Selenium Sites Research Articles

Mechanism of Defect Passivation in Sb2Se3 Solar Cells via Buried Selenium Seed Layer

AbstractQuasi‐1D antimony selenide (Sb2Se3) is known for its stable phase structure and excellent light absorption coefficient, making it a promising material for high‐efficiency light harvesting. However, the (Sb4Se6)n ribbons align horizontally, increasing defect interference and limiting vertical carrier transport. Herein, a novel strategy of burying selenium (Se) seed layers to reduce lattice mismatch at the heterojunction interface, promote crystal orientation, mitigate deep donor defects, increase P‐type carrier concentration, and purify the PN junction, is proposed. Admittance spectroscopy reveals that Sb2Se3 solar cells with Se seed layers have higher activation energies for defect states and significantly lower defect densities (1.2 × 1014, 2.7 × 1014, and 1.3 × 1015 cm−3 for D1, D2, and D3) compared to an order of magnitude higher densities in Sb2Se3 solar cells without a Se seed layer. First‐principles calculations support these findings, showing that Se seed layers create a Se‐rich environment, reducing selenium vacancies (VSe), antimony on selenium sites (SbSe), and interface defects. This dual passivation mechanism suppresses defect formation and activation, increasing carrier concentration and open‐circuit voltage (VOC). Ultimately, employing this novel method, a VOC of 498.3 mV and an efficiency of 8.42%, the highest performance reported for Sb2Se3 solar cells prepared via vapor transport deposition (VTD), are achieved.

Bimetallic sulfides CuInSe2 adsorbent for rapid elemental mercury uptake from coal-fired flue gas

Abstract Coal-fired power plants use coal as fuel, which will release a lot of mercury in the combustion process, directly threatening the ecological environment of the earth. In this study, a new adsorbent CuInSe2 with an active selenium site was prepared, which can effectively remove Hg0. The flower structure of the adsorbent with uniform distribution of selenium sites was confirmed by SEM characterization. Experimental results demonstrated that the adsorption efficiency was close to 99% at 80 ∼200°C, and the adsorption efficiency remained at a stable level of 92.39% even after continuous exposure for 6 hours. The equilibrium adsorption capacity was 18.64 mg/g. CuInSe2 has excellent resistance to SO2 and NO. In conclusion, CuInSe2 adsorbents possess significant potential for mercury removal, providing a new direction for the remediation of mercury pollution in various industrial waste gases using dual-metal selenide adsorbents.

Metal-Bound Sulfur and Selenium Sites as Halogen Bond Acceptors: The Supramolecular Association of Rhodium(I) Half-Lantern Complexes with 1,4-Diiodotetrafluorobenzene

Metal-Bound Sulfur and Selenium Sites as Halogen Bond Acceptors: The Supramolecular Association of Rhodium(I) Half-Lantern Complexes with 1,4-Diiodotetrafluorobenzene

Biomimetic mercury immobilization by selenium functionalized polyphenylene sulfide fabric

Highly efficient decontamination of elemental mercury (Hg0) remains an enormous challenge for public health and ecosystem protection. The artificial conversion of Hg0 into mercury chalcogenides could achieve Hg0 detoxification and close the global mercury cycle. Herein, taking inspiration from the bio-detoxification of mercury, in which selenium preferentially converts mercury from sulfoproteins to HgSe, we propose a biomimetic approach to enhance the conversion of Hg0 into mercury chalcogenides. In this proof-of-concept design, we use sulfur-rich polyphenylene sulfide (PPS) as the Hg0 transporter. The relatively stable, sulfur-linked aromatic rings result in weak adsorption of Hg0 on the PPS rather than the formation of metastable HgS. The weakly adsorbed mercury subsequently migrates to the adjacent selenium sites for permanent immobilization. The sulfur-selenium pair affords an unprecedented Hg0 adsorption capacity and uptake rate of 1621.9 mg g−1 and 1005.6 μg g−1 min−1, respectively, which are the highest recorded values among various benchmark materials. This work presents an intriguing concept for preparing Hg0 adsorbents and could pave the way for the biomimetic remediation of diverse pollutants.

