Dissolution Of Se Research Articles

High-Capacity and Ultra-Long-Life Mg-Metal Batteries Enabled by Intercalation-Conversion Hybrid Cathode Materials.

The advancement of rechargeable Mg-metal batteries (RMBs) is severely impeded by the lack of suitable cathode materials. Despite the good cyclic stability of intercalation-type compounds, their specific capacity is relatively low. Conversely, the conversion-type cathodes can deliver a higher capacity but often suffer from poor cycling reversibility and stability. Herein, a WSe2/Se intercalation-conversion hybrid material with elemental Se uniformly distributed into WSe2 nanosheets is fabricated via a simple solvothermal method for high-performance RMBs. The uniformly introduced Se confined in WSe2 nanosheets can not only efficiently improve the conductivity of the hybrid cathodes, facilitating the fast electron transport and ion diffusion, but also provide additional specific capacity. Besides, the WSe2 can effectively inhibit the detrimental Se dissolution and polyselenide shuttle, thereby activating the activity of Se and improving its utilization. Consequently, the synergy of intercalation and conversion mechanisms endows WSe2/Se hybrids with superior reversible capacity of 252mAhg-1at 0.1Ag-1 and ultra-long cyclability of up to 5000 cycles at 2.0Ag-1 with capacity retention of 78.1%. This work demonstrates the feasibility of the strategy by integrating intercalation and conversion mechanisms for developing high-performance cathode materials for RMBs.

Multiscale structural engineering of Co0.85Se@porous carbon composite enables highly reversible lithium/sodium storage

Cobalt selenide (Co0.85Se) has been regarded as the most potential anode material for both lithium/sodium ion batteries (LIBs and SIBs) due to its high specific capacity and excellent pseudocapacitive effect. However, the inevitable volume expansion during conversion reaction and grievous dissolution of Se in electrolytes seriously undermine its reversibility and cycling stability. Combining the transition-metal chalcogenides with stable porous carbon networks is considered as one of the most effective strategies to improve electrochemical stability and conductivity of transition-metal chalcogenides. Here, we proposed a multiscale structural engineering strategy to encapsulate selenide nanoparticles in N-doped porous carbon to enable high-performance Co0.85Se@porous carbon composite for highly reversible lithium/sodium storage. Specifically, the Co0.85Se nanoparticles are tightly anchored to carbon network through substantial SeC bond, which effectively buffer volume expansion and inhibit the dissolution of Se in electrolytes. Additionally, the carbon pores with multilevel size help achieving the fast ions diffusion. The unique structure enables the Co0.85Se composite anode to exhibit excellent discharge capacities of 955.1 mAh g−1 at 100 mA g−1 after 100 cycles, 305.6 mAh g−1 at 1 A g−1 of full cells after 550 cycles in LIBs and 491.3 mAh g−1 at 100 mA g−1 after 100 cycles in SIBs.

Bi2Se3@SWCNT heterostructures with beyond theoretical capacity as perspective binder-free anodes for lithium-ion batteries

Bi2Se3 has shown potential for implementation as an anode material for lithium-ion batteries (LIBs), however, the significant volume expansion and dissolution of selenium pose major challenges. In this work, Bi2Se3 nanostructures are synthesized by physical vapor deposition directly on top of a single-wall carbon nanotube (SWCNT) network to fabricate a binder-free Bi2Se3@SWCNT anode materials with different Bi2Se3/SWCNT ratios. Nanostructuring the Bi2Se3 directly on the top of the SWCNT network provides a large accessible contact area and improves mechanical and electrical contact. The heterostructures exhibit capacity, that is beyond the theoretical of pristine Bi2Se3, which can be attributed to the binding of the Se to C, resulting in the resilience against the dissolution of Se, while providing additional electron transport pathways and increased capacitive contribution. A Bi2Se3@SWCNT anode with a mass ratio of (1:1) has the highest capacity in a half-cell after 100 cycles (523 mAh g−1 at 0.1 A g−1) and shows excellent capacity retention after 500 cycles at large current densities (2 A g−1 and 5 A g−1): 1080 mAh g−1 and 809 mAh g−1 respectively. In addition, in a full-cell system Bi2Se3@SWCNT (1:1) delivers high reversible capacity after 150 cycles (484 mAh g−1) at 0.4 A g−1.

