Transition Metal Chemistry最新文献

Pyrochemical reprocessing has emerged as a crucial alternative to conventional hydrometallurgical methods for the reprocessing of spent nuclear fuel (SNF), particularly for high-burnup SNF from advanced reactors. Unlike the Plutonium Uranium Recovery by Extraction (PUREX) process, which encounters challenges with high-burnup SNF, pyrochemical reprocessing facilitates the direct processing of short-cooled fuel through electroreduction and electrorefining in molten salt. This review presents the research advancements in electroreduction and electrorefining within the context of pyrochemical reprocessing of SNF, systematically introducing the latest findings across five key areas: the electroreduction of oxide SNF pellets composed of various materials, anode materials, solid cathode materials, liquid cathode materials, and molten salt systems utilized in the electroreduction and electrorefining processes. Finally, the article summarizes the pressing issues currently facing electroreduction and electrorefining and proposes directions for future research.

The mechanism of carbon dioxide (CO₂) activation by the electrochemical reduction of molybdenum hexacarbonyl (Mo(CO)₆) in dry organic solvent was reinvestigated using IR spectroelectrochemistry (IR-SEC) combined with density functional theory (DFT) calculations. Cyclic voltammetry (CV) and IR-SEC experiments, carried out under inert atmosphere, confirmed that the stable pentacarbonyl dianion [Mo(CO)₅]²⁻ is readily formed at the reduction potential of the hexacarbonyl parent complex. In addition, IR-SEC monitoring of the reduction of Mo(CO)₆ in CO₂-saturated solution showed an absorption band ascribed to the formation of bicarbonate (HCO₃⁻), but no signs for the formation of formate (HCO₂⁻) or oxalate (C₂O₄²⁻). These experimental results were rationalized by DFT calculations on the coordination mode of CO₂ to [Mo(CO)₅]²⁻. Indeed, no stable structure could be calculated for the η¹-OCO isomer, whereas the optimized structure of the η²-CO₂ isomer was calculated to be energetically less stable than that of the η¹-CO₂ isomer, the latter being identified as a key intermediate for the selective formation of carbon monoxide (CO) and water (H₂O) upon O-protonation of the CO₂-adduct. This catalytic behavior is discussed here in terms of Mulliken atomic charge redistribution over the CO₂ binding and activation processes, and compared with what was previously reported for tetracarbonyl Mo-diimine complexes, where diimine ligands display “redox non-innocent” properties.

A sustainable solution to the intermittent nature of solar energy is using photocatalysts powered by sunlight to produce hydrogen from water, which offers a green substitute for fossil fuels. As the most promising semiconductor material for photocatalytic water splitting, TiO₂-based nanomaterials have received increasing attention from researchers in academia and industry in recent years. However, challenges remain to be addressed, such as a large bandgap, electron–hole recombination, preparation imperfections, and the possibility of excessive H2 production. Several approaches, including the addition of electron donors, doping, and defect engineering have been studied to overcome these constraints and enhance TiO₂ performance. Here, we provide a concise overview of the various techniques used to synthesize TiO₂-nanostructured photocatalyst. The present study also provides an overview of recent studies on the various factors influencing the photocatalytic process that produces H2 through water splitting. Important properties of photocatalysts include surface chemistry, particle size, pH, temperature, light source, electron donors, band gap, and the synthesis of both pure and doped TiO₂ photocatalyst materials are also discussed. Additionally, a comparative hydrogen generation rate is tabulated to get insight into the most effective synthesis process and type of TiO₂ for effective photocatalysis.

Graphical abstract

A new coordination compound of Ni(II) with nicotinamide (Nic) and 1,5-naphthalenedisulfonic acid (H₂NDS) of formula {[Ni(Nic)₂(H₂O)₄]NDS}.3H₂O (NNDSN) has been prepared by gel diffusion technique. SXRD data show that the compound crystallizes in triclinic space group P (overline{1 }). In the crystal structure, the Ni(II) ion is coordinated with two nicotinamide units through the nitrogen atom of pyridine ring and four water molecules. The distorted octahedral geometry of the six coordinate Ni(II) compound can be understood from the (angle) N–Ni–O (ranges from 86.59(7) to 93.41(7)°), (angle) O–Ni–O (88.63(7)° and 91.37(7)°) and difference in bond distances of Ni–O (2.0505(15) and 2.0533(16) Å) and Ni–N (2.1323(17) Å). 1,5-Naphthalenedisulfonate ions present in the crystal lattice balance the charge of Ni(II) ions. In the crystal structure, both coordinated and lattice water molecules, sulfonate groups of 1,5-naphthalenedisulfonate ions and NH₂ group of nicotinamide molecules are involved in intermolecular hydrogen bonding. These interactions further stabilize the crystal structure. FT-IR spectral studies show that SO₃⁻ group of 1,5-naphthalenedisulfonate ion, C = O and NH₂ groups of nicotinamide molecule are not involved in coordinate bond formation. In the UV–vis spectrum, the peaks corresponding to ³A_2g → ³T_1g (P) and ³A_2g → ³T_1g (F) transitions are observed at λ_max of 388 and 685 nm respectively. TG/DTG studies show that the crystal structure is stable up to 102 °C and the decomposition to NiO takes place through six stages. Photoluminescence studies show that the emission intensity of NNDSN can be quenched by Fe³⁺ ions. This method can be used for the sensing of Fe³⁺ ion at micro level concentration.