Hit two birds with one stone: A bi-functional selenium-substituted organosulfur polymer additive for high-performance lithium-sulfur batteries

Sluggish reaction kinetics of sulfur cathode and high reactivity of lithium anode hinder the commercialization of Li-S batteries. Employing the electrolyte additive to regulate the states of active material is a facile and effective way to solve the above issues. Herein, the bifunctional selenium substituted lithium polythioctic acid (PTA-Se) was prepared as an additive of electrolyte via in-situ polymerization and substitution method. Such additives can promote the conversion of polysulfides and facilitate the homogenization of Li-ion flux. The active selenium sites provide a kinetically favorable pathway for polysulfide conversion. The introduction of additives also facilitates the formation of elastic and uniform solid electrolyte phase interface (SEI) film on the surface of lithium anode. As results, Li-S batteries assembled with PTA-Se additive demonstrates a high initial capacity of 1319 mAh g−1 at 0.2C with 1000 mAh g−1 remaining after 150 cycles, corresponding to a 0.16 % capacity decay per cycle. At a high rate of 5C, the cell still achieves a reversible capacity of 517 mAh g−1. This work opens a new avenue for designing effective electrolyte additive and achieving high-performance Li-S batteries.

Non-bonding modulations between single atomic cerium and monodispersed selenium sites towards efficient oxygen reduction

Non-bonding modulations between single atomic cerium and monodispersed selenium sites towards efficient oxygen reduction

Trigger selenium sites and stable multiphasic-engineered modulated BiFeO3/MoSe2-1T/2H photocatalyst for hydrogen peroxide production

Regulating electron density at active sites holds profound importance in the advancement of highly efficient photocatalysts for hydrogen peroxide (H2O2) production. In this study, a novel and stable multiphasic BiFeO3/MoSe2-1 T/2 H (BFO/MSe) catalyst with selenium (Se) sites, was successfully synthesized. This catalyst exhibited distinctive multiphasic structures and an abundance of active sites, showcasing unexpectedly high activity and stability within photocatalytic systems. Notably, the optimized 4BFO/MSe demonstrated an outstanding catalytic rate for H2O2 production (1640 μmol•g−1•h−1). The spontaneously generated internal electric field facilitated charge transport, which enhanced the photocatalytic property. Moreover, the characteristics of multiphasic structures further facilitated efficient charge transfer and conduction, providing active sites. Furthermore, the electron-deficient Se sites (Seδ+) within the BFO/MSe catalysts accelerated the redox cycling of transition metals, thereby accelerating the production of reactive oxygen species. By employing multiphasic engineering and Se sites, the potential applications of catalysts in H2O2 production can be effectively broadened.

The Effects of Chlorine Doping on the Thermoelectric Properties of Bi2O2Se

In this study, we investigate the effects of chlorine doping on the structural, electronic, and thermoelectric properties of Bi2O2Se by employing density functional theory combined with semiclassical Boltzmann transport theory. It is shown that chlorine doping has significant effects on the electronic structure and thermoelectric properties of Bi2O2Se. As chlorine is incorporated into the selenium sites in Bi2O2Se, additional electrons are acquired, thereby inducing metallic properties in chlorine-doped Bi2O2Se. Meanwhile, Cl doping leads to an increase in the electrical conductivity of Bi2O2Se at room temperature by 25 times (from 358.59 S/cm to 9390 S/cm), and the power factor is enhanced by a factor of 2.12 (from 4.04 mW/mK2 to 12.59 mW/mK2). This study demonstrates that chlorine doping is an effective method to modify the physical properties of Bi2O2Se.

Effect of alloying in monolayer niobium dichalcogenide superconductors

When sulfur and silicon are incorporated in monolayer 2H-NbSe2 the superconducting transition temperature, Tc, has been found to vary non-monotonically. This was assumed to be a manifestation of fractal superconductivity. Using first-principles calculations, we show that the nonmonotonic dependence of Tc is insufficient evidence for multifractality. A unifying aspect in our study are selenium vacancies in NbSe2, which are magnetic pair-breaking defects that we propose can be present in considerable concentrations in as-grown NbSe2. We show that sulfur and silicon can occupy the selenium sites and reduce the pair-breaking effect. Furthermore, when sulfur is incorporated in NbSe2, the density of states at the Fermi level and the proximity to magnetism in the alloy are both reduced compared to the parent compound. Based on our results, we propose an alternative explanation of the non-monotonic change in Tc which does not require the conjecture of multifractality.

