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The recent discovery of MoB2 with a superconducting transition temperature (Tc) of up to 32 K at 100 GPa provides new insights into the metallization and subsequently high-Tc superconductivity of diborides, highlighting the potential of transition metals in these compounds. We herein re-evaluated the structure, mechanical, and superconducting properties of IrB4 under pressure up to 300 GPa using first-principles. Our calculations reveal that a new P21/c phase exhibiting a hardness of 15.75 GPa surpasses the stability of the C2/m structure identified through the particle swarm optimization at ambient pressure. Upon compressing, the P21/c phase transforms into an MgB2-type structure with a space group of P63/mmc at 62.5 GPa and then into the orthorhombic Cmca phase above 109 GPa. Unlike semiconductor behavior of the atmospheric pressure phase, the two high-pressure structures are metallic and superconducting, with Tc values of 29.90 for P63/mmc at 62.5 GPa and 13.45 K for Cmca at 125 GPa. Analysis of the electronic structure and electron–phonon coupling (EPC) reveals that the high Tc, similar to MgB2-type MoB2, stems from the Van Hove Singularities (VHS) near the Fermi level donated by transition metal Ir. The effect further enhances the EPC based on the boron contribution. More interestingly, pressure has little impacts on the position of the VHS. These findings provide a new platform for designing advanced high-Tc superconductors. [ABSTRACT FROM AUTHOR]

The recent discovery of MoB2 with a superconducting transition temperature (Tc) of up to 32 K at 100 GPa provides new insights into the metallization and subsequently high-Tc superconductivity of diborides, highlighting the potential of transition metals in these compounds. We herein re-evaluated the structure, mechanical, and superconducting properties of IrB4 under pressure up to 300 GPa using first-principles. Our calculations reveal that a new P21/c phase exhibiting a hardness of 15.75 GPa surpasses the stability of the C2/m structure identified through the particle swarm optimization at ambient pressure. Upon compressing, the P21/c phase transforms into an MgB2-type structure with a space group of P63/mmc at 62.5 GPa and then into the orthorhombic Cmca phase above 109 GPa. Unlike semiconductor behavior of the atmospheric pressure phase, the two high-pressure structures are metallic and superconducting, with Tc values of 29.90 for P63/mmc at 62.5 GPa and 13.45 K for Cmca at 125 GPa. Analysis of the electronic structure and electron–phonon coupling (EPC) reveals that the high Tc, similar to MgB2-type MoB2, stems from the Van Hove Singularities (VHS) near the Fermi level donated by transition metal Ir. The effect further enhances the EPC based on the boron contribution. More interestingly, pressure has little impacts on the position of the VHS. These findings provide a new platform for designing advanced high-Tc superconductors. [ABSTRACT FROM AUTHOR]

The recent development of accurate and efficient semilocal density functionals on the third rung of Jacob's ladder of density functional theory, such as the revised regularized strongly constrained and appropriately normed (r2SCAN) density functional, could enable rapid and highly reliable prediction of the elasticity and temperature dependence of thermophysical parameters of refractory elements and their intermetallic compounds using the quasi-harmonic approximation (QHA). Here, we present a comparative evaluation of equilibrium cell volumes, cohesive energy, mechanical moduli, and thermophysical properties (Debye temperature and thermal expansion coefficient) for 22 transition metals using semilocal density functionals, including the local density approximation (LDA), Perdew–Burke–Ernzerhof (PBE) and PBEsol generalized gradient approximations (GGAs), and the r2SCAN meta-GGA. PBEsol and r2SCAN deliver the same level of accuracies for structural, mechanical, and thermophysical properties. PBE and r2SCAN perform better than LDA and PBEsol for calculating cohesive energies of transition metals. Among the tested density functionals, r2SCAN provides an overall well-balanced performance for reliably computing cell volumes, cohesive energies, mechanical properties, and thermophysical properties of various 3d, 4d, and 5d transition metals using QHA. Therefore, we recommend that r2SCAN could be employed as a workhorse method to evaluate thermophysical properties of transition metal compounds and alloys in high throughput workflows. [ABSTRACT FROM AUTHOR]

In this research, we investigated different hybrid photocatalysts: Ni/Mo.S2/MOF-2@g-C3N4, Mo.S2/MOF-2@g-C3N4, Ni.S2/MOF-2@g-C3N4 and Ni/Mo.S2/MOF-2. These photocatalysts were synthesized using a solvothermal method by incorporating Ni.x/Mo.Sx, the heterojunction showed improved separation of photoinduced charges due to disparity in charge transfer. This resulted in a narrower energy band gap and excellent catalytic activity in photodegradation. The Ni/Mo.S2/MOF-2@g-C3N4 heterostructure demonstrated outstanding photocatalytic efficiency, with up to 91% degradation of methylene blue (MB). This significant degradation was driven by the generation of superoxide (O2•) and hydroxyl (•OH) radicals. The process adhered to pseudo-first-order kinetics and was effectively completed within 90 min of light exposure. Remarkably, the Ni/Mo.S2/MOF-2@g-C3N4 heterostructure displayed excellent stability, with only minimal performance degradation observed after five consecutive cycles. These results underscore the superior stability of the heterostructure. In summary, our research confirms that the Ni/Mo.S2/MOF-2@g-C3N4 heterojunction photocatalyst is a highly efficient material for the effective removal of methylene blue dye. [ABSTRACT FROM AUTHOR]

As typical dielectric materials, transition metal compounds have a broad potential in the field of stealth, but their application is still hampered by poor conductivity. In this study, based on the mechanism of electrostatic self-assembly of heteropolyacids and organic ligands, the electrostatic structures obtained after the introduction of different heteropolyacids into the conductive phase pyrrole are carbonized. On the one hand, the as-prepared transition metal compounds/carbon matrix nanocomposites produce synergistic effects and optimize impedance matching, and on the other hand, the formation of the abundant heterogeneous interfaces as well as the doping of the N, P heteroatoms induce the generation of interfacial polarisation and dipole polarisation, all of which provide the opportunities to produce composites with enhanced electromagnetic wave absorption properties. Unsurprisingly, the best synthesised sample, Mo 2 C/W 2 C/NPC, exhibits a significantly improved electromagnetic wave absorption performance, with an effective bandwidth of 5.7 GHz at a matched thickness of 2.5 mm, where the minimum reflection loss value of −54.5 dB is also achieved. The total effective bandwidth of the Mo 2 C/W 2 C/NPC-35 wt% is up to 10.5 GHz (7.3–17.8 GHz) via adjusting the matching thickness in the range of 1.7–3.5 mm. Therefore, this study reflects that dual transition metal compound/carbon based composite wave-absorbing materials provide a new material basis for the construction of high-performance absorption materials. [ABSTRACT FROM AUTHOR]

The two‐electron oxygen reduction reaction (2e‐ORR) for the sustainable synthesis of hydrogen peroxide (H2O2) has demonstrated considerable potential for local production of this environmentally friendly chemical oxidant on small, medium, and large scales. This method offers a promising alternative to the energy‐intensive anthraquinone approach, placing a primary emphasis on the development of efficient electrocatalysts. Improving the efficiency of electrocatalysts and uncovering their catalytic mechanisms are essential steps in achieving high 2e‐ORR activity, selectivity, and stability. This comprehensive review summarizes recent advancements in electrocatalysts for in‐situ H2O2 production, providing a detailed overview of the field. In particular, the review delves into the design, fabrication, and investigation of catalytic active sites contributing to H2O2 selectivity. Additionally, it highlights a range of electrocatalysts including pure metals and alloys, transition metal compounds, single‐atom catalysts, and carbon‐based catalysts for the 2e‐ORR pathway. Finally, the review addresses significant challenges and opportunities for efficient H2O2 electrosynthesis, as well as potential future research directions. [ABSTRACT FROM AUTHOR]