CMK3 collaborated with SexSy to build high-performance rechargeable aluminum-ion batteries

The development of rechargeable aluminum batteries (RABs) has consistently relied on the logical selection and design of cathode materials. Se has a high electrical conductivity while S has a high theoretical specific capacity; yet, both materials are known to present lethal shuttle effects, space expansion, and slow reaction kinetics. The development of RABs will be accelerated if the synergistic properties of both materials can be utilized. Various ratios of SexSy as the cathode materials for RABs, and a series of electrochemical tests are shown in this work. The rise in the ratio of Se and S leads to the improvement of the cycling performance. However, the shuttle effect of Se and S has a fatal blow to the performance of the battery. To solve this problem, (mesostructured carbon materials) CMK3 modified separators were employed between the cathode and anode to further limit the dissolution of Se, considerably improving the utilization of the active materials. Therefore, initial capacity of Al/GF/C@CMK-3/SexSy is about 539.4 mAh g−1 and reversible capacity of 314.2 mAh g−1 was likewise maintained after 500 cycles at 1.0 A g−1. RABs based on Al/S and Al/Se batteries have promising research avenues opened up by Al/SexSy batteries based on CMK3 modified separators.

Boosting Alkaline Hydrogen Evolution Reaction via an Unexpected Dynamic Evolution of Molybdenum and Selenium on MoSe2 Electrode

AbstractTransition metal chalcogenides are a promising and extremely pivotal class of electrocatalysts with potential applications in alkaline hydrogen evolution reaction (HER), especially, molybdenum diselenide. Although the exposed edge sites are generally considered to be the active sites of MoSe2 for HER, an intrinsic behavior (surface species evolution, structure/morphology conversion, stability) of MoSe2 electrode itself was not unveiled. Herein, the origin of MoSe2‐electrocatalyzed HER activity monitored by the quasi‐operando XPS and in situ Raman spectroscopy is presented. The findings clearly show dynamic evolution of both Mo and Se species on MoSe2 electrode surface for promoting HER activity and maintaining long‐term catalytic stability and reveal an electro‐oxidative dissolution and re‐adsorption mechanism. Theoretical calculations also corroborate these results. As expected, the addition of single or mixed MoO42− and SeO32− to the electrolyte of nickel foam directly verifies the critical role of surface‐adsorbed Mo and Se species for boosting HER activity and stability. Additionally, the oxidative dissolution of Se on NixSey electrode surface during HER is also observed, revealing the universality of oxidative dissolution of Se in transition metal selenides. This study provides a unique insight into the species evolution and surface structure transformation mechanism and activity improved origin of materials during the electroreduction process.

Redox Interaction between Selenite and Mackinawite in Cement Pore Water.

In cement-rich radioactive waste repositories, mackinawite (FeS) forms at the steel corrosion interface within reinforced concrete and potentially retards the transport of redox-sensitive radionuclides (e.g., 79Se) in porous cement media. Redox interactions between selenite and mackinawite under hyperalkaline conditions remain unclear and require further investigations. Here, using comprehensive characterization on both aqueous and solid speciation, we successfully monitored the whole interaction process between selenite and mackinawite under hyperalkaline conditions. The results show similar chemical environments for SeO32- and S2-/Sn2- at the mackinawite-water interface, verifying an immediate reduction. After 192 h of reaction, SeO32- was reduced to solid Se0 and SeS2 species, accompanied by the oxidation of S2-/Sn2- to S2O32- and Fe(II) to Fe(III) in mackinawite. Aqueous speciation results showed that ∼99% of aqueous selenium was present as Se4S nanoparticles due to the dissolution of Se from the solid. In parallel, ∼62% of S2-/Sn2- was released into the solution, with mackinawite transforming into magnetite, Fe(OH)3 and FeS2O3+ complexed to Cl- or OH- species, and magnetite subsequently dispersed in the solution. This study provides valuable data about the retardation mechanisms of redox-sensitive radionuclides by soluble iron sulfides, which is critical to advance our understanding of reactive concrete barriers used in nuclear waste disposal systems.

