Search Results (172)

Supercapacitors are considered a bridge between batteries and capacitors due to their significant energy density, as well as power density. Herein, we prepared two novel electrodes of Fe_0.8Co_0.2S and Fe_0.8Co_0.2S/rGO composites and analyzed their supercapacitor performance. The results indicated that Fe_0.8Co_0.2S/rGO, prepared through co-precipitation and annealing, exhibited a higher specific capacitance value and improved electrochemical properties in comparison to Fe_0.8Co_0.2S due to the synergistic effect of rGO with Fe_0.8Co_0.2S. X-ray diffraction (XRD) confirmed the desired phases of Fe_0.8Co_0.2S, while scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) verified the microstructures and desired elements. Cyclic voltammetry (CV) confirmed an enhanced oxidation current from +25 mA to +49 mA at 10 mV/s, while galvanometric charge–discharge (GCD) showed an enhanced discharge time from 78 s to 300 s. As a result, the specific capacitance and energy density were enhanced from 74.3 F/g to 285.7 F/g and 2.84 Wh/kg to 10.9 Wh/kg, respectively. This contributed to a more than 283% increase in specific capacitance, as well as energy density. Overall, Fe_0.8Co_0.2S/rGO shows great potential for small-scale energy storage devices. Full article

Understanding how crystal structure influences electronic properties is crucial for discovering new functional materials. In this study, we utilized Kernel Principal Component Analysis (KPCA) to classify and analyze the Density of States (DOS) of transition metal sulfide (TMS) compounds, particularly copper-based sulfides. By mapping high-dimensional DOS data into a lower-dimensional space, we identify clusters corresponding to different crystal systems and detect outliers with significant deviations from their expected groups. These outliers exhibit unusual electronic configurations, suggesting potential applications in semiconductors, thermoelectric devices, and optoelectronic devices. Projected Density of States (PDOS) analysis further reveals how orbital hybridization governs the electronic structure of these materials, highlighting key differences between structurally similar compounds. Additionally, we analyze phase stability through inter-cluster distance measurements, identifying potential phase transformations between closely related structures. The implications for this work in terms of modifying chemistries and generalized DOS predictions are discussed. Full article

Carbon dioxide (CO₂) and hydrogen sulfide (H₂S) as harmful gases are always associated with methane (CH₄) in natural gas, biogas, and landfill gas. Given that chemisorption and physisorption are the key gas separation technologies in industry, selecting appropriate adsorbents is crucial to eliminate these harmful gases. The adsorption of CH₄, CO₂, and H₂S has been studied based on the density functional theory (DFT) in this work to evaluate the feasibility of transition metal (M = Mn, Fe, Co, Ni, Cu, Mo) porphyrin-like moieties embedded in graphene sheets (MN₄-GPs) as adsorbents. It was found that the interactions between gas molecules and MN₄-GPs (M = Mn, Fe, Co, Ni, Cu, Mo) are different. The weaker interactions between CH₄ and MN₄-GPs (M = Co, Ni, Cu, Mo) than those between CO₂ and MN₄-GPs or between H₂S and MN₄-GPs are beneficial to the separation of CH₄ from CO₂ and H₂S. The maximum difference in the interactions between gas molecules and MoN₄-GPs means that MoN₄-GPs have the greatest potential to become adsorbents. The different interfacial interactions are related to the amount of charge transfer, which could promote the formation of bonds between gas molecules and MN₄-GPs to effectively enhance the interfacial interactions. Full article

