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

Highly Efficient Capacitive Removal of Heavy Metal Ions from Wastewater via In Situ π-π Stacking Covalent Organic Frameworks on Graphene Oxide Sheets

Capacitive deionization (CDI) is a promising technology for heavy metal wastewater purification but is limited by traditional carbon or Faradaic materials with low adsorption capacity, slow ion diffusion, poor selectivity, and inferior long-term cycling stability. Covalent organic frameworks (COFs) are recognized as highly anticipated porous materials, enable the construction of a stationary framework with superior structural properties, and provide numerous pores for ion transport in CDI applications. Herein, we synthesized a Schiff-based polymerized TOB-DAQ COF uniformly coated on graphene oxide (GO) sheets by a solvent-thermal in situ self-assembly strategy, leveraging π-π stacking interactions. These synthesized materials exhibit high efficiency and selectivity for heavy metal ion removal in complex and high-salinity solutions, enabled by their abundant active sites, rapid ion diffusion, and enhanced specific capacity. Crucially, conjoint material structural characterization and computational analysis of the electrostatic potential energy and adsorption energy barriers within the expanded framework elucidate the synergistic removal mechanism. This mechanism is attributed to central pore adsorption and carbonyl oxygen (-C═O) complexation. This study demonstrates the potential of COF materials to advance CDI-based wastewater treatment.

Carboxylated cellulose nanocrystals mediated flower-like zinc oxide for antimicrobial without activation of light

Conventional light-driven antimicrobial strategies of zinc oxide (ZnO) are limited by inadequate illumination in dark environments. In this study, carboxylated cellulose nanocrystals (MCNC) mediated flower-like ZnO (C0.1@Z) with self-promoted reactive oxygen species release under dark is fabricated. The adsorption of Zn2+ ions on MCNC prompts the growth of ZnO along the (002) crystal plane, forming a flower-like hybrid with superior dispersibility and oxygen vacancies compared to MCNC-free ZnO, which exposes the (100) plane. MCNC serves as an electron donor, increasing oxygen adsorption and electron transfer in C0.1@Z. Consequently, the generation of superoxide anions through oxygen reduction without photoirradiation is significantly boosted, thereby amplifying in-dark antimicrobial activity of C0.1@Z. Incorporating 2.5 % of C0.1@Z into pulp to prepare optimal antimicrobial paper (P-C@Z2.5) results in the prominent bactericidal and fungicidal effects against Staphylococcus aureus (99.8 %), Escherichia coli (99.9 %), Aspergillus niger (12.9 mm inhibition zone), and Botrytis cinerea (11.6 mm inhibition zone) in the absence of light. Additionally, P-C@Z2.5 exhibited low toxicity to cells and significantly extended the shelf life of blueberries to over 21 days. Overall, this work provides a promising approach for designing an effective antimicrobial material in the absence of light to address bacterial colonization of food during dark storage.

The Simpler the Better: Ultrafast Air-Plasma Synthesis of 3D Crosslinked Graphene Nanoscroll-Nanosheet Aerogels at Room Temperature for Capacitive Deionization

Graphene nanoscroll (GNS) is an important 1D tubular form of graphene-derivative materials, which has garnered widely attention. However, conventional fabrication methods commonly suffer from complex processing and time-consuming. Herein, with graphene oxide (GO) as a precursor, the study puts forward a facile air-plasma synthesis strategy to fabricate 3D graphene nanoscroll-nanosheet aerogels (GSSA). It is demonstrated that without using any chemical additives, a highly efficient reduction-exfoliation-scrolling process can be achieved all-in-one at room temperature within 1 s. The GNSs "grew" from 2D graphene sheets and firmly cross-linked them together, and they not only provide a shortcut path for electron transport but also act as intrinsic spacers to prevent restacking of graphene sheets. When using as an electrode material for capacitive deionization (CDI), GSSA exhibits excellent merits of salt-removal performance. These findings open a new pathway to large-scale synthesis of high-quality and high-purity GNS-based materials with promising applications in CDI and beyond.

A highly stable full-polymer electrochemical deionization system: dopant engineering & mechanism study

Electrochemical deionization (ECDI) has emerged as a promising technology for water treatment, with faradaic ECDI systems garnering significant attention due to their enhanced performance potential. This study focuses on the development of a highly stable and efficient, full-polymer (polypyrrole, PPy) ECDI system based on two key strategies. Firstly, dopant engineering, involving the design of dopants with a high charge/molecular weight (MW) ratio and structural complexity, facilitating their effective integration into the polymer backbone. This ensures sustained contribution of strong negative charges, enhancing system performance, while the bulky dopant structure promotes stability during extended operation cycles. Secondly, operating the system with well-balanced charges between deionization and concentration processes significantly reduces irreversible reactions on the polymer, thereby mitigating dopant leakage. Implementing these strategies, the PPy(PSS)//PPy(ClO4) (PSS: polystyrene sulfonate) system achieves a high salt removal capacity (SRC) of 48 mg g-1, an ultra-low energy consumption (EC) of 0.167 kW h kgNaCl-1, and remarkable stability, with 96% SRC retention after 104 cycles of operation. Additionally, this study provides a detailed degradation mechanism based on pre- and post-cycling analyses, offering valuable insights for the construction of highly stable ECDI systems with superior performance in water treatment applications.

Ultrathin nitrogen-doped carbon Ti3C2Tx-TiN heterostructure derived from ZIF-8 nanoparticles sandwiched MXene for high-performance capacitive deionization

Rational design of high-performance electrode materials is crucial for enhancing desalination performance of capacitive deionization (CDI). Here, ultrathin nitrogen-doped carbon/Ti3C2Tx-TiN (NC/MX-TiN) heterostructure was developed by pyrolyzing zeolite imidazolate framework-8 (ZIF-8) nanoparticles sandwiched MXene (ZSM), which were formed by assembling ultrafine ZIF-8 nanoparticles with size of 20 nm on both sides of MXene nanosheets. The introduction of ultrasmall ZIF-8 particles allowed for in situ nitridation of the MXene during pyrolysis, forming consecutive TiN layers tightly connected to the internal MXene. The two-dimensional (2D) heterostructure exhibited remarkable properties, including high specific surface area and excellent conductivity. Additionally, the resulting TiN demonstrated exceptional redox capability, which significantly enhanced the performance of CDI and ensured cycling stability. Benefiting from these advantages, the NC/MX-TiN exhibited a maximum adsorption capacity of 45.6 mg g-1 and a steady cycling performance in oxygenated saline water over 50 cycles. This work explores the rational design and construction of MXene-based 2D heterostructure and broadens new horizons for the development of novel CDI electrode materials.