Effects of Corrosion Products Deposited on 304 Stainless Steel on Reduction of Se (IV/VI) in Simulated Groundwater.

Selenium (Se) is a key mobile fission product in the geological disposal of nuclear waste. It is necessary to analyze the reductive deposition behavior of iron-based materials to Se(IV) and Se(VI) in groundwater. In the present work, the corrosion behavior of 304 stainless steel in simulated groundwater (SG) and the effects of corrosion products on the dissolution of Se were investigated by electrochemical and immersion tests. Experimental results revealed that passivation films formed on 304 stainless-steel samples were destroyed by polarization measurements, forming corrosion products consisting of Fe(II) compounds, such as Fe3O4 and FeO. Corrosion products deposited on the surface of steel samples previously treated by polarization measurements in SG + CaCl2/Na2CO3/Na2SiO3 solutions effectively reduced soluble Se(IV) and Se(VI) during immersion tests, depositing FeSe2 on sample surfaces.

A comparative study exploring the ligand binding capabilities of quarternary chalcopyrite copper indium gallium diselenide (CIGSe) nanocrystals

Recent study investigates employment of differently-capped chalcopyrite Copper Indium Gallium Diselenide (CIGSe) wherein; binding abilities of three different capping ligands have been studied. Oleylamine (OLA), Oleic acid (OA) and the combination of oleylamine-oleic acid (OLA+OA) have been chosen as basic ligands in addition to dodecanethiol as a source for attaining Se dissolution that is otherwise difficult during utilization of pristine ligands. The overall combination has also led to the formation of well-stabilized nanocrystals. The work also envisages an approach towards low-cost, environmentally-friendly processing of active absorber CIGSe layers by various parametric variations; emphasizing primarily on the adoption of green route method for overcoming the toxicity constraints in the preparation of CIGSe nanocrystals.

Potential Pollution of Groundwater by Dissolution and Release of Contaminants due to Using Gangue for Backfilling

Large quantities of solid wastes, including gangue (waste rock) have been added to the goafs in China’s coal mines as backfill. In this study, the mineral and chemical compositions of gangue from the No. 12 coal mine of the Pingdingshan Coal Group were investigated to determine potential pollution concerns, and the behaviour of contaminants in the gangue, such as salts, alkali metals, and alkaline earth metals, was explored using static immersion tests. COMSOL Multiphysics was used to study contaminant migration. The concentration and diffusion distance of metal ions were found to increase over time; this was negatively correlated with gangue particle size. Acidic environments promoted the dissolution of Ca, Fe, Mn, Na, Zn, Pb, and Be, while in alkaline environments, Se dissolution was accelerated.

Role of extracellular reactive sulfur metabolites on microbial Se(0) dissolution.

The dissolution of elemental selenium [Se(0)] during chemical weathering is an important step in the global selenium cycle. While microorganisms have been shown to play a key role in selenium dissolution in soils, the mechanisms of microbial selenium solubilization are poorly understood. In this study, we isolated a Bacillus species, designated as strain JG17, that exhibited the ability to dissolve Se(0) under oxic conditions and neutral pH. Growth of JG17 in a defined medium resulted in the production and accumulation of extracellular compounds that mediated Se(0) dissolution. Analysis of the spent medium revealed the presence of extracellular sulfite, sulfide, and thiosulfate. Abiotic Se(0) dissolution experiments with concentrations of sulfite, sulfide, and thiosulfate relevant to our system showed similar extents of selenium solubilization as the spent medium. Together, these results indicate that the solubilization of Se(0) by JG17 occurs via the release of extracellular inorganic sulfur compounds followed by chemical dissolution of Se(0) by the reactive sulfur metabolites. Our findings suggest that the production of reactive sulfur metabolites by soil microorganisms and the formation of soluble selenosulfur complexes can promote selenium mobilization during chemical weathering.