Metal sulfides are promising anode candidates for sodium–ion batteries (SIBs) due to their high theoretical capacities. However, their practical application is limited by significant volume extension and sluggish Na⁺ diffusion during cycling, which lead to rapid capacity degradation and poor long-term stability. In this work, we report the rational design of a hollow triple-shelled high-entropy sulfide (NaFeZnCoNiMn)₉S₈, synthesized through sequential templating method under hydrothermal conditions. Transmission electron microscopy confirms its well-defined three-shelled architecture. The inter-shell voids effectively buffer Na⁺ insertion/desertion-induced volume extension, while the tailored high-entropy matrix enhances electronic conductivity and accelerates Na⁺ transport. This synergistic design yields outstanding performance, including a high initial Coulombic efficiency (ICE) of 94.1% at 0.1 A g⁻¹, low charge-transfer resistance (0.32~2.54 Ω), fast Na⁺ diffusion efficiency (10^−8.5–10^−10.5 cm² s⁻¹), and reversible capacity of 582.6 mAh g⁻¹ after 1600 cycles at 1 A g⁻¹ with 91.2% capacity retention. These results demonstrate the potential of high-entropy, multi-shelled architectures as a robust platform for next-generation durable SIB anodes. Full article

Direct methanol fuel cells (DMFCs) represent a promising pathway for energy conversion, yet their reliance on platinum-group metal (PGM)-based anode catalysts poses critical sustainability challenges, which stem from finite mineral reserves, environmentally detrimental extraction processes, and prohibitive lifecycle costs. Current anode catalysts for DMFCs are dominated by platinum materials; therefore, this review systematically evaluates the following three emerging eco-efficient design paradigms using platinum materials as a starting point: (1) the atomic-level optimization of low-Pt alloy surfaces to maximize catalytic efficiency per metal atom, (2) Earth-abundant transition metal compounds (e.g., nitrides and sulfides) and coordination-tunable metal–organic frameworks as viable PGM-free alternatives, and (3) mechanically robust carbon architectures with engineered topological defects that enhance catalyst stability through covalent metal–carbon interactions. Through comparative analysis with pure Pt benchmarks, we critically examine how these strategic material innovations collectively mitigate CO intermediate poisoning risks and improve electrochemical durability. Such fundamental advances in catalyst design not only address immediate technical barriers, but also establish essential material foundations for the development of DMFC technologies compatible with circular economy frameworks and United Nations Sustainable Development Goal 7 targets. Full article

Zoharite (IMA 2017-049), (Ba,K)₆ (Fe,Cu,Ni)₂₅S₂₇, and gmalimite (IMA 2019-007), ideally K₆□Fe²⁺₂₄S₂₇, are two new sulfides of the djerfisherite group. They were discovered in an unusual gehlenite–wollastonite paralava with pyrrhotite nodules located in the Hatrurim pyrometamorphic complex, Negev Desert, Israel. Zoharite and gmalimite build grained aggregates confined to the peripheric parts of pyrrhotite nodules, where they associate with pentlandite, chalcopyrite, chalcocite, digenite, covellite, millerite, heazlewoodite, pyrite and rudashevskyite. The occurrence and associated minerals indicate that zoharite and gmalimite were formed at temperatures below 800 °C, when sulfides formed on external zones of the nodules have been reacting with residual silicate melt (paralava) locally enriched in Ba and K. Macroscopically, both minerals are bronze in color and have a dark-gray streak and metallic luster. They are brittle and have a conchoidal fracture. In reflected light, both minerals are optically isotropic and exhibit gray color with an olive tinge. The reflectance values for zoharite and gmalimite, respectively, at the standard COM wavelengths are: 22.2% and 21.5% at 470 nm, 25.1% and 24.6% at 546 nm, 26.3% and 25.9% at 589 nm, as well as 27.7% and 26.3% at 650 nm. The average hardness for zoharite and for gmalimite is approximately 3.5 of the Mohs hardness. Both minerals are isostructural with owensite, (Ba,Pb)₆(Cu,Fe,Ni)₂₅S₂₇. They crystallize in cubic space group Pm$\overline{3}$m with the unit-cell parameters a = 10.3137(1) Å for zoharite and a = 10.3486(1) Å for gmalimite. The calculated densities are 4.49 g·cm⁻³ for the zoharite and 3.79 g·cm⁻³ for the gmalimite. The primary structural units of these minerals are M₈S₁₄ clusters, composed of MS₄ tetrahedra surrounding a central MS₆ octahedron. The M site is occupied by transition metals such as Fe, Cu, and Ni. These clusters are further connected via the edges of the MS₄ tetrahedra, forming a close-packed cubic framework. The channels within this framework are filled by anion-centered polyhedra: SBa₉ in zoharite and SK₉ in gmalimite, respectively. In the M₈S₁₄ clusters, the M atoms are positioned so closely that their d orbitals can overlap, allowing the formation of metal–metal bonds. As a result, the transition metals in these clusters often adopt electron configurations that reflect additional electron density from their local bonding environment, similar to what is observed in pentlandite. Due to the presence of shared electrons in these metal–metal bonds, assigning fixed oxidation states—such as Fe²⁺/Fe³⁺ or Cu⁺/Cu²⁺—becomes challenging. Moreover, modeling the distribution of mixed-valence cations (Fe²⁺/³⁺, Cu⁺/²⁺, and Ni²⁺) across the two distinct M sites—one located in the MS₆ octahedron and the other in the MS₄ tetrahedra—often results in ambiguous outcomes. Consequently, it is difficult to define an idealized end-member formula for these minerals. Full article