Transition metal dichalcogenides (M = Mo, W, Re) have gained significant attention for electrocatalytic applications in renewable energy due to their unique layered structures. However, their catalytic activity is often limited by the inert nature of basal planes, with active sites primarily located along the edges. In this study, we employed doping as a strategy to enhance the catalytic performance of Re_(1−x)W_xS₂ alloys by increasing the density of active sites. Using Re₂(µ-S)₂(S₂CNEt₂)₄ (1) and WS₃(S₂CNEt₂)₂ (2) as precursors, thin films were synthesized via aerosol-assisted chemical vapor deposition at 500 °C. Comprehensive characterization using powder X-ray diffraction, Raman spectroscopy, inductively coupled plasma optical emission spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy (TEM) confirmed the successful formation of Re_(1−x)W_xS₂ alloys. TEM analysis revealed a phase transition from 1T to 2H at W concentrations between 22.6 and 30.8%, indicating a structural evolution from the ReS₂ (1T) to WS₂ (2H) phase. Catalytic testing of both bulk and exfoliated materials in hydrogen evolution demonstrated that doping-induced structural modifications led to a higher density of catalytically active sites, significantly enhancing performance. These findings underscore the role of doping in tailoring the electronic and structural properties of TMDCs to optimize their catalytic efficiency, paving the way for their broader application in sustainable energy technologies.

The removal of organic pollutants, particularly textile dyes, using green and efficient methods is a key focus for researchers addressing environmental pollution. Advanced oxidation processes (AOPs), especially the Fenton-like process, have garnered significant attention for their ability to break down recalcitrant organic molecules into harmless byproducts, namely water and carbon dioxide, through the generation of hydroxyl radicals (^·OH). In this study, a heterogeneous Fenton-like catalyst, copper phosphate Cu₃(PO₄)₂, was synthesized in the presence of oxalate to achieve a unique morphology. The material was characterized by various physicochemical techniques, including TG, XRD, SEM, UV–Vis, XPS, photoluminescence (PL), and electrochemical impedance spectroscopy (EIS), to evaluate its potential for degrading Basic Yellow 28 (BY-28), a common organic dye of the textile industry. The degradation process was conducted at neutral pH with a BY-28 dye concentration of 20 mg L⁻¹ and a catalyst dose of 1 g L⁻¹. The catalytic activity is attributed to the high concentration of Cu²⁺ on the catalyst surface, which efficiently generates ^•OH radicals by activating hydrogen peroxide (H₂O₂).

Under hydrothermal conditions, a two-dimensional (2D) Anderson-type polyoxometalate-based framework {[Cu(dap)₂][Cu(dap)(H₂O)₂]₂[TeMo₆O₂₄]} (1, dap = 1,2-diaminopropane) was synthesized and characterized by single crystal X-ray diffraction analysis, elemental analysis, IR spectroscopy, electrochemical impedance spectroscopy and powder X-ray diffraction. Complex 1 features an unusual mixed-linkage 2D metal–organic network constructed from both single [Cu(dap)₂]²⁺ and double [Cu(dap)(H₂O)₂]²⁺ linkers. As a heterogeneous catalyst, 1 exhibited outstanding catalytic performance for the oxidation of 2-chloroethyl ethyl sulfide, achieving 99.1% conversion and 100% selectivity toward CEESO within 10 min at 35 °C, accompanied by excellent structural and catalytic stability. Moreover, 1 demonstrated promising electrochemical sensing properties of Cu²⁺ ions, showing a low limit of detection of 0.492 μM, a high sensitivity of 0.426 μA μM⁻¹ and good anti-interference ability.