Electrodeposition of lead selenide films from ionic liquids based on choline chloride

The paper presents some experimental results regarding the electrodeposition of PbSe thin films at 70 °C from two choline chloride (ChCl) based ionic liquids containing PbCl2 and SeO2 as precursors in choline chloride-ethylene glycol (ILEG) and choline chloride-urea (IL) eutectic mixtures. In this article we will detail our investigation of cathodic processes involved during the electrodeposition of binary semiconductor compound, PbSe as well as of singular Pb and Se elements. The cathodic branches of the recorded cyclic voltammograms in the cases of ionic liquids containing both Pb2+ + Se4+ show successively the Se underpotential deposition, Se bulk deposition and Pb deposition followed by a formation of PbSe semiconductor compound. However, at the most negative potentials the Se content of final layers decreases by a partial electrochemical dissolution of Se which reduces to Se2− soluble species.PbSe thin films have been electrodeposited on copper or nickel substrates under potentiostatic control at 70 °C for 0.5–4 h. The adherent and uniform deposits were characterized by SEM-EDX and XRD techniques. SEM images have shown adherent and grey deposits with uniform morphology and cubic PbSe crystals. A stoichiometry of around Pb1.1Se was indicated by EDX elemental analysis. XRD confirmed the formation of PbSe compound, showing a nanocrystalline structure, with crystallites average sizes in the range of 10–35 nm.

Stable Carbon–Selenium Bonds for Enhanced Performance in Tremella‐Like 2D Chalcogenide Battery Anode

Abstract2D cobalt selenide based on conversion reaction has attracted much attention due to its open layered structure and high specific capacity. However, effectively suppressing the fast capacity fade caused by the irreversible Se dissolution and serious volume change during the cycling process is still a challenge. Herein, the concentration of dispersion liquid under supercritical conditions is tuned to induce the CoSe crystal to grow along the graphene oxide (GO), and finally obtain the Tremella‐like CoSe–reduced GO (rGO) hybrid. The nature of epitaxial growth leads to the formation of stable CSe bonds, which maintain a favorable conductive connection between CoSe and rGO as well as enhance the mechanical strength of active materials to suppress Se dissolution and volume expansion during Na/Li intercalation and deintercalation. The unique microstructural merits of the hybrid result in superior sodium/lithium storage performance (400.8 mAh g−1 at 1 A g−1 after 100 cycles for sodium‐ion batteries and 769.6 mAh g−1 at 2 A g−1 after 500 cycles for lithium‐ion batteries). Moreover, the transmission X‐ray microscopy technique is first used to directly observe the Se segregation in cobalt selenide and it being suppressed by the CSe bonds.

Direct solution deposition of device quality Sb2S3-xSex films for high efficiency solar cells

Sb2S3-xSex (0 ≤x ≤ 3) is promising for practically applicable solar cell since it possesses excellent stability, suitable band gap, high extinction coefficient and abundant elemental storage. This study demonstrates a novel methodology towards simultaneous dissolution of Se and Sb2O3 for direct deposition of Sb2S3-xSex films. Mechanistic study shows that the formation of selenium-nitrogen free radical in sulfur-containing complex is responsible for the dissolution of selenium. The energy levels of the as-synthesized Sb2S3-xSex were examined by synchrotron radiation photoemission spectroscopy, revealing that more Se in the Sb2S3-xSex leads to the valence band shifting considerably upward while the conduction band remaining nearly unchanged. Moreover, for the first time we present that the solution processed Sb2S3-xSex can generate photovoltaic performance with an efficiency of 5.8%. This research provides a straightforward strategy for the fabrication of Sb2S3-xSex solar cells and offers an effective method for the synthesis of metal selenosulfide films.

Alkylthiol-enabled Se powder dissolving for phosphine-free synthesis of highly emissive, large-sized and spherical Mn-doped ZnSeS nanocrystals

The enhanced dissolution of Se without organo-phosphines is a key issue in the synthesis of oil-soluble selenide nanocrystals.