In recent decades, the chemistry of transition metal coordination compounds has undergone continuous development at both scientific and application levels. The diversity of metal(II) complexes, along with their structural features and physicochemical properties, makes them attractive for a wide range of applications. The dicyanamide ion (N(CN)2) has the ability to form various transition metal compounds characterized by different architectures and topologies. The interaction of π-electrons from the nitrile groups with the π-system of the central nitrogen may enable electron delocalization, potentially facilitating electron transfer between the metal centers through the bridging dicyanamide (dca) ligand. This review focuses on dca–Co(II) compounds and, after a brief introduction, the structural aspects and magnetic properties are analyzed in detail. [ABSTRACT FROM AUTHOR]

Transition metal compounds (TMCs) are potentially fruitful substitutes for noble metals for electrocatalytic splitting of water due to their intrinsic electrocatalytic activity, modifiable morphology, tunable electronic structure and their earth‐abundance. The combination of TMCs with graphene improves the dispersion of loaded catalysts, providing more catalytic active sites, enhancing the conductivity of hybrids, affording accelerated charge‐transfer kinetics, and minimizing catalyst bleaching, aggregation, and sintering under harsh reaction conditions. Additionally, graphene incorporation into TMCs modulates the electronic structure of active centers because of the synergistic interaction between them, thereby improving their catalytic performance. This review paper focuses on the recent progress made in designing different graphene‐transition metal‐based materials that can be used in the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and overall water splitting (OWS). In‐situ characterization methodologies and DFT calculations that facilitate catalyst development are discussed elaborately. Finally, the advancements made in the development of graphene‐supported transition metal compounds for use in a functional water electrolyzer have been explored. In conclusion, a few specific recommendations have been made about the current challenges related to the widespread production of effective HER/OER electrocatalysts for water electrolysis. [ABSTRACT FROM AUTHOR]

Transition metal sulfide compounds with high theoretical specific capacity and excellent electronic conductivity that can be used as cathode materials for secondary batteries attract great research interest in the field of electrochemical energy storage. Among these materials, MnSe2 garners significant interest from researchers due to its unique three-dimensional cubic structure and inherent stability. However, according to the relevant literature, the performance and cycle life of MnSe2 are not yet satisfactory. To address this issue, we synthesize MnSe2/CNTs composites via a straightforward hydrothermal method. MnSO4·H2O, Se, and N2H4·H2O are used as reactants, and CNTs are incorporated during the stirring process. The experimental outcomes indicate that the fabricated electrode demonstrates an initial discharge specific capacity that reaches 621 mAh g−1 at a current density of 0.1 A g−1. Moreover, it exhibits excellent rate capability, delivering a discharge specific capacity of 476 mAh g−1 at 10 A g−1. The electrode is able to maintain a high discharge specific capacity of 545 mAh g−1 after cycling for 1000 times at a current density of 2 A g−1. The exceptional electrochemical performance of the MnSe2/CNTs composites can be ascribed to their three-dimensional cubic architecture and the 3D CNT network. This research aids in the progression of aqueous Cu-ion cathode materials with significant potential, offering a viable route for their advancement. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) are important new energy storage devices. Due to the abundance of sodium and the similar operating principles of SIBs to lithium-ion batteries (LIBs), SIBs are considered as an important complementary technology to LIBs that will dominate the next generation of energy storage. However, large-scale application of SIBs is hindered by severe capacity decay and low rate capability. The actual capacity of batteries is closely related to the specific capacity of anode materials. Therefore, the development of high-capacity anode materials has become a key area of research for SIBs. Transition metal compounds can improve these problems due to their unique electronic band structure, good chemical adsorption ability, and excellent catalytic ability. Cobalt-based phosphide anode materials have the characteristics of high theoretical capacity, abundant reserves, and low prices, making them become promising anode materials for SIBs. Furthermore, adjusting the size and structure and combining with carbon-based or non-carbon-based materials can effectively alleviate the defects of cobalt-based phosphide electrodes, thereby improving the specific capacity, cyclic stability, and rate capability of SIBs. This review summarizes the recent research progress on cobalt-based phosphide anode materials for SIBs, including the current research status and future development prospects. [ABSTRACT FROM AUTHOR]

Five compounds, [Zn2(bpe)(BPTA)2(H2O)2] ⋅ 2H2O (1); [Zn(bpe)(BPTA)] (2); [Cd(bpe)(BPTA)H2O] (3); [Cd(BPTA) (bpmh)] ⋅ 2H2O (4); and Cu2(BPTA)2(bpmh)3(H2O)2] ⋅ 2H2O (5) were prepared employing 2,5‐bis(prop‐2‐yn‐1‐yloxy)terephthalic acid (2, 5 BPTA) as the primary ligand and 1,2‐di(pyridin‐4‐yl)ethane (4, 4′ bpe) (1–3) and 1,2‐bis(pyridin‐3‐ylmethylene)hydrazine (bpmh) (4–5) as the secondary ligands. Single crystal studies indicated that the compounds 1, 3 and 5 have two‐dimensional layer structures and compounds 2 and 4 three‐dimensional structures. The luminescence behaviour of the compounds 2 and 3 were explored for the sensing of metronidazole in aqueous medium. The studies indicated that the compounds can detect metronidazole in ppm level both in solution as well as simple paper strips. The Cu compound 5 was found to lose the coordinated water molecule at 100 °C without any structural change. The coordinatively unsaturated Cu‐centre were examined towards the Lewis acidic character by carrying out the Ullmann type C−C homocoupling reaction of the aromatic halide compounds. The compounds, 4 and 5, also have the Lewis basic functionality arising out the =N−N=, aza groups. The bifunctional nature of the coordination polymers (CP) was explored towards the Chan‐Lam coupling reaction between phenyl boronic acid and aniline derivatives in the ethanol medium. In both the catalytic reactions, good yields and recyclability were observed. The present studies illustrated the rich diversity that the transition metal containing compounds exhibit in extended framework structures. [ABSTRACT FROM AUTHOR]

[Display omitted] The application of Li-S batteries on large scale is held back by the sluggish sulfur kinetics and low synthesis efficiency of sulfur host. In addition, the preparation of catalysts that promote polysulfide redox kinetics is complex and time-consuming, reducing the cost of raw materials in Li-S. Here, a universal synthetic strategy for rapid fabrication of sulfur cathode and metal compounds nanocatalysts is reported based on microwave heating of graphene. Heat-sensitive materials can achieve rapid heating due to graphene reaching 500 ℃ within 4 s via microwave irradiation. The MoP-MoS 2 /rGO catalyst demonstrated in this work was synthesized within 60 s. When used for catalysts for Li-S batteries whose graphene/sulfur cathodes were also synthesized by microwave heating, enhanced catalytic effect for sulfur redox reaction was verified via experimental and DFT theoretical results. Benefiting from fast redox reaction (MoP), smooth Li+ diffusion pathways (MoS 2), and large conductive network (rGO), the assembled Li-S battery with MoP-MoS 2 /rGO-Add@CS displays a remarkable initial specific capacity, stable lithium anode and good cycle stability (in pouch cells) using this two-pronged strategy. The work provides a practical strategy for advanced Li-S batteries toward a wide range of applications. [ABSTRACT FROM AUTHOR]

