Nanoarchitectonics of vanadium carbide MXenes for separation and catalytic degradation of contaminants

Unraveling the role of V modified CoO in a wide pH range Fenton-like process

Building an effective heterogeneous Fenton catalyst over a broad pH range without the requirement for external energy input is still challenging. Herein, a vanadium-cobalt bimetallic catalyst (Co-V-8) are employed to extended a pH range of 3-9 by activating H2O2 as a Fenton-like catalyst. The Co-based Co-V-8 catalysts demonstrate high diclofenac sodium deterioration efficiency (98.2%) under both acidic and alkaline environments, and the kinetic reaction rate within 15 min could reach 0.288 min-1. Crucially, density functional theory (DFT) calculations imply that the Co-V-8 owned a narrower band gap and a higher Fermi level, which beneficial for quickening the electron transfer process. Results showed that the catalyst modified by V could introduce abundant oxygen vacancies, promote the decomposition of H2O2 via V3+ and V4+, and enhance the conversion of Co3+ and Co2+, accelerating the formation of ·OH, ·OOH, ·O-2 and electron transfer process. Additionally, Co-V-8 promoted the utilization rate of H2O2 exceeding 90% and exhibited exceptional catalytic ability in cleaning actual pharmaceutical wastewater. This research offers a sustainable separable and purification technology for wastewater remediation.

Recent advances in ultrasound-Fenton/Fenton-like technology for degradation of aqueous organic pollutants

Organic pollutants in water are a serious problem because of their widespread presence, harming the ecosystem and human health. Of the commonly used advanced oxidation processes, a hybrid of ultrasound and the Fenton/Fenton-like technology has received increasing attention in treatment of aqueous organic pollutants. This hybrid is effective in degradation of organic pollutants, but its application has not been summarised. Herein, first, the application and influencing factors of this hybrid technology for organic pollutants degradation are introduced. Second, the mechanism of its action is discussed. Third, the current challenges and future perspectives associated with this technology are proposed. This review provides valuable information regarding this technology, deepens the understanding of its mechanisms of organic pollutants degradation and provides a reference for its use in treatment of aquatic environments.

MXene/AgNW composite material for selective and efficient removal of radioactive cesium and iodine from water

Toxic fission products, such as cesium (137Cs) and iodine (129I) are of great concern because of their long half-lives and high solubility in water. The simultaneous removal of Cs and I using a single adsorbent is an area of increasing interest. In this study, MXene/silver nanowire (AgNW) composite was synthesized through physical mixing and employed for simultaneous removal of iodide (I-) and cesium (Cs+) ions from contaminated water. The MXene/AgNW composite demonstrated excellent adsorption capacities of 84.70 and 26.22 mg/g for I- and Cs+, respectively. The experimental data supported the hypothesis of multilayer adsorption of Cs+ owing to the inter-lamellar structures and the presence of heterogeneous adsorption sites in MXene. The interaction between I- and the AgNW involved chemisorption followed by monolayer adsorption. MXene/AgNW composite material exhibited promising results in the presence of competitive ions under extreme pH conditions. Thus, synthesized composite materials holds promising potential as an adsorbent for the remediation of radioactive liquid waste.

Fabrication of bimetallic-doped materials derived from a Cu-based complex for enhanced dye adsorption and iodine capture