Binding and energetics of oxygen at the CuInSe2 chalcopyrite and the CuInSe2/CdS interface

The introduction of oxygen in thin-film solar cells based on the CuInSe2 compound and related CuInSe2/CdS devices has been known to affect their electrical properties, with a tendency of neutralizing part of the donor density and favoring a p-type behavior for the CuInSe2 (CIS) absorber material. The present study employed calculations based on density-functional theory supplemented with a hybrid-functional approach to determine the energetics of oxygen incorporation in the bulk CIS compound and the CIS/CdS heterojunction interface. The latter was represented by two distinct faceted interface variants. Oxygen atoms were assumed to exist both as interstitial and substitutional impurities, in the latter case occupying vacant selenium sites. The calculations identified the structural relaxation patterns and examined the thermodynamic stability of the impurity as a function of the electron and the elemental chemical potentials. Oxygen was found to incorporate favourably at the core of the CIS/CdS interfaces, in most cases by taking up a bridging position within the nearest In–In pair. The sites of the lowest-energy oxygen configurations were found to be associated with a copper-poor local environment, owing to the presence of copper vacancies or the relaxation-induced breaking of a copper-oxygen bond. The electronic structures of the CIS/CdS interfaces were also studied by analyzing the site-projected and layer-resolved densities of states for several layers within the interfacial cores. Oxygen introduced deep-lying nonbonding levels and impurity-host bonding states in the valence-energy region.

77Se-13C based dipolar correlation experiments to map selenium sites in microcrystalline proteins.

Sulfur-containing sites in proteins are of great importance for both protein structure and function, including enzymatic catalysis, signaling pathways, and recognition of ligands and protein partners. Selenium-77 is an NMR active spin-1/2 nucleus that shares many physiochemical properties with sulfur and can be readily introduced into proteins at sulfur sites without significant perturbations to the protein structure. The sulfur-containing amino acid methionine is commonly found at protein-protein or protein-ligand binding sites. Its selenium-containing counterpart, selenomethionine, has a broad chemical shift dispersion useful for NMR-based studies of complex systems. Methods such as (1H)-77Se-13C double cross polarization or {77Se}-13C REDOR could be valuable to map the local environment around selenium sites in proteins but have not been demonstrated to date. In this work, we explore these dipolar transfer mechanisms for structural characterization of the GB1 V39SeM variant of the model protein GB1 and demonstrate that 77Se-13C based correlations can be used to map the local environment around selenium sites in proteins. We have found that the general detection limit is ~ 5Å, but longer range distances up to ~ 7Å can be observed as well. This study establishes a framework for the future characterization of selenium sites at protein-protein or protein-ligand binding interfaces.

Atomically Dispersed Selenium Sites on Nitrogen‐Doped Carbon for Efficient Electrocatalytic Oxygen Reduction

AbstractOwing to their unique electronic structure and maximum atom utilization efficiency, single‐atom catalysts have received widespread attention and exhibited efficient activity. Herein, we report the preparation of non‐metal Se single atoms embedded in nitrogen‐doped carbon (NC) via a high‐temperature reduction strategy for electrocatalytic oxygen reduction reaction (ORR). Selenium dioxide is reduced to selenium by NC at high temperature and partially anchored to form C−Se−C bond. Impressively, the obtained single‐atom catalyst exhibits outstanding ORR activity and stability that even surpasses state‐of‐the‐art noble metal catalysts and many previously reported nanocatalysts. Experimental and theoretical calculations reveal that the Se single atoms can serve as the ORR active sites and contribute to lowering the reaction barrier. Our discoveries demonstrate the promising prospects for utilizing metal‐free single‐atom‐based materials for efficient electrocatalysis.

