Efficient and Durable Sodium, Chloride-doped Iron Oxide-Hydroxide Nanohybrid-Promoted Capacitive Deionization of Saline Water via Synergetic Pseudocapacitive Process

Coordination Confined Silver-Organic Framework for High Performance Electrochemical Deionization

Silver (Ag) is deemed a promising anode material for capacitive deionization (CDI) due to its high theoretical capacity and efficient selectivity to Cl-. However, the strong volume change during the conversion reaction significantly undermines the cycling performance of the Ag electrode. Additionally, achieving well-dispersed Ag in the active matrix is challenging, as Ag electrodes prepared by conventional thermal reduction tend to agglomerate. Herein, the organic linker confinement strategy is proposed, applying metal-organic framework (MOF) chemistry between Ag nodes and organic ligands to construct Ag-based MOF. The uniform dispersion of Ag at the molecular level, confined in the organic matrix, efficiently enhances the utilization of active sites, and strengthens the interfacial stability of Ag. Consequently, the Ag-MOF for the CDI anode exhibits an excellent Cl- removal capacity of 121.52 mg g-1 at 20 mA g-1 in 500 mg L-1 NaCl solution, and a high Ag utilization rate of 60.54%. After 100 cycles, a capacity retention of 96.93% is achieved. Furthermore, the Cl- capture mechanism of Ag-MOF is elucidated through density functional theory (DFT) calculations, ex situ XRD, ex situ Raman and XPS. This ingenious electrode design can offer valuable insights for the development of high-performance conversion electrodes for CDI applications.

Biomimetic Mineralization Synthesis of Flower-Like Cobalt Selenide/Reduced Graphene Oxide for Improved Electrochemical Deionization

Rationally and precisely tuning the composition and structure of materials is a viable strategy to improve electrochemical deionization (EDI) performances, which yet faces enormous challenges. Herein, an eco-friendly biomimetic mineralization synthetic strategy is developed to synthesize the flower-like cobalt selenide/reduced graphene oxide (Bio-CoSe2 /rGO) composites and used as advanced sodium ion adsorption electrodes. Benefiting from the slow and controllable reaction kinetics provided by the biomimetic mineralization process, the flower-like CoSe2 is uniformly constructed in the rGO, which is endowed with robust architecture, substantial adsorption sites and rapid charge/ion transport. The Bio-CoSe2 /rGO electrode yields the maximum salt adsorption capacity and salt adsorption rate of 56.3 mg g-1 and 5.6 mg g-1 min-1 respectively, and 92.5% capacity retention after 60 cycles. These results overmatch the pristine CoSe2 and irregular granular CoSe2 /rGO synthesized by a hydrothermal method, proving the structural superiority of the Bio-CoSe2 /rGO composites. Furthermore, the in-depth adsorption kinetics study indicates the chemisorption nature of sodium ion adsorption. The structures of the Bio-CoSe2 /rGO composites after long term EDI cycles are intensively studied to unveil the mechanism behind such superior EDI performances. This study offers one effective method for constructing advanced EDI electrodes, and enriches the application of the biomimetic mineralization synthetic strategy.

Synergistic Promotion of the Photocatalytic Preparation of Hydrogen Peroxide (H2 O2 ) from Oxygen by Benzoxazine and Si─O─Ti Bond

Hydrogen peroxide (H2 O2 ) is considered one of the most important chemical products and has a promising future in photocatalytic preparation, which is green, pollution-free, and hardly consumes any non-renewable energy. This study involves the preparation of benzoxazine with Si─O bonds via the Mannich reaction, followed by co-hydrolysis to produce photocatalysts containing benzoxazine with Si─O─Ti bonds. In this study, a benzoxazine photocatalyst with Si─O─Ti bonds is synthesized and characterized using fourier transform infrared spectroscopy, nuclear magnetic resonance, and X-ray photoelectron spectroscopy. The size and elemental distribution of the nanoparticles are confirmed by transmission electron microscopy and scanning electron microscopy. The photocatalytic synthesis of H2 O2 is tested using the titanium salt detection method, and the rate is found to be 7.28 µmol h-1 . Additionally, the catalyst exhibits good hydrolysis resistance and could be reused multiple times. The use of benzoxazine with Si─O─Ti bonds presents a promising experimental and theoretical foundation for the industrial production of H2 O2 through photocatalytic synthesis.

Comprehensive Study on the Ion-Selective Behavior of MnOx for Electrochemical Deionization

Manganese oxide is an effective active material in several electrochemical systems, including batteries, supercapacitors, and electrochemical deionization (ECDI). This work conducts a comprehensive study on the ion-selective behavior of MnOx to fulfill the emptiness in the energy and environmental science field. Furthermore, it broadens the promising application of MnOx in the ion-selective ECDI system. We propose a time-dependent multimechanism ion-selective behavior with the following guidelines by utilizing a microfluidic cell and the electrochemical quartz crystal microbalance (EQCM) analysis. (1) Hydrated radius is the most critical factor for ions with the same valence, and MnOx tends to capture cations with a small hydrated radius. (2) The importance of charge density rises when comparing cations with different valences, and MnOx prefers to capture divalent cations with a strong electrostatic attraction at prolonged times. Under this circumstance, ion swapping may occur where divalent cations replace monovalent cations. (3) NH4+ triggers MnOx dissolution, leading to performance and stability decay. The EQCM evidence has directly verified the proposed mechanisms, and these data provide a novel but simple method to judge ion selectivity preference. The overall ion selectivity sequence is Ca2+ > Mg2+ > K+ > NH4+> Na+ > Li+ with the highest selectivity values of βCa//Li and βCa//Na around 3 at the deionization time = 10 min.