In this work, we used Cu(II) ions, a bis-pyridyl-bis-amide ligand [N,N'-bis(4-pyridinecarboxamide)-1,2-cyclohexane (4-bpah)], and an aromatic dicarboxylic acid [1,4-cyclohexanedicarboxylic acid (H2CHDA)] to construct a 1D binuclear Cu-based complex, namely {[Cu3(4-bpah)(CHDA)3(H2O)]·2H2O}n (1). Moreover, we also developed a facile method to synthesize two monometallic/bimetallic-doped materials which were derived from the Cu complex (C-N-1 and C-V-1, which were doped with nitrogen and vanadium, respectively). The as-synthesized derived materials were fully characterized and the iodine sorption/release capabilities were investigated in detail. We performed iodine adsorption experiments on the two monometallic/bimetallic-doped materials and found that C-N-1 and C-V-1 possess highly efficient adsorption activities for the adsorption of iodine from solution. The C-N-1 and C-V-1 complexes exhibited remarkable adsorption capacities of 1141.60 and 1170.70 mg g-1, respectively, for iodine from a cyclohexane solution. Moreover, the dye adsorption properties of C-N-1 and C-V-1 were also investigated in detail. The obtained C-N-1 and C-V-1 exhibit effective dye uptake performances in water solution. The adsorption of Congo red (CR) on a single metal carbon material C-N-1 doped with heteroatoms reached equilibrium within 240 min and reached an adsorption capacity of 1357.00 mg g-1 and the adsorption capacities of C-V-1 for methylene blue (MB), gentian violet (GV), rhodamine B (RhB), and CR at room temperature were found to be 187.60, 190.60 and 108.10 and 1501.00 mg g-1 in 180 min, respectively. By comparison, we found that doping vanadium could play an important role in the adsorption processes. The adsorption capacity of C-V-1 (containing the vanadium in its structure) was relatively higher than that of C-N-1, which indicated that the introduction of non-noble metals may effectively tune the adsorption kinetics activity and the introduction of noble metals can change the surface electronegativity of porous carbon materials, thus leading to significantly improved adsorption capabilities.

Recent developments and perspectives of MXene-Based heterostructures in photocatalysis

Energy crises and environmental degradation are serious in recent years. Inexhaustible solar energy can be used for photocatalytic hydrogen production or CO2 reduction to reduce CO2 emissions. At present, the development of efficient photocatalysts is imminent. MXene as new two-dimensional (2D) layered material, has been used in various fields in recent years. Based on its high conductivity, adjustable band gap structure and sizable specific surface area, the MXene is beneficial to hasten the separation and reduce the combination of photoelectron-hole pairs in photocatalysis. Nevertheless, the re-stacking of layers because of the strong van der Waals force and hydrogen bonding interactions seriously hinder the development of MXene material as photocatalysts. By contrast, the MXene-based heterostructures composed of MXene nanosheets and other materials not only effectively suppress the re-stacking of layers, but also show the superior synergistic effects in photocatalysis. Herein, the recent progress of the MXene-based heterostructures as photocatalysts in energy and environment fields is summarized in this review. Particularly, new synthetic strategies, morphologies, structures, and mechanisms of MXene-based heterostructures are highlighted in hydrogen production, CO2 reduction, and pollutant degradation. In addition, the structure-activity relationship between the synthesis strategy, components, morphology and structure of MXene-based heterostructures, and their photocatalytic properties are elaborated in detail. Finally, a summary and the perspectives on improving the application study of the heterostructures in photocatalysis are presented.

Efficient Photocatalytic Reduction of Hexavalent Chromium by BiVO4-Decorated MXene Photocatalysts and Their Charge Carrier Dynamics

The synergistically MXene (Ti3C2Tx) co-catalyst-decorated BiVO4-based heterostructured photocatalysts have been synthesized by a hydrothermal approach with varied loading concentrations of MXene (Ti3C2Tx) to drive the hexavalent chromium reduction efficiently. The formation of the heterostructured photocatalyst was confirmed by the appearance of X-ray diffraction (XRD) peaks corresponding to the monoclinic BiVO4 phase and MXene (Ti3C2Tx) and also the antisymmetric (834 cm-1) and symmetric stretching (715 cm-1) of tetrahedral VO4 and D (1330 cm-1) and G (1570 cm-1) bands corresponding to MXene (Ti3C2Tx) in the Raman spectrum. The worm-like structures of BiVO4 nanocrystals grew onto the lamellar sheets of MXene (Ti3C2Tx), as shown by field emission scanning electron microscopy (FESEM), and has an increased surface area of 15.62 m2g-1 in the case of BVO-20-TC. X-ray photoelectron spectroscopy (XPS) analysis confirms the presence of V5+ and Ti3+states, and the uniform distribution of BiVO4 nanocrystals over lamellar sheets of MXene (Ti3C2Tx) is evident from energy-dispersive X-ray (EDX) analysis. The ultraviolet-diffuse reflectance spectroscopy (UV-DRS) spectra suggest a decrease in the band gap energy of BVO-20-TC to 2.335 eV, promoting a higher degree of visible light harvesting. Upon optimization, by varying the pH, the amount of the photocatalyst, and the concentration of Cr(IV), BVO-20-TC exhibits the highest photocatalytic efficiency (96.39%) while using a Cr(VI) concentration of 10 ppm at pH 2 and 15 mg of the photocatalyst, and the photoreduction of Cr(VI) to Cr(III) follows the pseudo-first-order reaction. The decrease in the PL intensity in BVO-20-TC reveals a faster transfer of electrons from MXene (Ti3C2Tx) to BiVO4. Further, the higher degree of band bending at the BiVO4/MXene (Ti3C2Tx) heterojunction, revealed from the Mott-Schottky analysis, facilitates efficient charge transfer and eventually faster and efficient photoreduction of Cr(VI) to Cr(III). The reusability and stability test undertaken for BVO-20-TC reveals that even after five cycles, the Cr (VI) photoreduction efficacy is retained. This work provides insights into photoreduction of Cr (VI) by using such heterostructures.

