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―Compound Cu 3 NaS 2 has been prepared by solid-phase reactions from copper and sodium sulfides Cu 2 S and Na 2 S. It has been shown that compound Cu 3 NaS 2 has hexagonal structure with lattice parameters a = 13.9398 ± 23 Å and c = 21.4637 ± 74 Å. After 6 months after synthesis, compound Cu 3 NaS 2 spontaneously transforms at ambient temperature from hexagonal structure into phase with face-centered cubic (FCC) lattice. The dimension of coherent-scattering regions ( CSR ) for the FCC phase determined from the broadening of diffraction lines varies from ~25 nm at ambient temperature to ~110 nm at 500°C. DSC curves show anomalies at temperatures of 108 and 436°C corresponding to endothermal reversible transitions without change in the type of crystal lattice. The authors consider these anomalies to be due to redistribution of copper and sodium cations over possible crystallographic positions.

Sodium sulfate (Na2SO4) is used in the ecofriendly production of sodium sulfide (Na2S) through H2 reduction, thereby facilitating the valorization of Na2SO4. However, studies on this technique remain at the laboratory stage. This paper proposes a novel process involving the external circulation of Na2S in a dilute-phase fluidized system to address the low-temperature eutectic formation between Na2S and Na2SO4 during the H2 reduction of Na2SO4 to Na2S. The process aims to increase the reaction temperature of the Na2SO4 while reducing the volume of the liquid phase formed to prevent sintering blockages and enhance the reduction rate. In a proprietary experimental setup, the H2 reduction process in a dilute-phase fluidized system was investigated. The Na2S/Na2SO4 ratio and reaction temperature were determined to be critical factors influencing the Na2SO4 reduction rate. The melting point of the system increased and the amount of liquid phase produced decreased as the Na2S content was increased to more than 60%. The Na2S–Na2SO4 mixture (mass ratio of 80:20) existed as a solid at the reaction temperature of 740 °C. After roasting for 10 s, the Na2SO4 reduction rate reached 93.7% and the Na2S content in the mixture increased to 98.74%.

Acetogenesis and methanogenesis have attracted attention as CO2-fixing reactions. Humin, a humic substance insoluble at any pH, has been found to assist CO2-fixing acetogenesis as the sole electron donor. Here, using two CO2-fixing consortia with acetogenic and methanogenic activities, the effect of various parameters on these activities was examined. One consortium utilized humin and hydrogen (H2) as electron donors for acetogenesis, either separately or simultaneously, but with a preference for the electron use from humin. The acetogenic activity was accelerated 14 times by FeS at 0.2 g/L as the optimal concentration, while being inhibited by MgSO4 at concentration above 0.02 g/L and by NaCl at concentrations higher than 6 g/L. Another consortium did not utilize humin but H2 as electron donor, suggesting that humin was not a universal electron donor for acetogenesis. For methanogenesis, both consortia did not utilize extracellular electrons from humin unless H2 was present. The methanogenesis was promoted by FeS at 0.2 g/L or higher concentrations, especially without humin, and with NaCl at 2 g/L or higher concentrations regardless of the presence of humin, while no significant effect was observed with MgSO4. Comparative sequence analysis of partial 16S rRNA genes suggested that minor groups were the humin-utilizing acetogens in the consortium dominated by Clostridia, while Methanobacterium was the methanogen utilizing humin with H2.

The rigorous environmental requirements promote the development of new processes with short and clean technical routes for recycling tellurium from tellurium-bearing sodium carbonate slag. In this paper, a novel process for selective recovery of tellurium from the sodium carbonate slag by sodium sulfide leaching, followed by cyclone electrowinning, was proposed. 88% of tellurium was selectively extracted in 40 g/L Na2S solution at 50 °C for 60 min with a liquid to solid ratio of 8:1 mL/g, while antimony, lead and bismuth were enriched in the leaching residue. Tellurium in the leach liquor was efficiently electrodeposited by cyclone electrowinning without purification. The effects of current density, temperature and flow rate of the electrolyte on current efficiency, tellurium recovery, cell voltage, energy consumption, surface morphology, and crystallographic orientations were systematically investigated. 91.81% of current efficiency and 95.47% of tellurium recovery were achieved at current density of 80 A/m2, electrolyte temperature of 45 °C and electrolyte flow rate of 400 L/h. The energy consumption was as low as 1.81 kWh/kg. A total of 99.38% purity of compact tellurium deposits were obtained. Therefore, the proposed process may serve as a promising alternative for recovering tellurium from tellurium-bearing sodium carbonate slag.

High-temperature sodium–sulfur batteries operating at 300–350 °C have been commercially applied for large-scale energy storage and conversion. However, the safety concerns greatly inhibit their widespread adoption. Herein, we report a room-temperature sodium–sulfur battery with high electrochemical performances and enhanced safety by employing a “cocktail optimized” electrolyte system, containing propylene carbonate and fluoroethylene carbonate as co-solvents, highly concentrated sodium salt, and indium triiodide as an additive. As verified by first-principle calculation and experimental characterization, the fluoroethylene carbonate solvent and high salt concentration not only dramatically reduce the solubility of sodium polysulfides, but also construct a robust solid-electrolyte interface on the sodium anode upon cycling. Indium triiodide as redox mediator simultaneously increases the kinetic transformation of sodium sulfide on the cathode and forms a passivating indium layer on the anode to prevent it from polysulfide corrosion. The as-developed sodium–sulfur batteries deliver high capacity and long cycling stability. Sodium–sulfur batteries operating at a high temperature between 300 and 350°C have been used commercially, but the safety issue hinders their wider adoption. Here the authors report a “cocktail optimized” electrolyte system that enables higher electrochemical performance and room-temperature operation.