Pursuing cost-effective non-precious metal electrocatalysts is a key challenge in the field of sustainable energy conversion. Transition metal dichalcogenides, known for their unique electronic structure, demonstrate superior electrocatalytic capabilities for the hydrogen evolution reaction (HER), yet their effectiveness is still lacking. In the present study, a CuS/Co₃S₄@MWCNT composite was fabricated via single-step hydrothermal synthesis for HER applications. This catalyst exploited the synergistic effects between CuS and Co₃S₄ to increase edge site functionalities and metallic conductivity, thereby resulting in high catalytical activity within the material. Furthermore, the incorporation of multi-walled carbon nanotubes (MWCNTs) into the composite effectively enhanced electron transfer kinetics throughout the HER process. Notably, thiourea serves a dual function in this synthesis, acting both as a reducing agent and as a sulfur source for the formation of metal sulfides. When evaluated in a 1 M KOH alkaline electrolyte, the synthesized nanocomposite exhibited a minimal overpotential of 300 mV to reach a current density of 10 mA/cm², and a Tafel slope of merely 76.2 mV/dec, indicative of its good HER catalytic activity. These findings underscore the composite’s potential for application in hydrogen production technologies. Full article

Hydrogen energy as a sustainable alternative to fossil fuels necessitates the development of cost-effective and efficient electrocatalysts for the hydrogen evolution reaction (HER). While transition metal sulfides have shown promise, their practical application is hindered by insufficient active sites, poor conductivity, and suboptimal hydrogen adsorption kinetics. Herein, we present a heterointerface engineering strategy to construct Co₉S₈/FeCoS₂ heterojunctions anchored on bamboo fiber-derived nitrogen-doped porous carbon (Co₉S₈/FeCoS₂/BFPC) through hydrothermal synthesis and subsequent carbonization. BFPC carbon quasi-aerogel support not only offers a high surface area and conductive pathways but also enables uniform dispersion of active sites through nitrogen doping, which simultaneously optimizes electron transfer and mass transport. Experimental results demonstrate exceptional HER performance in alkaline media, achieving a low overpotential of 86.6 mV at 10 mA cm⁻², a Tafel slope of 68.87 mV dec⁻¹, and remarkable stability over 73 h of continuous operation. This work highlights the dual advantages of heterointerface design and carbon substrate functionalization, providing a scalable template for developing noble metal-free electrocatalysts for energy conversion technologies. Full article

Modulating the oxidation states of transition metal species is a practical approach to enhance redox activity and increase the number of active sites in electrode materials. Herein, we describe a simple one-step hydrothermal approach to prepare Co_xS_y with two different phases, cobalt pyrite (CoS₂) and cobalt pentlandite (Co₉S₈), to explain the influence of material microstructure and properties on electrochemical performance. The as-prepared CoS₂ and Co₉S₈ were investigated as symmetric supercapacitor (SC) devices for potential energy storage applications. Co₉S₈ exhibited the highest specific gravimetric capacitance of 14.12 Fg⁻¹ at 0.2 mAcm⁻² with capacitance retention of 91.3% after 10,000 cycles, indicating robust cycling stability. In addition, the Co₉S₈ SC device showed the highest energy (E) and power (P) density of 9.14 Whkg⁻¹ and 0.23 kWkg⁻¹. These results highlight a simple approach of tailoring different phase syntheses of Co_xS_y structure toward high-performance electrode material for energy storage and conversion. Full article