Porous high-entropy transition metal compounds, an important type of ultra-high temperature material, have attracted increasing attention in the applications of extreme environments due to their low density, good thermal insulation and stable chemical properties. A robust, flame-retardant and high-temperature resistant high-entropy carbonitride (Ti 1/5 V 1/5 Mo 1/5 Nb 1/5 Ta 1/5)(C 0.55 N 0.45) (HECN) porous ceramic was synthesized and thoroughly characterized. It exhibited a porosity of 93.5 %, a compressive strength of 1.3 MPa and a good high-temperature stability up to 1673 K, which, along with its outstanding fire-retardancy, and low thermal conductivity (as low as 0.150 W m−1 K−1 at 298 K), made it a good candidate material for thermal insulation applications in ultra-high temperature environments. Moreover, the Density functional theory (DFT) calculations predict that the [N]/([C]+[N]) ratio in HECN foam affects its lattice thermal conductivity which is decreased by 67 % upon increasing the ratio from 0 to 1/2. [ABSTRACT FROM AUTHOR]

Recent experimental advances in ultrafast science have put different processes occurring on the electronic timescale below a few femtoseconds in focus. In the present theoretical work, we demonstrate how the transformation and propagation of the density matrix in the basis of irreducible spherical tensors can be conveniently used to study sub-few fs spin–flip dynamics in core-excited transition metal compounds. With the help of the Wigner–Eckart theorem, such a transformation separates the essential dynamical information from the geometric factors governed by the angular momentum algebra. We show that an additional reduction can be performed by the physically motivated truncation of the spherical tensor basis. In particular, depending on the degree of coherence, the ultrafast dynamics can be considered semi-quantitative in the notably reduced spherical basis when only the total populations of the basis states of the given spin are of interest. Such truncation should be especially beneficial when the number of high-spin basis states is vast, as it reduces computational costs. [ABSTRACT FROM AUTHOR]

The schematic diagram illustrates that the N -doped carbon (NC) shells enhance the stability against carbonitride corrosion by suppressing surface reconstruction during the oxygen evolution reaction (OER). [Display omitted] • N -doped carbon encapsulated multimetallic carbonitrides were synthesized using urea-based gel. • The core-shell structure provided enhanced stability against oxidation during the OER. • Online mass spectrometric studies confirm improved carbon stability against oxidation. Electrocatalytic water splitting is a promising solution for generating clean hydrogen. Transition metal compounds are among the most extensively investigated catalysts developed to date for water oxidation in alkaline media, a process also known as the oxygen evolution reaction (OER). However, the application of these catalysts was constrained by insufficient stability arising from surface oxidation and metal dissolution under high OER potential. In this work, we developed a facile approach using urea-based gel as the precursor of preparing a series of multimetallic carbonitride particles which were encapsulated by N -doped carbon (NC). In particular, (MoCoFeNiZr)CN@NC core–shell structure delivered a low overpotential of 246 mV at a current density of 10 mA cm−2 in 1 M KOH during OER. Importantly, operando differential electrochemical mass spectrometry (DEMS), together with multiple microscopic and spectroscopic analyses, indicated that the NC shells effectively maintained the crystalline stability of carbonitride via suppressing the surface reconstruction during catalysis. The highly graphitic NC also demonstrates excellent stability against oxidation. This work shows a promising strategy of stabilizing electrocatalyst at high anodic potential, paving the way for the development of robust electrode materials for energy conversion. [ABSTRACT FROM AUTHOR]

A unique polyaniline (PANI) electron bridge was integrated into the metal–organic frameworks (MOFs)/layer double hydroxides (LDHs) heterojunction to expedite electron transfer from MOFs to LDHs, facilitating electron accumulation at the metal sites within MOF and electron-deficient LDHs and thus guiding the dynamic reconstruction. [Display omitted] • MIL-88B(Fe)@PANI@NiCo LDH heterojunctions with built-in electric field is built. • The built-in electric field induces an asymmetric interfacial electron distribution. • The PANI can serve as electron bridge to boost the electron transfer. • The dynamic reconstruction of MIL-88B(Fe)@PANI@NiCo LDH can be controlled. Tailoring the dynamic reconstruction of transition metal compounds into highly active oxyhydroxides through surface electron state modification is crucial for advancing water oxidation, yet remains a formidable challenge. In this study, a unique polyaniline (PANI) electron bridge was integrated into the metal–organic frameworks (MOFs)/layer double hydroxides (LDHs) heterojunction to expedite electron transfer from MOFs to LDHs, facilitating electron accumulation at the metal sites within MOF and electron-deficient LDHs. This configuration promotes the surface dynamic reconstruction of LDHs into highly active oxyhydroxides while safeguarding the MOF from corrosion in harsh environments over extended periods. The optimized electronic structure modification of both MOFs and LDHs enhances reaction kinetics. The superior MIL-88B(Fe)@PANI@NiCo LDH catalyst achieved 10 mA∙cm−2 at an overpotential of 202 mV and demonstrated stable operation for 120 h at this current density. This research introduces an innovative approach for guiding electron transfer and dynamic catalyst reconstruction by constructing a PANI electron bridge, potentially paving the way for more efficient catalytic systems. [ABSTRACT FROM AUTHOR]

Diazoalkenes readily react with tert‐butylphosphaalkyne (tBuCP) and white phosphorus (P4) to afford novel phosphorus heterocycles, 3H‐1,2,4‐diazamonophospholes and 1,2,3,4‐diazadiphospholes. Both species represent rare examples of neutral heterophospholes. The mechanism of formation and the electronic structures of these formal (3+2) cycloaddition products were analyzed computationally. The new phospholes form structurally diverse coordination compounds with transition metal and main group elements. Given the growing number of stable diazoalkenes, this work offers a straightforward route to neutral aza(di‐)phospholes as a new ligand class. [ABSTRACT FROM AUTHOR]

The neural-network quantum states (NNQS) method is rapidly emerging as a powerful tool in quantum mechanisms. While significant advancements have been achieved in simulating simple molecules using NNQS, the ab initio simulation of complex solid-state materials remains challenging. Here in this work, we have adopted the periodic density matrix embedding theory to extend the NNQS method to deal with complex solid-state systems. Our approach notably reduces the computational problem size while maintaining high accuracy. We have validated the accuracy and efficiency of our method against traditional methodologies and experimental data in extended systems, and have investigated the magnetic ordering and charge density wave state in transition metal compounds. The findings from our research indicate that the integration of quantum embedding with intuitive chemical fragmentation can significantly enhance the NNQS simulation of realistic materials. [ABSTRACT FROM AUTHOR]

Transition metal disulfide compounds (TMDCs) emerges as the promising candidate for new‐generation flexible (opto‐)electronic device fabrication. However, the harsh growth condition of TMDCs results in the necessity of using hard dielectric substrates, and thus the additional transfer process is essential but still challenging. Here, an efficient strategy for preparation and easy separation‐transfer of high‐uniform and quality‐enhanced MoS2 via the precursor pre‐annealing on the designed graphene inserting layer is demonstrated. Based on the novel strategy, it achieves the intact separation and transfer of a 2‐inch MoS2 array onto the flexible resin. It reveals that the graphene inserting layer not only enhances MoS2 quality but also decreases interfacial adhesion for easy separation‐transfer, which achieves a high yield of ≈99.83%. The theoretical calculations show that the chemical bonding formation at the growth interface has been eliminated by graphene. The separable graphene serves as a photocarrier transportation channel, making a largely enhanced responsivity up to 6.86 mA W−1, and the photodetector array also qualifies for imaging featured with high contrast. The flexible device exhibits high bending stability, which preserves almost 100% of initial performance after 5000 cycles. The proposed novel TMDCs growth and separation‐transfer strategy lightens their significance for advances in curved and wearable (opto‐)electronic applications. [ABSTRACT FROM AUTHOR]