The low-cost room-temperature sodium-sulfur battery system is arousing extensive interest owing to its promise for large-scale applications. Although significant efforts have been made, resolving low sulfur reaction activity and severe polysulfide dissolution remains challenging. Here, a sulfur host comprised of atomic cobalt-decorated hollow carbon nanospheres is synthesized to enhance sulfur reactivity and to electrocatalytically reduce polysulfide into the final product, sodium sulfide. The constructed sulfur cathode delivers an initial reversible capacity of 1081 mA h g −1 with 64.7% sulfur utilization rate; significantly, the cell retained a high reversible capacity of 508 mA h g −1 at 100 mA g −1 after 600 cycles. An excellent rate capability is achieved with an average capacity of 220.3 mA h g −1 at the high current density of 5 A g −1 . Moreover, the electrocatalytic effects of atomic cobalt are clearly evidenced by operando Raman spectroscopy, synchrotron X-ray diffraction, and density functional theory. Room-temperature sodium-sulfur batteries hold promise, but are hindered by low reversible capacity and fast capacity fade. Here the authors construct a multifunctional sulfur host comprised of cobalt-decorated carbon nanospheres that impart attractive performance as a cathode in a sodium sulfide battery.

Metal sulfides electrodeposition in sulfur cathodes mitigates the shuttle effect of polysulfides to achieve high Coulombic efficiency in secondary metal-sulfur batteries. However, fundamental understanding of metal sulfides electrodeposition and kinetics mechanism remains limited. Here using room-temperature sodium-sulfur cells as a model system, we report a Mo 5 N 6 cathode material that enables efficient Na 2 S electrodeposition to achieve an initial discharge capacity of 512 mAh g −1 at a specific current of 1 675 mA g −1 , and a final discharge capacity of 186 mAh g −1 after 10,000 cycles. Combined analyses from synchrotron-based spectroscopic characterizations, electrochemical kinetics measurements and density functional theory computations confirm that the high d -band position results in a low Na 2 S 2 dissociation free energy for Mo 5 N 6 . This promotes Na 2 S electrodeposition, and thereby favours long-term cell cycling performance. Incomplete conversion of sodium polysulfides represents a significant issue in room-temperature sodium-sulfur batteries. Here, the authors propose Mo 5 N 6 as an electrocatalyst for efficient Na 2 S electrodeposition and improved cell cycling performances.

Polysulfide dissolution and slow electrochemical kinetics of conversion reactions lead to low utilization of sulfur cathodes that inhibits further development of room-temperature sodium-sulfur batteries. Here we report a multifunctional sulfur host, NiS 2 nanocrystals implanted in nitrogen-doped porous carbon nanotubes, which is rationally designed to achieve high polysulfide immobilization and conversion. Attributable to the synergetic effect of physical confinement and chemical bonding, the high electronic conductivity of the matrix, closed porous structure, and polarized additives of the multifunctional sulfur host effectively immobilize polysulfides. Significantly, the electrocatalytic behaviors of the Lewis base matrix and the NiS 2 component are clearly evidenced by operando synchrotron X-ray diffraction and density functional theory with strong adsorption of polysulfides and high conversion of soluble polysulfides into insoluble Na 2 S 2 /Na 2 S. Thus, the as-obtained sulfur cathodes exhibit excellent performance in room-temperature Na/S batteries. Room temperature rechargeable sodium sulfur batteries are promising for next-generation energy storage systems, but their development is limited by polysulfide dissolution and slow kinetics. Here the authors report a cathode that serves as a multifunctional sulfur host and imparts enhanced performance.

Ensemble control has been intensively pursued for decades to identify sustainable alternatives to the Lindlar catalyst (PdPb/CaCO 3 ) applied for the partial hydrogenation of alkynes in industrial organic synthesis. Although the geometric and electronic requirements are known, a literature survey illustrates the difficulty of transferring this knowledge into an efficient and robust catalyst. Here, we report a simple treatment of palladium nanoparticles supported on graphitic carbon nitride with aqueous sodium sulfide, which directs the formation of a nanostructured Pd 3 S phase with controlled crystallographic orientation, exhibiting unparalleled performance in the semi-hydrogenation of alkynes in the liquid phase. The exceptional behavior is linked to the multifunctional role of sulfur. Apart from defining a structure integrating spatially-isolated palladium trimers, the active ensembles, the modifier imparts a bifunctional mechanism and weak binding of the organic intermediates. Similar metal trimers are also identified in Pd 4 S, evidencing the pervasiveness of these selective ensembles in supported palladium sulfides. Developing robust catalysts for alkyne semi-hydrogenation remains a challenge. Here, the authors introduce a scalable protocol to prepare crystal phase and orientation controlled Pd 3 S nanoparticles supported on carbon nitride, exhibiting unparalleled semi-hydrogenation performance due to a high density of active and selective ensembles.

The effect of sacrificial reagents (SRs) on photocatalytic H 2 evolution rate over different photocatalysts was systematically studied. Zn 0.5 Cd 0.5 S, graphitic carbon nitride (g-C 3 N 4 ), and TiO 2 were chosen as typical photocatalysts, while alcohols, amines, carboxylic acids, and inorganic Na 2 S/Na 2 SO 3 were chosen as SRs. The results indicate that Na 2 S/Na 2 SO 3 , methanol, and triethanolamine are the most suitable SRs for Zn 0.5 Cd 0.5 S, TiO 2 , and g-C 3 N 4 , respectively. It was found that in selecting organic SRs, both the permittivity and oxidation potential have profound effects on the H 2 production efficiency, which will provide basis for choosing appropriate SRs for different photocatalysts.