¹³⁷Cs is a persistent β/γ-emitter (t_1/2 = 30.1 years) generated from ²³⁵U and ²³⁹Pu fission. It is a critical challenge to efficiently capture ¹³⁷Cs⁺ for nuclear waste management due to its high solubility, environmental mobility, and propensity for biological accumulation. Herein, we prepare a two-dimensional (2D) thiotitanate Rb_0.32TiS₂·0.75H₂O (denoted Rb-TiS₂) using a special molten salt synthesis method, “Mg + RbCl”. Rb-TiS₂ can selectively capture Cs⁺ from aqueous solutions. Its structure features a flexible anionic thiotitanate layer with Rb⁺ as counter ions located at the interlayer spaces. As an ion exchanger, it possesses high adsorption capacity (q_m^Cs = 232.70 mg·g⁻¹), rapid kinetics (the removal rate R > 72% within 10 min), and a wide pH tolerance range (pH = 4–12) for Cs⁺ adsorption. Through a single-crystal X-ray structural analysis, we elucidated the mechanism of Cs⁺ capture, revealing the ion exchange pathways between Cs⁺ and Rb⁺ in Rb-TiS₂. This work not only provides an important reference for the synthesis of transition metal sulfides with alkali metal cations but also proves the application prospect of transition metal sulfides in radionuclide remediation. Full article

Water electrolysis represents one of the most environmentally friendly methods for hydrogen production, while its overall efficiency is primarily governed by the electrocatalyst. Nickel sulfides, e.g., Ni₃S₂, are considered to be highly promising catalysts for the hydrogen evolution reaction (HER) due to their distinctive chemical structure. However, the practical application of Ni₃S₂-based electrocatalysts is hindered by unsatisfactory high overpotential in the HER and weakened catalytic performance under alkaline conditions. Therefore, in this regard, further research on Ni₃S₂-based catalysts is being carried out to tackle these challenges. This review provides a comprehensive survey of the latest advancements in Ni₃S₂-based in improving the HER performance of Ni₃S₂-based electrocatalysts. The review may offer some inspiration for the rational design and synthesis of novel transition metal-based catalysts with enhanced water electrolysis performance. Full article

Transition metal sulfide (TMS)-based electrocatalysts have received considerable attention in the field of sustainable energy, especially for their high activity in the hydrogen evolution reaction (HER). This review summarizes how researchers have improved the performance of TMSs by adjusting their composition. This review introduces the research background of transition metal sulfides and clarifies the reaction mechanism of the HER and its performance evaluation indicators. Then, it elaborates on the general synthesis techniques for preparing TMS materials, including hydrothermal methods, electrochemical deposition, liquid-phase exfoliation, chemical vapor deposition, and other methods. Moreover, it discusses the realization of excellent electrocatalytic performance in the HER through doping, hole treatment, heterostructures, and multi-sulfides. Finally, this review summarizes the current challenges and future development opportunities of TMS materials in the field of water electrolysis for hydrogen production. Full article