Visible-light-driven Oxygen Vacancy and Carbon Doping of C@TiO2-x Photocatalyst for Enhanced Pollutants Degradation Performance

Oxygen Vacancy (OVs) and carbon doping of the photocatalyst body will significantly enhance the photocatalytic efficiency. However, synchronous regulation of these two aspects is challenging. In this paper, a novel C@TiO2-x photocatalyst was designed by coupling the surface defect and doping engineering of titania, which can effectively remove rhodamine B (RhB) and has a relatively high performance with wide pH range, high photocatalytic activity and good stability. Within 90 minutes, the photocatalytic degradation rate of RhB by C@TiO2-x (94.1 % at 20 mg/L) is 28 times higher than that of pure TiO2 . Free radical trapping experiments and electron spin resonance techniques reveal that superoxide radicals (⋅O2- ) and photogenerated holes (h+ ) play key roles in the photocatalytic degradation of RhB. This study demonstrates the possibility of regulating photocatalysts to degrade pollutants in wastewater based on an integrated strategy.

Atomic-layered V2C MXene containing bismuth elements: 2D/0D and 2D/2D nanoarchitectonics for hydrogen evolution and nitrogen reduction reaction

The exploitation of two-dimensional (2D) vanadium carbide (V₂CT_x, denoted as V₂C) in electrocatalytic hydrogen evolution reaction (HER) and nitrogen reduction reaction (NRR) is still in the stage of theoretical study with limited experimental exploration. Here, we present the experimental studies of V₂C MXene-based materials containing two different bismuth compounds to confirm the possibility of using V₂C as a potential electrocatalyst for HER and NRR. In this context, for the first time, we employed two different methods to synthesize 2D/0D and 2D/2D nanostructures. The 2D/2D V₂C/BVO consisted of BiVO₄ (denoted BVO) nanosheets wrapped in layers of V₂C which were synthesized by a facile hydrothermal method, whereas the 2D/0D V₂C/Bi consisted of spherical particles of Bi (Bi NPs) anchored on V₂C MXenes using the solid-state annealing method. The resultant V₂C/BVO catalyst was proven to be beneficial for HER in 0.5 M H₂SO₄ compared to pristine V₂C. We demonstrated that the 2D/2D V₂C/BVO structure can favor the higher specific surface area, exposure of more accessible catalytic active sites, and promote electron transfer which can be responsible for optimizing the HER activity. Moreover, V₂C/BVO has superior stability in an acidic environment. Whilst we observed that the 2D/0D V₂C/Bi could be highly efficient for electrocatalytic NRR purposes. Our results show that the ammonia (NH₃) production and faradaic efficiency (FE) of V₂C/Bi can reach 88.6 μg h^-1 cm^-2 and 8% at -0.5 V vs. RHE, respectively. Also V₂C/Bi exhibited excellent long-term stability. These achievements present a high performance in terms of the highest generated NH₃ compared to recent investigations of MXenes-based electrocatalysts. Such excellent NRR of V₂C/Bi activity can be attributed to the effective suppression of HER which is the main competitive reaction of the NRR.