Electrophysiological monitoring is a commonly used medical procedure designed to capture the electrical signals generated by the body and promptly identify any abnormal health conditions. Wearable sensors are of great significance in signal acquisition for electrophysiological monitoring. Traditional electrophysiological monitoring devices are often bulky and have many complex accessories and thus, are only suitable for limited application scenarios. Hydrogels optimized based on nanomaterials are lightweight with excellent stretchable and electrical properties, solving the problem of high-quality signal acquisition for wearable sensors. Therefore, the development of hydrogels based on nanomaterials brings tremendous potential for wearable physiological signal monitoring sensors. This review first introduces the latest advancement of hydrogels made from different nanomaterials, such as nanocarbon materials, nanometal materials, and two-dimensional transition metal compounds, in physiological signal monitoring sensors. Second, the versatile properties of these stretchable composite hydrogel sensors are reviewed. Then, their applications in various electrophysiological signal monitoring, such as electrocardiogram monitoring, electromyographic signal analysis, and electroencephalogram monitoring, are discussed. Finally, the current application status and future development prospects of nanomaterial-optimized hydrogels in wearable physiological signal monitoring sensors are summarized. We hope this review will inspire future development of wearable electrophysiological signal monitoring sensors using nanomaterial-based hydrogels. [ABSTRACT FROM AUTHOR]

The seawater electrolysis for hydrogen production has a wide range of raw materials, which can effectively couple with marine new energy to reduce the cost of offshore electricity, and has become a hot topic in the hydrogen production industry. However, the deposition of Mg2+ and Ca2+, as well as the corrosion of chlorides on the electrolysis cell, hinder the large-scale application of seawater electrolysis hydrogen production technologies. Therefore, improving hydrogen production technologies and developing new electrode materials to reduce the impact of impurities in seawater have become the focus of research and development for seawater electrolysis hydrogen production. Firstly, the main components of seawater and their impacts on the performance and lifespan of seawater electrolysis systems were analyzed. The advantages and disadvantages of different electrolysis seawater hydrogen production technologies were discussed, as well as research progress. It is believed that electrolysis seawater hydrogen production technologies still mainly rely on hydrogen production after seawater purification. Then, the electrode materials for seawater electrolysis were summarized, including precious metal materials, transition metal compound catalytic materials, and new structural materials. Among them, transition metal compound catalytic materials have good development prospects. Finally, the challenges and prospects faced by the industrial application of seawater electrolysis hydrogen production technologies were discussed, and it is pointed out that combining the research results of efficient and long-life transition metal compound catalytic materials, as well as the hydrogen production technologies after seawater purification, will be the development direction of seawater electrolysis in the future. [ABSTRACT FROM AUTHOR]

Platinum-based catalysts exhibit outstanding electrocatalytic performance in the hydrogen evolution reaction (HER). However, platinum-based catalysts face significant challenges due to their rarity and high cost. This paper endeavors to shed light on a promising alternative: polyoxometalate (POM)-based catalysts, which possess significant potential for the synthesis of non-noble metal-based catalysts for the HER. Utilizing POMs as raw materials to assemble POM-derived materials, including POM-derived crystalline materials, metal sulfides, phosphides, carbides, nitrides, and so on, has emerged as an effective approach for the synthesis of hydrogen evolution electrocatalysts. This approach offers advantages in both stability and electrocatalytic performance. This comprehensive review navigates through latest progress in the assembly strategy and HER performance of POM-based crystal materials, alongside discussion on transition metal compounds derived from POMs, such as carbides, phosphides, and sulfides. Besides, future developments in POM-derived electrocatalyst regulation of the electrochemical HER are prospected. [ABSTRACT FROM AUTHOR]

The development of low‐cost transition metal compounds with high‐performance for efficient oxygen evolution reaction (OER) is of great significance in promoting the development of electrocatalysis. In this study, a Ce‐doped Ni3S4 catalyst (Ce0.2−Ni3S4) was synthesized through a one‐step solvothermal method, where the doped rare earth element Ce induced the transformation of NiS to Ni3S4. The Ce0.2−Ni3S4 catalyst exhibited excellent OER performance in 1 M KOH. At a current density of 10 mA cm−2, it showed a low overpotential of 230 mV and a low Tafel slope of 52.39 mV dec−1. Long‐term OER tests at the same potential lasted for 24 h without significant loss of current density. This work introduces a novel method of Ce element doping for modifying transition metal sulfides, providing new insights into the effective utilization of rare earth elements in the field of electrochemistry. It creates more chances for the progress of highly efficient catalysts for efficient OER, contributing to the advancement of electrocatalysis. [ABSTRACT FROM AUTHOR]

Developing efficient, low-cost and bifunctional catalysts with predominant durability for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is an extraordinary challenge in the preparation of green hydrogen energy by electrochemical water splitting. Three-dimensional (3D) transition metal compounds have become a research hotspot as OER electrocatalysts, which can replace noble metal oxides such as RuO 2 and IrO 2 to reduce application costs. Herein, we synthesized a novel three-dimensional pine-tree-like bimetallic sulfide arrays on nickel foam (FeCoS/NF) using various optimization strategies such as morphology optimization, in situ growth and introduction of heterogeneous structures. The as-synthesized FeCoS/NF electrocatalyst only requires relatively low overpotential of 156 mV to achieve a current density of 20 mA cm−2 for OER, with a Tafel slope of only 37 mV dec−1. It also has a small charge transfer resistance, an electrochemical surface area and good electrochemical stability in alkaline electrolytes. The excellent performance of FeCoS/NF can be attributed to the synergistic effect and amorphous phase of FeCoS as well as the well-defined pine-tree-like array architecture with a large surface area, abundant active sites, and sufficient gas and electrolyte diffusion channels. [Display omitted] • A 3D pine-tree-like structure of FeCoS/NF electrocatalyst was synthesized. • The FeCoS/NF exhibits excellent electrocatalytic activity for OER. • FeCoS/NF-based zinc-air battery shows an open-circuit voltage of 1.27 V. [ABSTRACT FROM AUTHOR]

In this work, energetic coordination compounds (ECCs) of transition metals (Fe, Ni, Cu, Zn) containing aliphatic amines as ligands were synthesized: ethylenediamine; 1,3-diaminopropane; tris(2-aminoethyl)amine; tris(3-aminopropyl)amine. The compounds were investigated in terms of ignition/explosion temperature, friction and impact sensitivity. For selected compounds, structural characterisation was presented (IR-ATR spectroscopy, Raman spectroscopy) and their morphology was determined (SEM, powder XRD). They were also investigated by differential scanning calorimetry (DSC). In order to assess the potential application of selected ECCs in detonators, underwater explosion tests were carried out, determining energetic performance. The results achieved for detonators containing ECCs were compared with those for reference detonators (containing pentaerythritol tetranitrate, PETN), indicating their potential use as a "green" alternative to nitric acid esters. [ABSTRACT FROM AUTHOR]

The rational synthesis of an electrode material with a highly active and stable architecture is very critical to achieving high-performance electrochemical energy storage. Herein, N-doped carbon restricting yolk–shell CoSe2/Ni3Se4 (CoSe2/Ni3Se4@NC) flower-like microspheres were successfully synthesized from solid CoNi-glycerate microspheres using a coating technology as an anode material for lithium-ion batteries (LIBs). The unique yolk–shell CoSe2/Ni3Se4@NC microspheres with hierarchical pores can increase the contact area with the electrolyte and provide enough transfer channels for the diffusion of Li+. The carbon layer on the surface of CoSe2/Ni3Se4@NC can not only improve the conductivity of the electrode but also provide the protective effect of active nanosheets during the process of synthesis, avoiding the overall structure collapse during the charge/discharge process of LIBs. Benefiting from the high conductivity, hollow structure, and elastic NC shell bestowed by the unique architecture, the yolk–shell CoSe2/Ni3Se4@NC anode shows excellent lithium storage performances, such as an excellent reversible specific capacity of 319 mA h g−1 at a current density of 1000 mA g−1 after 500 cycles and excellent cycling stability. This synthesis strategy provides a new way to optimize the lithium storage performance of transition metal compound electrode materials, which is helpful to the design of the next generation of high-performance LIBs. [ABSTRACT FROM AUTHOR]