High-quality Cu2ZnSnS4 and Cu2ZnSnSe4 nanocrystals hybrid with ZnO and NaYF4: Yb, Tm as efficient photocatalytic sensitizers

A chloroform-assistant Se dissolution in oleylamine without trioctylphosphine and alkylthiol as the green precursor was used for facile and robust synthesis of quaternary selenide nanocrystals. The S2− modified hydrophilic Cu2ZnSnS4 and Cu2ZnSnSe4 nanocrystals were first prepared by a one-pot thermal decomposition route, followed by a bi-phase hydrophilic treatment process. As a proof of concept, the as-obtained hydrophilic nanocrystals were hybridized with ZnO microspheres as photosensitizers to achieve visible light-driven photocatalytic application; on the other hand, hybridized with NaYF4: Yb, Tm microplates to achieve near-infrared light-driven photocatalytic application. These photosensitized hybrids as photocatalysts expanded the light absorption from ultraviolet to visible even near-infrared region, which showed excellent photocatalytic Rhodamine B degradation under visible and near-infrared irradiation compared to pure ZnO and NaYF4: Yb, Tm, respectively. Therefore, these hydrophilic Cu2ZnSnS4 and Cu2ZnSnSe4 nanocrystals are proved as efficient photocatalytic sensitizers due to the efficient utilization of the visible light and emissions upconverted from near-infrared light.

Cellular and Transcriptional Response of Pseudomonas stutzeri to Quantum Dots under Aerobic and Denitrifying Conditions

Pseudomonas stutzeri was exposed to quantum dots (QDs) with three different surface coatings (anionic polymaleic anhydride-alt-1-octadecene (PMAO), cationic polyethylenimine (PEI), and carboxyl QDs) under both aerobic and anaerobic (denitrifying) conditions. Under aerobic conditions, toxicity (assessed per growth inhibition) increased from PMAO to carboxyl to PEI QDs. The positive charge of PEI facilitated direct contact with negatively charged bacteria, which was verified by TEM analysis. Both PMAO and PEI QDs hindered energy transduction (indicated by a decrease in cell membrane potential), and this effect was most pronounced with PEI QDs under denitrifying conditions. Up-regulation of denitrification genes (i.e., nitrate reductase narG, periplasmic nitrate reductase napB, nitrite reductase nirH, and NO reductase norB) occurred upon exposure to subinhibitory PEI QD concentrations (1 nM). Accordingly, denitrification activity (assessed per respiratory nitrate consumption in the presence of ammonia) increased during sublethal PEI QD exposure. However, cell viability (including denitrification) was hindered at 10 nM or higher PEI QD concentrations. Efflux pump genes czcB and czcC were induced by PEI QDs under denitrifying conditions, even though Cd and Se dissolution from QDs did not reach toxic levels (exposure was at pH 7 to minimize hydrolysis of QD coatings and the associated release of metal constituents). Up-regulation of the superoxide dismutase (stress) gene sodB occurred only under aerobic conditions, likely due to intracellular production of reactive oxygen species (ROS). The absence of ROS under denitrifying conditions suggests that the antibacterial activity of QDs was not due to ROS production alone. Overall, this work forewarns about unintended potential impacts to denitrification as a result of disposal and incidental releases of QDs, especially those with positively charged coatings (e.g., PEI QDs).

The processes involved in the Se electrodeposition and dissolution on Au electrode: the H2Se formation

The processes involved in the Se electrodeposition, mainly the one related to the formation of H2Se species on Au electrode in perchloric acid solutions, have been investigated through cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM), rotating ring-disc electrode (RRDE), and atomic force microscopy (AFM) techniques. In the experiments performed with the EQCM, with the potential sweep in the negative direction, the responses for the mass variation were divided in three well-defined potential regions: A (from 1.55 to 0.35 V), B (from 0.35 to −0.37 V), and C (from −0.37 to −0.49 V). It was verified that the following processes can occur, respectively: the species (AuO)2H2SeO3 was desorbed during the AuO reduction, the reduction of Se(IV) to Se(0), and the formation of H2Se. When the potential was swept in the positive direction, the responses for the mass variation were divided in four well-defined potential regions: D (from −0.49 to 0.66 V), E (from 0.66 to 0.99 V), F (from 0.99 to 1.26 V), and G (from 1.26 to 1.55 V), and the described processes in these regions were, respectively: the Se deposition and adsorption of water molecules and/or perchlorate ions, the Se dissolution, the Se incorporating mass in the form of HO–Se, and the Au oxidation (all potentials are referred to the Ag/AgCl electrode). Making use of the RRDE, using the collection technique, the formation of H2Se species during the Se electrodeposition was investigated. Therefore, it was confirmed that this species is formed on the disc electrode between −0.3 and −0.55 V vs the Ag/AgCl potential range (collecting the oxidized compound onto the ring electrode). AFM images also indicated that the surface topography of the Se-massive deposit on Au is different from the images registered after the formation of H2Se species, confirming the cathodic stripping of Se.