Emerging carbonate anion intercalated- ZnCr-layered double hydroxide/vanadium carbide nanocomposite: Sustainable design strategies based on disposal electrochemical sensor for diethofencarb fungicide monitoring

Diethofencarb (DFC) is widely used in agriculture to fight against plant fungal attacks and enhance food crop production. On the other hand, the National food safety standard has set the overall maximum residual limit (MRL) of DFC to be 1 mg/kg. Hence it becomes essential to limit their usage, and it is vital to quantify the amount of DFC present in real-life samples to safeguard the health and environmental well-being. Here, we introduce a simple hydrothermal procedure for preparing vanadium carbide (VC) anchored by ZnCr-LDH. The sustainably designed electrochemical sensor for the detection of DFC portrayed high electro-active surface area, conductivity, rapid-electron transport ratio, and high ion diffusion parameters. The obtained structural and morphological information confirms the enriched electrochemical activity of the ZnCr-LDH/VC/SPCE towards DFC. The ZnCr-LDH/VC/SPCE electrode has displayed exceptional characteristics with DPV resulting in a vast linear response (0.01-228 μM), and lower LOD (2 nM) with high sensitivity. Real-sample analysis was carried out to demonstrate the specificity of the electrode with an acceptable recovery in both water (±98.75-99.70%) and tomato (±98.00-99.75%) samples.

Application of nanoarchitectonics in moist-electric generation

The consumption of energy is an important resource that cannot be ignored in modern society. Non-renewable forms of energy, such as coal, natural gas, and oil, have always been important strategic resources and are always facing a crisis of shortage. Therefore, there is an urgent need for green renewable forms of energy. As an emerging green energy source, the moist-electric generator (MEG) has been studied in recent years and may become an energy source that can be utilized in daily life. Along with the advancement of technological means, nanoarchitectonics play an important role in MEG devices. This review aims to provide a comprehensive summary of the fundamentals of the MEG from the perspective of different material classifications and to provide guidance for future work in the field of MEGs. The effects of various parameters and structural designs on the output power, recent important literature and works, the mechanism of liquid-solid interactions at the nanoscale, and the application status and further potential of MEG devices are discussed in this review. It is expected that this review may provide valuable knowledge for future MEG research.

Molecule-to-Material-to-Bio Nanoarchitectonics with Biomedical Fullerene Nanoparticles

Nanoarchitectonics integrates nanotechnology with various other fields, with the goal of creating functional material systems from nanoscale units such as atoms, molecules, and nanomaterials. The concept bears strong similarities to the processes and functions seen in biological systems. Therefore, it is natural for materials designed through nanoarchitectonics to truly shine in bio-related applications. In this review, we present an overview of recent work exemplifying how nanoarchitectonics relates to biology and how it is being applied in biomedical research. First, we present nanoscale interactions being studied in basic biology and how they parallel nanoarchitectonics concepts. Then, we overview the state-of-the-art in biomedical applications pursuant to the nanoarchitectonics framework. On this basis, we take a deep dive into a particular building-block material frequently seen in nanoarchitectonics approaches: fullerene. We take a closer look at recent research on fullerene nanoparticles, paying special attention to biomedical applications in biosensing, gene delivery, and radical scavenging. With these subjects, we aim to illustrate the power of nanomaterials and biomimetic nanoarchitectonics when applied to bio-related applications, and we offer some considerations for future perspectives.

Generation of singlet oxygen over CeO2/K, Na-codoped g-C3N4 for tetracycline hydrochloride degradation in a wide pH range

Singlet oxygen (1O2) were widely studied for catalytic oxidation and photo dynamic therapy (PDT) and so on due to its unique properties, such as its long lifetime, wide pH tolerance,...

Porous carbon nanoarchitectonics for the environment: detection and adsorption

As a post-nanotechnology concept, nanoarchitectonics has emerged from the 20th century to the 21st century. This review summarizes the recent progress in the field of metal-free porous carbon nanoarchitectonics.