DFT calculations were conducted to investigate bismuth–chalcogen di- and tri-iron carbonyl complexes: [E Bi Fen(CO)₆]⁻ (E = Se, Te, and n = 2, 3). The study employed the electron localization function and quantum theory of atoms in molecules to analyze the Fe–Fe, Fe–Se, Fe–Te, Fe–Bi, and Fe–CO bonding interactions. Additionally, a number of integral and local topological characteristics of the electron density related to these interactions were analyzed, along with the source function (SF). The topological properties and delocalization indices related to the Bi–Se and Bi–Te interactions, denoted as δ(Bi–E), suggest substantial direct Bi–E bonding in complexes 1 and 2, but only a minimal Bi–E interaction in clusters 3 and 4. The computed topological characteristics correspond well with the transition metal complexes documented in the existing literature. The topological parameters of the Fe–Fe bonds in complexes 1–4, where a localized bond has been identified, differ significantly from the Fe1–Fe2 interactions in clusters 3 and 4, where neither the bond critical point nor the bond path between the metal atoms could be identified. The SF contributions to the Fe–Fe bond critical points primarily arise from Bi atoms, which account for over 66.7%. Additionally, carbonyl O atoms contribute more than 15.7%, while E ligands contribute more than 7.6%. The topological properties and the delocalization indices associated with the Bi–Se and Bi–Te interactions, δ(Bi–E), imply significant direct Bi–E bonding in complexes 1 and 2, but only a very minor Bi–E interaction in clusters 3 and 4. The study also revealed notable π-back-donation from CO to Fe, as indicated by the Fe…OCO delocalization indices and SF calculations.

Tetracycline (TC) is a widely used antibiotic known for its significant antibacterial effects. However, its insufficient metabolism in living organisms and the accumulation of its residues have caused serious impacts on water sources and ecosystems. Photocatalytic technology, favored for its environmentally friendly, efficient, and non-polluting properties, has been applied to degrade TC. In this study, titanium dioxide nanoparticles (T6 and T32) were synthesized using titanium-oxo-clusters (Ti₆O₆ and Ti₃₂O₁₆) as the titanium source via a simple solvothermal method. Visible light degradation experiments revealed that the degradation rates of TC exceeded 92%, significantly outperforming commercial P25 (70%) and pure anatase TiO₂ (68%). Characterization by BET and XRD showed that the synthesized materials exhibited high specific surface areas (T6: 218 m²/g, T32: 207 m²/g) and good crystallinity. The surface complexes formed between the materials and TC enhanced the materials’ responsiveness to visible light (by broadening the absorption edge to 420 nm), playing a key role in the degradation process. Free radical trapping experiments and electron paramagnetic resonance (EPR) results indicated that ·O₂⁻, ¹O₂, and h⁺ were the primary reactive species involved in the degradation mechanism. Based on these findings, we propose a plausible degradation mechanism for the material. This study demonstrates that using titanium-oxo-clusters as a novel titanium source for TiO₂ synthesis can achieve highly efficient degradation of TC under visible light, offering innovative prospects for the development of future photocatalytic materials.

Considering environmental issues, which involve climate change and shortage of hydrocarbon resources, the usage of environmentally friendly technologies in energy generation has become essential worldwide. In this regard, water splitting is the best way of renewable energy source. Developing an efficient, high-performance and robust electrocatalyst became a significant goal to improve water splitting. For this purpose, we fabricated CdAl₂O₄@PANI (CAO@PANI) composite via hydrothermal approach for oxygen evolution reaction (OER). The CAO@PANI displayed varied morphologies, including nanoparticles of CAO affixed to PANI sheets, which enhance the surface area for adsorption of electrolyte ions. The electrocatalyst based on CAO@PANI nanostructure has enhanced efficiency relative to CAO as indicated by overpotential (η) of 192 mV at 10 mA/cm² j (current density) and remarkable durability (50 h). Additionally, CAO@PANI nanostructure exhibits an excellent Tafel plot (36 mV/dec) along with reduced charge transfer resistance (R_ct = 3.4 Ω). The fabricated catalyst also demonstrated notable double-layer capacitance (C_dl = 48 mF/cm²) and greater electrochemically active surface area (ECSA = 1200 cm²). The excellent outcomes may be associated to the combined effect of CAO and PANI, which has a distinctive π-conjugated framework and a variety of nitrogen species with lone pairs of electrons. This configuration facilitates a steady flow of OH⁻ ion and enhances its adsorption capacity on the surface of CAO@PANI, making it a remarkably effective and reliable catalyst for OER.