The heteroatom substitution is considered as a promising strategy for boosting the redox kinetics of transition metal compounds in hybrid supercapacitors (HSCs) although the dissimilar metal identification and essential mechanism that dominate the kinetics remain unclear. It is presented that d‐p orbital hybridization between the metal and electrolyte ions can be utilized as a descriptor for understanding the redox kinetics. Herein, a series of Co, Fe and Cu heteroatoms are respectively introduced into Ni3Se4 cathodes, among them, only the moderate Co‐substituted Ni3Se4 can hold the optimal d‐p orbital hybridization resulted from the formed more unoccupied antibonding states π*. It inevitably enhances the interfacial charge transfer and ensures the balanced OH− adsorption‐desorption to accelerate the redox kinetics validated by the lowest reaction barrier (0.59 eV, matching well with the theoretical calculations). Coupling with the lower OH− diffusion energy barrier, the prepared cathode delivers ultrahigh rate capability (~68.7 % capacity retention even the current density increases by 200 times), and an assembled HSC also presents high energy/power density. This work establishes the principles for determining heteroatoms and deciphers the underlying effects of the heteroatom substitution on improving redox kinetics and the rate performance of battery‐type electrodes from a novel perspective of orbital‐scale manipulation. [ABSTRACT FROM AUTHOR]

We report herein a versatile method for synthesis of nickel-based inorganic compounds (i.e., Ni–O, Ni–S, Ni–Se, and Ni–P) from one basic nickel-cyanide-bridged coordination polymer (Ni-CP) flakes via a straightforward one-step annealing operation. Thus obtained Ni-based cocatalysts have been loaded over TiO 2 via facile incipient impregnation method to investigate performance towards H 2 production via H 2 O splitting reaction. Among examined compounds, the optimized 0.5Ni-P@TiO 2 exhibited the best photocatalytic activity with a hydrogen generation rate of 7.32 mmol h−1 g−1 compared with pristine TiO 2 (0.086 mmol h−1 g−1). While the 4Ni–Se@TiO 2 has revealed the strongest durability with cumulative hydrogen amount of 48.6 mmol g−1 upon a 5-h reaction, which is 81-fold higher than TiO 2 at identical conditions. On the other hand, Ni–S, Ni–P, and Ni–O, impregnated with 0.5 wt% of titania, show 13, 46, and 49-fold enhancement in evolved H 2 amount higher than the bare titanium dioxide. Additionally, the mixtures have been investigated again through photo-electrochemical measurements confirming the outperforming performance of Ni–P@TiO 2 (0.5% wt). The processed synthesis methodology is economical and easy opening a door to synthesizing various transition metal compound/semiconductor composites for efficient water photocatalytic hydrogen generation. [Display omitted] • Hydrogen extracted from water considered as a future fuel because of its sustainability and cleanliness. • The problem of huge energy required to split H–OH bond in water can be overcome through. • Among several approaches to produce green hydrogen from water, photocatalysis is the completely sustainable and eco-friendly approach. • Herein, we synthesized four nickel compounds from one parent Ni-CP, and investigated their influence on titania photocatalytic properties via water-splitting reaction. • 0.5Ni-P@TiO 2 composite provided the highest HGR (7.3 mmol h−1 g−1) with excellent electrical characteristics, while 4Ni–Se@TiO 2 composite gave the highest cumulative H 2 amount (48.6 mmol g−1), which indicated its distinguished stability. [ABSTRACT FROM AUTHOR]

Herein, we have successfully fabricated a novel SnO2/MoS2heterostructure catalyst that exhibits exceptional activity and selectivity in the eNRR process.Unlike conventional heterogeneous structures, our heterostructure design deliberately incorporates an n -type semiconductor (SnO2) and a p-type semiconductor (MoS2) to induce an electric field at the interfaces. Through comprehensive theoretical and experimental investigations, we have not only confirmed the successful construction of the interfacial electric field but have also uncovered its profound impact on eNRR. Our findings reveal multiple crucial roles played by the interfacial electric field effect in eNRR catalysis. Firstly, it facilitates rapid electron transfer during the eNRR process, leading to accelerated reaction kinetics. Additionally, it promotes efficient N2adsorption and N N bond activation, thereby reducing the energy barrier of the rate-determining step. [Display omitted] Electrochemical nitrogen reduction (eNRR) is a cost-effective and environmentally sustainable approach for ammonia production. MoS 2 , as a typical layered transition metal compound, holds significant potential as an electrocatalyst for the eNRR. Nevertheless, it suffers from a limited number of active sites and low electron transfer efficiency. In this study, we constructed a heterostructure by depositing SnO 2 (an n -type semiconductor) nanoparticles on MoS 2 (a p-type semiconductor). This unique interfacial structure not only generates abundant interfacial contacts but also facilitates the transfer of electrons from SnO 2 to MoS 2 , leading to the formation of an interfacial electric field. Theoretical calculations demonstrate that this electric field increases the number of active electrons, facilitating N 2 adsorption and N N bond activation. Moreover, it increases the degree of orbital overlap between N 2 and SnO 2 /MoS 2 , effectively reducing the energy barrier of the rate-determining step. Benefiting from the interfacial electric field effect, the SnO 2 /MoS 2 catalyst exhibits significant catalytic activity and selectivity towards eNRR, with an ammonia yield of 47.1 µg h−1 mg−1 and a Faraday efficiency of 19.3 %, surpassing those reported for the majority of MoS 2 - and SnO 2 -based catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] Compared with layered materials such as graphite and transition metal disulfide compounds with highly anisotropic in-plane covalent bonds, it is inherently more challenging to obtain independent metallic two-dimensional films with atomic thickness. In this study, PtNi layered metallene nanobowls (LMBs) with multilayer atomic-scale nanosheets and bowl-like structures have been synthesized in one step using structural and electronic effects. The material has the advantage of catalyzing pH-universal hydrogen evolution reaction (HER). Compared with Pt/C, PtNi LMBs exhibited excellent HER activity and stability under all pH conditions. The overpotentials of 10 mA cm−2 at 0.5 M H 2 SO 4 , 1.0 M phosphate buffer and 1.0 M KOH were 14.8, 20.3, and 34.0 mV, respectively. Under acidic, neutral and alkaline conditions, the HER Faraday efficiencies reach 98.97%, 98.85%, and 99.04%, respectively. This study provides an example for the preparation of unique multilayer nanobowls, and also provides a basic research platform for the development of special HER materials. [ABSTRACT FROM AUTHOR]

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Four polyoxomolybdated compounds based on Tetp (Tetp = 4-[4-(2-Thiophen-2-yl-ethyl)-4H-[1, 2, 4]triazole-3-yl]-pyridine), namely [Zn(Tetp)2(H2O)2][(β-Mo8O26)0.5] (Zn-Mo8), [Co(Tetp)2(H2O)2][(β-Mo8O26)0.5] (Co-Mo8), [Cu4(Tetp)6(H2O)2]{H3[K(H2O)3](θ-Mo8O26)(Mo12O40)}·8H2O (Cu-Mo20) and [Cu3(Tetp)3][PMo12O40]·H2O (Cu-PMo12) are synthesized by hydrothermal methods and are used as electrode materials for supercapacitors(SCs) and electrochemical sensors. Inserting polyoxometalates (POMs) with redox active sites into transition metal compounds (TMCs) can improve the internal ion/electron transfer rate, thus effectively enhancing the electrochemical performance. Compared with the parent POMs, four compounds exhibit excellent electrochemical properties. In particular, Cu-PMo12 shows an excellent specific capacitance (812.3 F g−1 at 1 A g−1) and stability (94.42%), as well as a wide detection range (0.05 to 1250 µM) and a low detection limit (0.057 µM) for NO2- sensing. [ABSTRACT FROM AUTHOR]