Atomically Dispersed Selenium Sites on Nitrogen‐Doped Carbon for Efficient Electrocatalytic Oxygen Reduction

Owing to their unique electronic structure and maximum atom utilization efficiency, single-atom catalysts have received widespread attention and exhibited efficient activity. Herein, we report the preparation of non-metal Se single atoms embedded in nitrogen-doped carbon (NC) via a high-temperature reduction strategy for electrocatalytic oxygen reduction reaction (ORR). Selenium dioxide is reduced to selenium by NC at high temperature and partially anchored to form C-Se-C bond. Impressively, the obtained single-atom catalyst exhibits outstanding ORR activity and stability that even surpasses state-of-the-art noble metal catalysts and many previously reported nanocatalysts. Experimental and theoretical calculations reveal that the Se single atoms can serve as the ORR active sites and contribute to lowering the reaction barrier. Our discoveries demonstrate the promising prospects for utilizing metal-free single-atom-based materials for efficient electrocatalysis.

Optically active selenium vacancies in BaGa4Se7 crystals

Barium gallium selenide (BaGa4Se7) is a recently developed nonlinear optical material with a transmission window extending from 470 nm to 17 μm. A primary application of these crystals is the production of tunable mid-infrared laser beams via optical parametric oscillation. Unintentional point defects, such as selenium vacancies, cation vacancies (barium and/or gallium), and trace amounts of transition-metal ions, are present in BaGa4Se7 crystals and may adversely affect device performance. Electron paramagnetic resonance (EPR) and optical absorption are used to identify and characterize these defects. Five distinct EPR spectra, each representing an electron trapped at a selenium vacancy, are observed at low temperature (there are seven crystallographically inequivalent selenium sites in the crystal). One spectrum is stable at room temperature and is present before illumination. The other four are produced at lower temperatures with 532 nm laser light and are thermally unstable at room temperature. Each S = 1/2 singly ionized selenium vacancy has a large, nearly isotropic, hyperfine interaction with 69Ga and 71Ga nuclei at one neighboring Ga site. A significant portion of the unpaired spin resides in a 4s orbital on this adjacent Ga ion and gives principal values of the hyperfine matrices in the 3350–6400 MHz range. Broad photoinduced optical absorption bands in the visible and near-infrared are assigned to the selenium vacancies.

Engineering MoSe2/WS2 Hybrids to Replace the Scarce Platinum Electrode for Hydrogen Evolution Reactions and Dye-Sensitized Solar Cells.

In recent times, two-dimensional transition-metal dichalcogenides (TMDs) have become extremely attractive and proficient electrodes for dye-sensitized solar cells (DSSCs) and water electrolysis hydrogen evolution as alternatives to the scarce metal platinum (Pt). The active TMD molybdenum selenide (MoSe2) and tungsten disulfide (WS2) are inspiring systems owing to their abundance of active sulfur and selenium sites, but their outputs are lacking due to their inactive basal planes and ineffective transport behavior. In this work, van der Waals interrelated MoSe2/WS2 hybrid structures were constructed on conducting glass substrates by chemicophysical methodologies. For the first time, the constructed MoSe2/WS2 structures were effectively used as a counter electrode for DSSCs and an active electrode for hydrogen evolution to replace the nonabundant Pt. The assembled DSSCs using the designed MoSe2/WS2 heterostructure counter electrode provided a superior power-conversion efficiency of 9.92% and a photocurrent density of 23.10 mA·cm-2, unmatchable by most of the TMD-based structures. The MoSe2/WS2 heterostructure displayed excellent electrocatalytic hydrogen evolution behavior with a 75 mV overpotential to drive a 10 mA·cm-2 current density, a 60 mV·dec-1 Tafel slope, and an over 20 h durable process in an acidic medium. The results demonstrated the advantages of the MoSe2/WS2 hybrid development for generating interfacial transport and active facet distribution and enriching the electrocatalytic activity for DSSCs and the water-splitting hydrogen evolution process.

Optimized nanospace of coordination isomers with selenium sites for acetylene separation

Assisted by functional Cu and Se sites, a new group of porous isomers demonstrated systematically tunable C2H2/CO2separation.