Fabrication of magneticα-Fe2O3/Fe3O4heterostructure nanorods via the urea hydrolysis-calcination process and their biocompatibility with LO2and HepG2cells

β-FeOOH nanorods were prepared via the urea hydrolysis process with the average length of 289.1 nm and average diameter of 61.2 nm, while magneticα-Fe2O3/Fe3O4heterostructure nanorods were prepared via the urea calcination process withβ-FeOOH nanorods as precursor, and the optimum conditions were the calcination temperature of 400 °C, the calcination time of 2 h, theβ-FeOOH/urea mass ratio of 1:6. The average length, diameter, and the saturation magnetization of the heterostructure nanorods prepared under the optimum conditions were 328.8 nm, 63.4 nm and 42 emu·g-1, respectively. The Prussian blue test demonstrated that the heterostructure nanorods could be taken up by HepG2 cells, and cytotoxicity tests proved that the heterostructure nanorods had no significant effect on the viabilities of LO2 and HepG2 cells within 72 h in the range of 100-1600μg·ml-1. Therefore, magneticα-Fe2O3/Fe3O4heterostructure nanorods had better biocompatibility with LO2 and HepG2 cells.

Strong interface coupling boosting hierarchical bismuth embedded carbon hybrid for high-performance capacitive deionization

Capacitive deionization (CDI) is regarded as a promising desalination technology owing to its low cost and environmental friendliness. However, the lack of high-performance electrode materials remains a challenge in CDI. Herein, the hierarchical bismuth-embedded carbon (Bi@C) hybrid with strong interface coupling was prepared through facile solvothermal and annealing strategy. The hierarchical structure with strong interface coupling between the bismuth and carbon matrix afforded abundant active sites for chloridion (Cl^-) capture, improved electrons/ions transfer and the stability of the Bi@C hybrid. As a result of these advantages, the Bi@C hybrid showed a high salt adsorption capacity (75.3 mg/g under 1.2 V), salt adsorption rate and good stability, making it a promising electrode material for CDI. Furthermore, the desalination mechanism of the Bi@C hybrid was elucidated through various characterizations. Therefore, this work provides valuable insights for the design of high-performance bismuth-based electrode materials for CDI.

Surface redox pseudocapacitance boosting Fe/Fe3C nanoparticles-encapsulated N-doped graphene-like carbon for high-performance capacitive deionization

The practical application of carbon anode in capacitive deionization (CDI) is greatly hindered by their poor adsorption capacity and co-ion effect. Herein, an N-doped graphene-like carbon (NC) decorated with Fe/Fe₃C nanoparticles composite (Fe/Fe₃C@NC) with large specific surface area and plentiful porosity is fabricated via a facile and scalable method, namely sol-gel method combined with Fe-catalyzed carbonization. As expected, it exhibits superior CDI performance as a Cl-storage electrode, with Cl^- adsorption capacity as high as 102.3 mg g^-1 at 1000 mg L^-1 Cl^- concentration and 1.4 V voltage, and a stable capacity of 68.5 mg g^-1 for 60 cycles in 500 mg L^-1 Cl^- concentration and 100 mA g^-1 current density. More importantly, on the basis of electrochemical tests, ex-situ X-ray diffraction, ex-situ X-ray photoelectron spectroscopy (XPS), and XPS analysis with argon ion depth etching, it is revealed that the chlorine storage mechanism of the Fe/Fe₃C@NC electrode is dominated by the surface-related redox pseudocapacitance behavior of Fe²⁺/Fe³⁺ couple occurring on or near the surface, enabling fast and reversible ion storage. This work proposes an economical and environmentally friendly general method for the design and development of high-performance Cl-storage electrodes for CDI, and offers an in-depth insight into the Cl^- storage mechanism of Fe decorated carbon electrodes, further promoting the development of CDI technology.

Enhanced Pseudo-Capacitance Process in Nanoarchitectural Layered Double Hydroxide Nanoarrays Hollow Nanocages for Improved Capacitive Deionization Performance

Layered double hydroxides (LDHs) are perceived as a hopeful capacitive deionization (CDI) faradic electrode for Cl^- insertion due to its tunable composition, excellent anion exchange capacity, and fast redox activity. Nevertheless, the self-stacking and inferior electrical conductivity of the two-dimensional structure of LDH lead to unsatisfactory CDI performance. Herein, the three-dimensional (3D) hollow nanocage structure of CoNi-layered double hydroxide/carbon composites is well designed as a CDI anode by cation etching of the pre-carbonized ZIF-67 template. C/CoNi-LDH has a unique 3D hollow nanocage structure and abundant pore features, which can effectively suppress the self-stacking of LDH sheets and facilitate the transport of ions. Moreover, the introduced amorphous carbon layer can act as a conductive network. When employed as the CDI anode, C/CoNi-LDH exhibited a high Cl^- removal capacity of 60.88 mg g^-1 and a fast Cl^- removal rate of 18.09 mg g^-1 min^-1 at 1.4 V in 1000 mg L^-1 NaCl solution. The mechanism of the Cl^- intercalation pseudo-capacitance reaction of C/CoNi-LDH is revealed by electrochemical kinetic analysis and ex situ characterization. This study provides vital guidance for the design of high-performance electrodes for CDI.