The luminescent properties of Au(I) and Pt(II) compounds are commonly tuned by exploiting the alkynyl ligand with varying electron density. Herein, we describe the synthesis of three new emissive transition metal compounds, tbpyPt(C2pym)2, Ph3PAuC2pym, and Cy3PAuC2pym (where HC2pym = 2-ethynylpyrimidine), verified by 1H-NMR, EA, and a single-crystal X-ray diffraction analysis. The tbpyPt(C2pym)2 complex crystallized as an Et2O solvate in the orthorhombic space group Pbca with Z = 24 with three unique Pt(II) species within the unit cell. The Cy3PAuC2pym species crystallizes in a monoclinic space group with one unique complex in the asymmetric unit. Changing the identity of the phosphine from Cy3P to Ph3P influences interactions within the unit cell. Ph3PAuC2pym, which also crystalizes in a monoclinic space group, has an aurophilic bonding interaction Au–Au distance of 3.0722(2) Å, which is not present in crystalline Cy3PAuC2pym. Regarding optical properties, the use of an electron-deficient heterocycle provides an alternate approach to blue-shifting the emission of Pt(II) transition metals' compounds, where the aryl moiety is made more electron-deficient by exploiting nitrogen within this moiety instead of the typical strategy of decorating the aryl ring with electron withdrawing substituents (e.g., fluorines). This is indicated by the blue-shift in emission that occurs in tbpyPt(C2pym)2 (λmax, emission = 512 nm) compared to the previously reported tbpyPt(C22-py)2 (where HC22-py = 2-ethynylpyridine) complex (λmax, emission = 520 nm). [ABSTRACT FROM AUTHOR]

Recently, Kohn–Sham (KS) methods with new correlation functionals, called σ-functionals, have been introduced. Technically, σ-functionals are closely related to the well-known random phase approximation (RPA); formally, σ-functionals are rooted in perturbation theory along the adiabatic connection. If employed in a post-self-consistent field manner in a Gaussian basis set framework, then, σ-functional methods are computationally very efficient. Moreover, for main group chemistry, σ-functionals are highly accurate and can compete with high-level wave-function methods. For reaction and transition state energies, e.g., chemical accuracy of 1 kcal/mol is reached. Here, we show how to calculate first derivatives of the total energy with respect to nuclear coordinates for methods using σ-functionals and then carry out geometry optimizations for test sets of main group molecules, transition metal compounds, and non-covalently bonded systems. For main group molecules, we additionally calculate vibrational frequencies. σ-Functional methods are found to yield very accurate geometries and vibrational frequencies for main group molecules superior not only to those from conventional KS methods but also to those from RPA methods. For geometries of transition metal compounds, not surprisingly, best geometries are found for RPA methods, while σ-functional methods yield somewhat less good results. This is attributed to the fact that in the optimization of σ-functionals, transition metal compounds could not be represented well due to the lack of reliable reference data. For non-covalently bonded systems, σ-functionals yield geometries of the same quality as the RPA or as conventional KS schemes combined with dispersion corrections. [ABSTRACT FROM AUTHOR]

Transition metal compounds with kagome structure have been found to exhibit a variety of exotic structural, electronic, and magnetic orders. These orders are competing with energies very close to each other, resulting in complex phase transitions. Some of the phases are easily observable, such as the charge density wave (CDW) and the superconducting phase, while others are more challenging to identify and characterize. Here we present magneto-transport evidence of a new phase below ~ 35 K in the kagome topological metal CsV3Sb5 (CVS) thin flakes between the CDW and the superconducting transition temperatures. This phase is characterized by six-fold rotational symmetry in the in-plane magnetoresistance (MR) and is connected to the orbital current order in CVS. Furthermore, the phase is characterized by a large in-plane negative magnetoresistance, which suggests the existence of a three-dimensional, magnetic field-tunable orbital current ordered phase. Our results highlight the potential of magneto-transport to reveal the interactions between exotic quantum states of matter and to uncover the symmetry of such hidden phases. Recent studies reported evidence of a new phase in the kagome metal CsV3Sb5 between the charge density wave and superconducting transitions. Here the authors reveal symmetry properties of this phase in CsV3Sb5 thin flakes probed by in-plane magnetotransport, suggesting a 3D orbital current order. [ABSTRACT FROM AUTHOR]

A 2×2×1 superstructure of the P63/mmc NiAs structure is reported in which kagome nets are stabilized in the octahedral transition metal layers of the compounds Ni0.7Pd0.2Bi, Ni0.6Pt0.4Bi, and Mn0.99Pd0.01Bi. The ordered vacancies that yield the true hexagonal kagome motif lead to filling of trigonal bipyramidal interstitial sites with the transition metal in this family of "kagome‐NiAs" type materials. Further ordering of vacancies within these interstitial layers can be compositionally driven to simultaneously yield kagome‐connected layers and a net polarization along the c axes in Ni0.9Bi and Ni0.79Pd0.08Bi, which adopt Fmm2 symmetry. The polar and non‐polar materials exhibit different electronic transport behaviour, reflecting the tuneability of both structure and properties within the NiAs‐type bismuthide materials family. [ABSTRACT FROM AUTHOR]

A series of transition metal‐pnictogenide compounds were prepared starting from [(Dipp2NacNac)MCl] (M=Cr, Mn, Fe, Zn) (Dipp2NacNac=HC{C(Me)N(Dipp)}2) and [M'E(SiMe3)2] (M'=Li, K; E=P, As, Sb) as well as [Li(Et2O)nPH2] and [Li(tmeda)AsH2]. In the course of these investigations we were able to characterize all permutations for compounds of the composition [(Dipp2NacNac)ZnE(SiMe3)2] (E=P, As, Sb) and [(Dipp2NacNac)ZnEH2] (E=P, As). Moreover, the synthesis of selected compounds of type [(Dipp2NacNac)ME(SiMe3)2] for M=Cr, Mn, Fe and E=P−Sb are described. As part of our efforts, we established a number of bonding motifs that are underexplored in the literature to date. All isolated compounds, were examined by NMR spectroscopy, IR spectroscopy, Elemental analysis and X‐Ray structure analysis. DFT calculations on the chromium compounds were performed to investigate the binding situation between chromium and the group 15 element in more detail. [ABSTRACT FROM AUTHOR]

Along with great attention to eco-friendly power solutions, sodium ion batteries (SIBs) have stepped into the limelight for electrical vehicles (EVs) and grid-scale energy storage systems (ESSs). SIBs have been perceived as a bright substitute for lithium ion batteries (LIBs) due to abundance on Earth along with the cost-effectiveness of Na resources compared to Li counterparts. Nevertheless, there are still inherent challenges to commercialize SIBs due to the relatively larger ionic radius and sluggish kinetics of Na+ ions than those of Li+ ions. Particularly, exploring novel anode materials is necessary because the conventional graphite anode in LIBs is less active in Na cells and hard carbon anodes exhibit a poor rate capability. Various metal compounds have been examined for high-performance anode materials in SIBs and they exhibit different electrochemical performances depending on their compositions. In this review, we summarize and discuss the correlation between cation and anion compositions of metal compound anodes and their structural features, energy storage mechanisms, working potentials, and electrochemical performances. On top of that, we also present current research progress and numerous strategies for achieving high energy density, power, and excellent cycle stability in anode materials. [ABSTRACT FROM AUTHOR]