Transport and structural properties of Cu0.25Bi2(TexSe1−x)3 (x = 0.01) under high pressure

Cu0.25Bi2(TexSe1−x)3 is a material in which tellurium atoms (Te) partially occupy selenium (Se) sites in a crystal structure of the superconductor Cu0.25Bi2Se3. This study focuses on the composition of x = 0.01, Cu0.25Bi2(Te0.01Se0.99)3, and we performed electrical resistivity measurement and X-ray diffraction under high pressures. Cu0.25Bi2(Te0.01Se0.99)3 shows slight diamagnetism and a drop in resistivity at ambient pressure; this suggests possible superconductivity at the transition temperature of Tc = 3.2 K, which is suppressed at P = 1 GPa. On further compression, a slight drop in resistivity is observed at temperatures of 4.3–5.4 K above 10 GPa. This drop is suppressed under magnetic fields, suggesting the occurrence of superconducting transition. The pressure-induced structural phase transition from a trigonal phase to a sevenfold monoclinic C2/m phase occurs at 10.9 GPa. These results suggest that the superconducting transition above 10 GPa occurs in the high-pressure C2/m phase.

Selenium Redox Reactivity on Colloidal CdSe Quantum Dot Surfaces

Understanding the structural and compositional origins of midgap states in semiconductor nanocrystals is a longstanding challenge in nanoscience. Here, we report a broad variety of reagents useful for photochemical reduction of colloidal CdSe quantum dots, and we establish that these reactions proceed via a dark surface prereduction step prior to photoexcitation. Mechanistic studies relying on the specific properties of various reductants lead to the proposal that this surface prereduction occurs at oxidized surface selenium sites. These results demonstrate the use of small-molecule inorganic chemistries to control the physical properties of colloidal QDs and provide microscopic insights into the identities and reactivities of their localized surface species.

Effect of Surface Stoichiometry on Blinking and Hole Trapping Dynamics in CdSe Nanocrystals

We measure the photoinduced carrier dynamics as the surface composition of CdSe nanocrystals is systematically varied from metal rich (∼80% surface Cd) to nearly stoichiometric (∼50% surface Cd). Using time-resolved optical spectroscopy, we determine that the luminescence lifetime is controlled by the rate of hole trapping at the newly exposed surface selenium atoms. However, the increased rate of the photoluminescence decay is not sufficient to explain the decreased photoluminescence quantum yield, and requires a growing proportion of nanocrystals in a dark or “OFF” state to explain the data. A global kinetic model is proposed that relates the fraction of selenium sites to the rate of hole trapping. A linear relationship between the rate of hole trapping and the fraction of exposed Se sites (xSe) is observed within the range of accessible stoichiometries (xSe = 0.5–0.2). Extrapolation to higher surface cadmium fractions suggests that not all Se sites serve as effective hole traps. These results explain t...

Structural and Functional Study of d-Glucuronyl C5-epimerase

Heparan sulfate (HS) is a glycosaminoglycan present on the cell surface and in the extracellular matrix, which interacts with diverse signal molecules and is essential for many physiological processes including embryonic development, cell growth, inflammation, and blood coagulation. D-glucuronyl C5-epimerase (Glce) is a crucial enzyme in HS synthesis, converting D-glucuronic acid to L-iduronic acid to increase HS flexibility. This modification of HS is important for protein ligand recognition. We have determined the crystal structures of Glce in apo-form (unliganded) and in complex with heparin hexasaccharide (product of Glce following O-sulfation), both in a stable dimer conformation. A Glce dimer contains two catalytic sites, each at a positively charged cleft in C-terminal α-helical domains binding one negatively charged hexasaccharide. Based on the structural and mutagenesis studies, three tyrosine residues, Tyr(468), Tyr(528), and Tyr(546), in the active site were found to be crucial for the enzymatic activity. The complex structure also reveals the mechanism of product inhibition (i.e. 2-O- and 6-O-sulfation of HS keeps the C5 carbon of L-iduronic acid away from the active-site tyrosine residues). Our structural and functional data advance understanding of the key modification in HS biosynthesis.