Microgravimetric, rotating ring-disc and voltammetric studies of the underpotential deposition of selenium on polycrystalline platinum electrodes

Selenium underpotential deposition (upd) on platinum electrodes in perchloric acid solutions was analysed by cyclic voltammetry, rotating ring-disc electrode, and electrochemical quartz crystal microbalance techniques. From the results obtained for Se upd on Pt, the presence of two peaks in the positive sweep with a total charge density value of 420 μC cm −2 (found after subtraction of the charge density due to PtO from the total charge density) was observed. These results are attributed to the deposition of one Se monolayer on Pt with the occupation of two active substrate sites by each Se ad-atom. Such results were confirmed by rotating ring-disc electrode experiments. In the electrochemical quartz crystal microbalance experiments the responses for mass variations were divided in three well-defined potential regions: (A) (0.05–0.7 V), (B) (0.7–1.1 V) and (C) (1.1–1.55 V) in which the mass values of: +18, −50 and −28 ng cm −2, respectively, were described by: (i) water adsorption on previously deposited Se, (ii) dissolution of the species (Se + H 2O) and (iii) dissolution of Se and formation of Pt oxide. The electrode process can be represented according to the reaction: SeO 2 + 4H + + 4e − ⇋ Se ads 0 + 2H 2O.

Soil and plant selenium at a reclaimed uranium mine.

Selenium (Se) associated with reclaimed uranium (U) mine lands may result in increased food chain transfer and water contamination. To assess post-reclamation bioavailability of Se at a U mine site in southeastern Wyoming, we studied soil Se distribution, dissolution, speciation, and sorption characteristics and plant Se accumulation. Phosphate-extractable soil Se exceeded the critical limit of 0.5 mg/kg in all the samples, whereas total soil Se ranged from a low (0.6 mg/kg) to an extremely high (26 mg/kg) value. Selenite was the dominant species in phosphate and ammonium bicarbonate-diethylenetriamine pentaacetic acid (AB-DTPA) extracts, whereas selenate was the major Se species in hot water extracts. Extractable soil Se concentrations were in the order of KH2PO4 > AB-DTPA > hot water > saturated paste. The soils were undersaturated with respect to various Se solid phases, albeit with high levels of extractable Se surpassing the critical limit. Calcium and Mg minerals were the potential primary solids controlling Se dissolution, with dissolved organic carbon in the equilibrium solutions resulting in enhanced Se availability. Adsorption was a significant (r2 = 0.76-0.99 at P < 0.05) mechanism governing Se availability and was best described by the initial mass isotherm model, which predicted a maximum reserve Se pool corresponding to 87% of the phosphate-extractable Se concentrations. Grasses, forbs, and shrubs accumulated 11 to 1800 mg Se/kg dry weight. While elevated levels of bioavailable Se may be potentially toxic, the plants accumulating high Se may be used for phytoremediation, or the palatable forage species may be used as animal feed supplements in Se-deficient areas.

Investigation of Electrochemical Processes for Synthesis and Removal of CuInSe2 Thin Films

AbstractElectrochemical deposition of CuInSe2 films has been explored as a low-cost alternative to vacuum deposition. A special feature of this approach is that each element or compound may be selectively deposited or dissolved at a specific potential. This approach could further provide an environmentally benign means to recycle CuInSe2 from spent or defective modules. The paper investigates the reaction mechanisms for co-deposition, as well as, removal of CuInSe2. Rotating ring-disk and photoelectrochemical methods probe the formation and dissolution of Se, Cu2Se, In2Se3 and CuInSe2 films and the corrosion of CuInSe2 single crystal. The results provide important insights into the multiple reaction paths leading to the electrosynthesis of CuInSe2 films and new directions for developing an electrochemical recycling scheme for CuInSe2 modules.