The photo-enhanced electrocatalytic method of oxygen evolution reaction (OER) shows promise for enhancing the effectiveness of clear energy generation through water splitting by using renewable and sustainable source of energy. However, despite benefits of photoelectrocatalytic (PEC) water splitting, its uses are constrained by its low efficiency as a result of charge carrier recombination, a large overpotential, and sluggish reaction kinetics. Here, we illustrate that Nickel telluride (NiTe) synthesized by hydrothermal methods can function as an extremely effective photo-coupled electrochemical oxygen evolution reaction (POER) catalyst. In this study, NiTe was synthesized by hydrothermal method at 145°C within just an hour of reaction time. In dark conditions, the NiTe deposited on carbon cloth substrate shows a small oxygen evolution reaction overpotential (261 mV) at a current density of 10 mA cm-2, a reduced Tafel slope (65.4 mV dec-1), and negligible activity decay after 12 h of chronoamperometry. By virtue of its enhanced photo response, excellent light harvesting ability, and increased interfacial kinetics of charge separation, the NiTe electrode under simulated solar illumination displays exceptional photoelectrochemical performance exhibiting overpotential of 165 mV at current density of 10 mA cm-2, which is about 96 mV less than on dark conditions. In addition, Density Functional Theory investigations have been carried out on the NiTe surface, the results of which demonstrated a greater adsorption energy for intermediate -OH on the catalyst site. Since the -OH adsorption on the catalyst site correlates to catalyst activation, it indicates the facile electrocatalytic activity of NiTe owing to favorable catalyst activation. DFT calculations also revealed the facile charge density redistribution following intermediate -OH adsorption on the NiTe surface. This work demonstrates that arrays of NiTe elongated nanostructure are a promising option for both electrochemical and photoelectrocatalytic water oxidation and offers broad suggestions for developing effective PEC devices. [ABSTRACT FROM AUTHOR]

This paper briefly discusses electronegativity and uses of the electronegativity scale. It demonstrates that values of electronegativity can be used quantitatively in simple equations. Formulas containing derived values of elemental electronegativities are shown to calculate dipole moments, bond lengths, and bond energies reliably. Comparison between calculated and experimental values shows very good agreement in the vast majority of cases. [ABSTRACT FROM AUTHOR]

Recently main group compounds have stepped into the territory of precious transition metal compounds with respect to utility in the homogeneous catalysis of fundamentally important organic transformations. Inspired by the need to promote more sustainability in chemistry because of their greater abundance in nature, this change of direction is surprising since main group metals generally do not possess the same breadth of reactivity as precious transition metals. Here, we introduce the dihydropyridylsodium compound, Na-1,2-tBu-DH(DMAP), and its monomeric variant [Na-1,2-tBu-DH(DMAP)]·Me6TREN, and demonstrate their effectiveness in transfer hydrogenation catalysis of the representative alkene 1,1-diphenylethylene to the alkane 1,1-diphenylethane using 1,4-cyclohexadiene as hydrogen source [DMAP = 4-dimethylaminopyridine; Me6TREN = tris(N,N-dimethyl-2-aminoethyl)amine]. Sodium is appealing because of its high abundance in the earth's crust and oceans, but organosodium compounds have been rarely used in homogeneous catalysis. The success of the dihydropyridylsodium compounds can be attributed to their high solubility and reactivity in organic solvents. Organosodium compounds are appealing sustainable alternatives to precious transition metal compounds, yet they have rarely been used in homogeneous catalysis. Here, the authors introduce a dihydropyridylsodium compound, Na1,2-tBu-DH(DMAP), and its monomeric variant [Na-1,2-tBuDH(DMAP)]·Me6TREN, and demonstrate their effectiveness in transfer hydrogenation catalysis of a representative alkene, 1,1-diphenylethylene, using 1,4-cyclohexadiene as a hydrogen source. [ABSTRACT FROM AUTHOR]

Nanocrystalline Cu2Cu1−xFexSnS4 (CCFTS) was prepared by a simple liquid-phase method. Physiochemical properties of the CCFTS powder as well as the CEs fabricated thereby were investigated using XRD, Raman spectroscopy, SEM, UV–Vis absorption, electrochemical impedance spectroscopy (EIS), etc. Conduction band shifts as well as the bandgap increases in the as-prepared CCFTS as a function of the Fe content were observed. For the dye-sensitized solar cells (DSSCs) with CCFTS counter electrodes (CEs), charge transfer impedance (Rct1) and short-circuit current (Jsc) were reduced by 64.54% and improved by 14.64%, respectively, compared with that with Fe-free Cu3SnS4 (CTS) CE. The enhancement of electron transfer through the CE/electrolyte interfaces stems from the optimal energy level alignment and the surface morphology tuned by the Fe alloying and hence improve the electrocatalytic activity of the CEs for the reduction from I3− to I−. As a consequence, photovoltaic conversion efficiency (PCE) of 6.95% was obtained which is 1.25 times that of the cell with Fe-free CTS CE. This work confirmed that element alloying into nanocrystalline transition metal compounds is effective for catalytic activity improvement. Material preparation reported herein is feasible, has high efficiency and low cost, and believed beneficial to high DSSCs development. [ABSTRACT FROM AUTHOR]

Transition metals and their oxide compounds exhibit excellent chemical reactivity; however, their easy agglomeration and high cost limit their catalysis applications. In this study, an interpolation structure of a Myriophyllum verticillatum L. biochar-supported Mn/Mg composite (Mn/Mg@MV) was prepared to degrade triphenyl phosphate (TPhP) from wastewater through the activating periodate (PI) process. Interestingly, the Mn/Mg@MV composite showed strong radical self-producing capacities. The Mn/Mg@MV system degraded 93.34% TPhP (pH 5, 10 μM) within 150 min. The experimental results confirmed that the predominant role of IO3· and the auxiliary ·OH jointly contributed to the TPhP degradation. In addition, the TPhP pollutants were degraded to various intermediates and subsequent Mg mineral phase mineralization via mechanisms like interfacial processes and radical oxidation. DFT theoretical calculations further indicated that the synergy between Mn and Mg induced the charge transfer of the carbon-based surface, leading to the formation of an ·OH radical-enriched surface and enhancing the multivariate interface process of ·OH, IO3, and Mn(VII) to TPhP degradation, resulting in the further formation of Mg PO4 mineralization. [ABSTRACT FROM AUTHOR]

Biomedical assays based on optical nanoprobes play an important role in human health. Optical nanoprobes, the nanomaterials with special optical properties, are widely utilized in biomedical assays. Compared with traditional materials, the well-performed optical nanoprobes have certain properties, such as negligible interferences from the background fluorescence and scattering, simple operations and instruments, high sensitivity, and excellent specificity. This paper reviews the mechanisms, materials, and applications of optical nanoprobes. The mechanisms of optical nanoprobes involve fluorescence, phosphorescence, Forster resonance energy transfer (FRET), upconversion luminescence and chemiluminescence. Time-resolved luminescent nanoprobes are usually prepared from rare earth compounds and quantum dots (QDs). Ultralong inorganic phosphorescent nanoprobes are prepared from transition metal compounds, while ultralong organic phosphorescent nanoprobes are usually prepared from π-conjugated compound nanocrystals that exhibit a rigid confinement to suppress the non-radiative transitions and contain heavy atoms to enhance ISC. Time-resolved luminescent nanoprobes and ultralong phosphorescent nanoprobes minimize background interferences by longer luminescence lifetime. Chemiluminescent nanoprobes are usually prepared from compounds that can react with reactive oxygen species (ROS) to form peroxide bonds. Upconversion luminescent nanoprobes are usually prepared from inorganic rare earth fluoride nanocrystals. Chemiluminescent nanoprobes and upconversion luminescent nanoprobes can avoid background interferences because excitation light of shorter wavelength is not needed. FRET nanoprobes and luminescence quenching nanoprobes are prepared from a donor and an acceptor that can be linked or delinked by the analyte. Optical nanoprobes are applied in both in vitro diagnoses and in vivo imaging. The in vitro applications of optical nanoprobes include the determination of varieties of biomacromolecules and small molecules, while the in vivo imaging involves the diagnoses of inflammation and tumors. [ABSTRACT FROM AUTHOR]

