as a multifunctional CDI electrode with high-performance antifouling and antibacterial activity. Bridging two-dimensional (2D) Ti3C2Tx nanosheets with one-dimensional (1D) carbon nanofibers to form a three-dimensional (3D) interconnected conductive network structure accelerates the transport and diffusion kinetics of electrons and ions. At the same time, the open-cell backbone of carbon nanofibers anchors Ti3C2Tx, alleviating the self-stacking of Ti3C2Tx nanosheets and expanding the interlayer space of Ti3C2Tx nanosheets, thereby providing more ion storage sites. The electric double-layer pseudocapacitive coupling mechanism confers high salt rejection capacity (73.42±4.57 mg g-1 at 60 mA g-1), fast salt rejection rate (3.57±0.15 mg g-1 min-1 at 100 mA g-1) and longer cycle life, which is superior to other carbon and MXene-based electrode materials. More importantly, due to the ideal hydrophilicity, good dispersion and fully exposed sharp edges of Ti3C2Tx nanosheets, Ti3C2Tx/CNF-14 also has a high inactivation efficiency against E. coli, reaching 99.89% within 4 hours. This research focuses on the killing of microorganisms through the inherent properties of carefully designed electrode materials, becoming a new engine that triggers high-performance multifunctional CDI electrode materials for circulating cooling water treatment.
Key point analysis
Point 1: Synthesis of materials: In this paper, the authors prepared Ti3C2TxMXene/carbon nanofiber antibacterial and antifouling multifunctional electrodes for circulating cooling water treatment. Electrospinning technology disperses the key material MXene nanosheets and develops multifunctional electrodes with self-supporting capabilities.
Point 2: Unique three-dimensional structure: In this paper, the authors form a three-dimensional (3D) interconnected conductive network structure by bridging two-dimensional (2D) Ti3C2Tx nanosheets and one-dimensional (1D) carbon nanofibers to accelerate the transport and diffusion kinetics of electrons and ions. At the same time, the open-cell backbone of carbon nanofibers anchors Ti3C2Tx, alleviating the self-stacking of Ti3C2Tx nanosheets and expanding the interlayer space of Ti3C2Tx nanosheets, thereby providing more ion storage sites. The electric double-layer pseudocapacitive coupling mechanism confers Ti3C2Tx/CNF-14 membranes with high desalination capacity (73.42±4.57 mg g-1 at 60 mA g-1), fast salt rejection rate (3.57±0.15 mg g-1 min-1 at 100 mA g-1) and longer cycle life.
Point 3: Bactericidal mechanism: In this paper, Ti3C2Tx nanosheets have ideal hydrophilicity, good dispersion and fully exposed sharp edges, making Ti3C2Tx/CNF-14 have an impressive inactivation efficiency against E. coli, reaching 99.89% within 4 hours.
Illustrated guide
Figure 1. (a) Ti3C2Tx/CNF preparation schematic. TEM images of etched Ti3C2Tx(b), stripped Ti3C2Tx(c), and Ti3C2Tx/PAN(d). (e) SEM image of Ti3C2Tx/PAN and corresponding element distribution map.
Figure 2. (a) Optical image of spun nanofiber membranes with different Ti3C2Tx concentrations (cut diameter 25 mm). SEM images of PAN nanofiber membrane (b), Ti3C2Tx/PAN-1(c), Ti3C2Tx/PAN-3(d), Ti3C2Tx/PAN-5(e), Ti3C2Tx/PAN-10(f) and Ti3C2Tx/PAN-14(e). (i) water contact angle and (h) flexible optical image of Ti3C2Tx/CNF-14; (j) TGA curves of spun nanofiber membranes at different Ti3C2Tx concentrations.
Figure 3. XRD spectra (a), FTIR data (b), and Raman spectra (c) of the sample. (d) XPS total spectra for Ti3C2Tx/CNF-14, Ti3C2Tx/PAN-14 and PAN. High-resolution XPS spectra of C1s(e), O1s(f), N1s(g), F1s(h), and Ti2p(i) of Ti3C2Txx/CNF-14.
Figure 4.(a) CV curves of Ti3C2Tx/CNF-14 at different scan rates. (b) CV curves for CNF and Ti3C2Tx/CNF-14 at 50mV s-1. (c) GCD distribution of Ti3C2Tx/CNF-14 at different current densities. (d) GCD distribution of CNF and Ti3C2Tx/CNF-14 at 1000 mA g-1. (e) Nyquist diagram of CNF and Ti3C2Tx/CNF-14. (f) Long-term GCD trial of Ti3C2Tx/CNF-14 at 2 A g-1.
Figure 5. (a) Photographs of E. coli cultured on NA plates after 4 h treatment with thin film samples (0%, 1%, 3%, 5%, 10%, and 14% with reference samples CNF, Ti3C2Tx/CNF-1, Ti3C2Tx/CNF-3, Ti3C2Tx/CNF-5, Ti3C2Tx/CNF-10, and Ti3C2Tx/CNF-14, respectively). (b) Inactivation effect of all membrane samples on E. coli. E. coli suspension (membrane-free sample) in normal saline was used as a control. (c) Linear fit plot of disinfection kinetics based on Chick model. (d) Schematic diagram of Ti3C2Tx/CNF-14 inactivation of E. coli.
Figure 6. Ti3C2Tx/CNF-14 desalination capacity and desalination rate at different current densities (a), cut-off voltage (b) and initial NaCl concentration (c). (d) Cycling and regenerative performance of Ti3C2Tx/CNF-14 at 100 mA g-1. (e) Desalination capacity of CNF and Ti3C2Tx/CNF-14 at different current densities. (f) Comparison of the desalination performance of Ti3C2Tx/CNF-14 with other carbon and MXene-based electrode materials. (g) The mass and molar desalination capacity of Ti3C2Tx/CNF-14 for CaCl2, MgCl2 and KCl. (h) TDS removal capacity of Ti3C2Tx/CNF-14 for mixed ionic solutions (up) and circulating cooling water (down). The inset shows the change in conductivity. (i) Schematic diagram of Ti3C2Tx/CNF-14 capacitor deionization.
Figure 7. The difference in charge density of CNF and Ti3C2Tx interfaces adsorbed Na(a) and Cl(b). (c) Na and Cl adsorption energy of CNF, Ti3C2Tx and Ti3C2Tx/CNF. (d) DOS spectra of CNF, Ti3C2Tx and Ti3C2Tx/CNF.
conclusion
In summary, the authors prepared a multifunctional electrode for Ti3C2Tx MXene/carbon nanofiber flexible self-supporting membrane for high-performance capacitive deionization, antifouling, and antimicrobial activity.
1) The unique 3D configuration formed by 1D CNF bridging 2D Ti3C2Tx nanosheets gives Ti3C2Tx/CNF-14 improved toughness, hydrophilicity, electrochemical properties and full exposure of sharp edges.
2) As a CDI electrode, the prepared Ti3C2Tx/CNF-14 membrane cooperates with the electric double layer mechanism and pseudo-capacitive effect, providing high desalination performance.
3) In addition, Ti3C2Tx/CNF-14 showed interesting antibacterial activity against E. coli.
This work provides new inspiration for enriching the selection range of CDI electrode materials, and has a positive effect on expanding the application of CDI in circulating cooling water treatment.
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参考文献：Jingjing Lei, Fei Yu, Haijiao Xie, Jie Ma. Ti3C2Tx MXene/Carbon Nanofiber Multifunction Electrode for Electrodeionization with Antifouling Activity. Chemical Science
2023 . DOI: 10.1039/d2sc06946f