The results of a detailed examination of an anomalously PGM-rich anorthositic fragment from the Main Reef of the Yoko-Dovyren massif (Northern Transbaikalia, Russia) are presented. This fragment is to represent a 15 mm core drilled out from a typical low-sulfide PGE-rich anorthosite, occurring within the transition zone between troctolite and a rhythmically stratified sequence of olivine gabbro. Coupling multistage X-ray computed tomography (CT) with SEM studies allowed for revealing a heterogeneous distribution of PGMs and sulfides observable as (i) the main 4 mm sulfide globule containing some small PGMs around its periphery, with (ii) the bulk of the PGMs concentrated within a 3 mm sized scattered sulfide nest, comprising about 6 vol.% of the globule and located at a distance of 2–3 mm from it. Mass-balance calculations showed that the average sulfide composing this nest is 120fold richer in PGE than the sulfide globule. Calculations of sulfide minerals proportions showed that the globule consists of 39 vol.% Po, 21% Pn, 34% Cub, and 6% Ccp (consistent with 35.2 wt.% S, 48.2% Fe, 6.4% Ni, 9.9% Cu, and 0.4% Co), whereas the PGM-enriched sulfide domain includes (vol.%): Po—34, Pn—15, Ccp—23, and Cub—28 (respectively, S—35.2 wt.%, Fe—45.8%, Ni—4.6%, Cu—14.2%, and Co—0.3%). Thus, the PGM-enriched nest demonstrates an obvious increase in Cu relative to the sulfide globule. Further SEM studies of four thin sections of the globule and associated nest showed that they differ not only in the ratios of base metal sulfides, but also in the PGE mineralogy. The globule contains more high-temperature PGMs, such as moncheite, while the nest is enriched in “low-temperature” PGMs, including notable amounts of lead and mercury. The overwhelming majority of the numerous PGMs in the unusual domain were detected as tetraferroplatinum, with subordinate potarite and zvyagintsevite, associated with chlorite and apatite. Such a subdivision of anorthositic sulfides into two types demonstrating different composition and mineralogy, as well as contrasting distributions of PGE in the sulfide segregations, was established for the first time! The origin of the contrast PGM-sulfide assemblages is discussed. Full article

As an energy carrier characterized by its high energy density and eco-friendliness, hydrogen holds a pivotal position in energy transition. This paper elaborates on the scientific foundations and recent progress of photo- and electro-catalytic water splitting, including the corresponding mechanism, material design and optimization, and the economy of hydrogen production. It systematically reviews the research progress in photo(electro)catalytic materials, including oxides, sulfides, nitrides, noble metals, non-noble metal, and some novel photocatalysts and provides an in-depth analysis of strategies for optimizing these materials through material design, component adjustment, and surface modification. In particular, it is pointed out that nanostructure regulation, dimensional engineering, defect introduction, doping, alloying, and surface functionalization can remarkably improve the catalyst performance. The importance of adjusting reaction conditions, such as pH and the addition of sacrificial agents, to boost catalytic efficiency is also discussed, along with a comparison of the cost-effectiveness of different hydrogen production technologies. Despite the significant scientific advancements made in photo(electro)catalytic water splitting technology, this paper also highlights the challenges faced by this field, including the development of more efficient and stable photo(electro)catalysts, the improvement of system energy conversion efficiency, cost reduction, the promotion of technology industrialization, and addressing environmental issues. Full article

Electrochemical water splitting provides a sustainable method for hydrogen production. However, the primary challenge for electrochemical hydrogen generation is the high cost and limited availability of platinum-based noble-metal catalysts. Transition-metal chalcogenides have been identified as low-cost and efficient electrocatalysts to promote the hydrogen evolution reaction (HER) in alkaline electrolytes. Nonetheless, the identification of active sites and the underlying catalytic mechanism remain elusive. In this study, phosphorus-doped nickel sulfide has been successfully synthesized, demonstrating enhanced activity for alkaline HER. Investigating surface chemistry through X-ray photoelectron spectroscopy (XPS), depth profiling revealed that surface restructuring occurs during the HER process. The presence of phosphorus significantly influences this transformation, promoting the formation of a novel active Ni-O layer. This Ni-O layer is responsible for enhanced catalytic activity by upshifting the d-band center and increasing the density of states near the Fermi level, along with expanding the electrochemical surface area. This study reveals that the surface restructuring of transition-metal sulfides is highly tied to the electronic structure of the parent catalysts. Gaining a comprehensive understanding of this surface restructuring is essential for predicting and exploring more efficient non-precious transition-metal sulfide electrocatalysts. Full article