In this work, we report on a comparative study of the structural, optical, and elastic properties of SrTiSe3 and SrZrSe3 compounds using the DFT method. The lattice constants of the compounds are calculated using the GGA-PBE approximation and the hybrid functional Heyd, Scuseria, and Ernzerhof (HSE). The properties of the SrTiSe3 and SrZrSe3 materials in relation to electronic composition, elastic constants, and optical characteristics are deduced and analyzed. Both compounds display magnetic behavior, according to electronic calculations. SrTiSe3 shows metallic behavior, as the calculated bandgap value is zero. SrZrSe3, on the other hand, has a bandgap of 0.347 eV, which demonstrates its semiconducting nature. We have demonstrated that the plasma frequency of SrTiSe3 is around 1.77836. Using density functional theory, we report on the electronic characteristics of the compounds under mechanical stress. For SrZrSe3, the gap energy values rise with compressive stress and decrease with increasing tensile stress to zero. In addition, the study includes the extinction coefficient, optical conductivity, dielectric tensor, electron energy loss, and refractive index. [ABSTRACT FROM AUTHOR]

We explore new transition metal (TM) compound sub-nanoclusters, TM8X6 (TM = Mn, Fe, Co and X = P, B, As), using density functional theory. Their optimized geometric structures show the same polyhedral structure (tetrahexahedron) independent of a kind of TM and metalloid (X), where eight TM atoms form a cubic structure capped with six metalloid (X) atoms. Incorporating an extra TM atom into the TM cubic results in an endohedral structure, TM9X6. Encapsulation of an additional TM atom merely changes the binding energy except for the Co boride cluster. The binding energy of Co8B6 increases by incorporating an additional Co atom, in which it is observed that the electron density is accumulated between B and all Co atoms (Co atoms both at the center and at the edges), but in other clusters, the electron excess is found mainly between TM atoms. The MnnP6 (n = 8 and 9) clusters have a high adiabatic electron affinity (>6 eV) due to the relatively large difference in electronegativity between Mn and P. The highest occupied molecular orbital and lowest unoccupied molecular orbital gaps of all clusters lie in the visible range. The interaction between nanoclusters and graphene with a single vacancy is studied as a function of the different cluster landing site on the graphene, where the geometric structure change of the clusters strongly depends on the adsorption site. [ABSTRACT FROM AUTHOR]

This review presents a comprehensive overview of the special strategies employed to boost the electrochemical performances of TMBs in Li-S batteries. [Display omitted] Although the lithium-sulfur (Li-S) battery has a theoretical capacity of up to 1675 mA h g−1, its practical application is limited owing to some problems, such as the shuttle effect of soluble lithium polysulfides (LiPSs) and the growth of Li dendrites. It has been verified that some transition metal compounds exhibit strong polarity, good chemical adsorption and high electrocatalytic activities, which are beneficial for the rapid conversion of intermediate product in order to effectively inhibit the "shuttle effect". Remarkably, being different from other metal compounds, it is a significant characteristic that both metal and boron atoms of transition metal borides (TMBs) can bind to LiPSs, which have shown great potential in recent years. Here, for the first time, almost all existing studies on TMBs employed in Li-S cells are comprehensively summarized. We firstly clarify special structures and electronic features of metal borides to show their great potential, and then existing strategies to improve the electrochemical properties of TMBs are summarized and discussed in the focus sections, such as carbon-matrix construction, morphology control, heteroatomic doping, heterostructure formation, phase engineering, preparation techniques. Finally, the remaining challenges and perspectives are proposed to point out a direction for realizing high-energy and long-life Li-S batteries. [ABSTRACT FROM AUTHOR]

The N-oxide functional group has been exploited for synthetic strategies and drug design, and it has been utilized in imaging agents. Herein, we present rare examples of neutral heteroleptic cyclometallated Ir(III) compounds that contain an uncoordinated N-oxide functional group. These species, along with others described within, were verified by NMR, EA, HRMS, and single-crystal X-ray analysis. N-oxide-containing Ir(III) species were prepared selectively in high yields > 66% from chloro-bridged Ir(III) dimers with Acipimox, a picolinate-type ligand containing the N-oxide functional group. Non-N-oxide analogs were synthesized in a similar fashion (yields > 77%). Electrochemical comparison (cyclic voltammetry) indicates that the presence of an N-oxide functional group anodically shifts the reduction potential, suggesting that the N-oxide is acting as an electron-withdrawing group in these species. Crystallographic studies were pursued to examine the coordination behavior of these N-oxides compared to their non-oxidized congeners. The Ir(III) complexes with Acipimox indeed leave the N-oxide uncoordinated and exposed on the complexes. The uncoordinated N-oxide group is influential in directing the packing structures of these complexes directly through C-H···O and O···π interactions at the N-oxide. The crystallographic characterization of cationic Ir(III) compounds with uncoordinated nitrogen atoms is also presented. The C-H···N interactions between these complexes form a variety of dimers, finite chains, and continuous chains. Future work will focus on functionalizing the cationic Ir(III) species into their corresponding N-oxide derivatives and rigorously characterizing how the N-oxide functional group impacts the optical properties of transition metal compounds in both cationic and neutral complexes. [ABSTRACT FROM AUTHOR]

Six different polyoxotungstate-based transition metal complexes were synthesized, namely [Cu5(2,2′-bpy)5(μ2-Cl)2(PO4)2(H2O)2][HPW12O40]·2H2O (1), [Cu1.5(2,2′-bpy)1.5(inic)2(H2O)1.5]3[H1.5PW12O40]2·16.25H2O (2), [Cu(2,2′-bpy)2]2[SiW12O40]·10H2O (3), [Zn(phen)3]2[PWVW VI11 O40]·5H2O (4), [Zn(phen)2(H2O)]2[SiW12O40]·2H2O (5), and [Zn(2,2′-bpy)2]2[SiW12O40] (6) (2,2′-bpy = 2,2′-bipyridine, inic = isonicotinic acid, phen = 1,10-phenanthroline). Compound 1 is based on [HPW12O40]2− anions, which are accommodated within the open channels of a supramolecular network formed by novel Cu–P–Cl coordination clusters. Compound 2 is constructed from [H1.5PW12O40]1.5− and novel [Cu1.5(2,2′-bpy)1.5(inic)2(H2O)1.5]+ coordination fragments, and polyoxoanions are encapsulated within the pores created by the copper coordination fragments, resulting in a unique three-dimensional supramolecular architecture. Compound 3 is a two-dimensional structure formed through the covalent linkage between [SiW12O40]4− and [Cu(2,2′-bpy)2]2+. Compound 4 is a supramolecular architecture formed by [PWVW VI11 O40]4− and [Zn(phen)3]2+ coordination fragments, while compound 5 is a supramolecular structure based on POM bi-supported Zn coordination complexes. Compound 6 is a two-dimensional framework structure constituted by [SiW12O40]4− and [Zn(2,2′-bpy)2]2+via covalent interactions. In addition, electrochemical measurement results show that the copper-based tungstate compounds 1–3 and zinc-based tungstate compounds 4–6 exhibit different performances and durabilities as electrochemical capacitors (compound 1 shows the highest specific capacitance of 94.0 F g−1 at 1.5 A g−1, whereas compound 6 maintains the best cycling stability with the capacity retention of 80.7% after 1000 cycles at 4 A g−1.). This study contributes to the development of POM-based transition metal complexes with high capacitance by providing insights into the design and synthesis process. [ABSTRACT FROM AUTHOR]