Sulfur Defects Research Articles

Growth and stabilization of high-concentration metallic 1T-phase MoS2 as a high-performance l-cysteine electrochemical sensor by electron injection engineering

MoS2 is an attractive electrochemical sensing electrode material for the detection of biomolecule because of its adjustable band gap, large surface area, and unique electrochemical characteristics. However, the poor catalytic and electrical conductivity of the semiconductor 2H-phase MoS2 and the phenomenon of restacking during electrochemical use hinder its sensing application. Herein, electron injection engineering is employed for the formation and stabilization of high-concentration metal 1T-phase MoS2 nanosheets on ionic liquid-functionalized carbon nanotubes (CNTs-IL). The increase of MoS2 concentration in the metal 1T phase significantly accelerates electron transfer kinetics. The in-situ growth method results in a tightly interfaced coupling effect, thereby substantially shortening the electron transport pathway and decreasing interfacial transmission impedance. In addition, the sulfur defects on the surface of MoS2 as the anchoring point of sulfhydryl groups promote the enrichment of thiols on the surface of the material and reduce the reaction barrier for sulfhydryl oxidation, thereby improving the catalytic performance. The prepared CNTs-IL-MoS2/SPE biosensor shows excellent l-cysteine sensing performance by electrochemical detection.

Insights into the Effect of Crystal Facets and Sulfur Defects on the Product Selectivity of Various CdS Configurations for CO2 Photoreduction: A DFT Study

CO2 photoreduction into valuable hydrocarbons, such as CO, CH4, and C2H4, delivers a promising approach to address both environmental and energy challenges. Transition metal chalcogenides, particularly cadmium sulfide (CdS), have emerged as prominent candidates due to their tunable electronic properties and availability. This study delves into a comprehensive investigation of how CdS crystalline facets and sulfur-deficient surfaces modulate the product selectivity. Through employing density functional theory (DFT), we unravel the catalytic performance of various CdS crystal orientations and sulfur vacancy configurations. The results have shown that different CdS facets exhibit unique electronic characteristics and surface energetics, which influence the adsorption dynamics and reaction pathways. The introduction of sulfur vacancies further modulates the nature of active sites, leading to substantial shifts in product selectivity. A detailed investigation on the reaction mechanisms unveils that specific facets preferentially facilitate the formation of CO, while others are more conducive to the generation of hydrocarbons such as CH4 and C2H4, due to the variations in activation barriers and intermediate stabilities. These findings underscore the importance of crystal facet engineering and defect manipulation in tailoring catalyst performance thus providing valuable insights for the rational design of efficient and selective CO2 reduction metal catalysts.

Surfactants govern the fabrication of sulfur-enriched heterojunction catalysts for highly selective photocatalytic conversion of toluene

Photocatalytic selective oxidation of toluene represents a milder and more environmentally friendly strategy for the synthesis of benzaldehyde. In order to enhance catalytic performance, efficient carrier separation and transport are crucial in the photocatalytic process. This study focused on the preparation of ZnS@ZnIn2S4 with sulfur vacancies and heterostructures, combining the advantages properties of ZnS and ZnIn2S4 in photocatalysis. The effects of ZnS and surfactants on the catalytic properties of the composites were studied in depth. Characterization tests revealed that surfactant-modified ZnS@ZnIn2S4 exhibited a higher concentration of sulfur defects, which facilitated electron trapping and promoted photogenerated carrier separation and utilization. Additionally, the present study also demonstrated that the incorporation of ZnS and surfactants could reduce the crystal size of ZnIn2S4, thereby facilitating the exposure of additional active sites. The synergistic effect of the aforementioned advantages enabled toluene to undergo oxidation at a conversion rate of 39% in the presence of oxygen, resulting in the production of benzaldehyde with an exceptional selectivity of 92%. This finding offers valuable insights for future endeavors in designing photocatalytic C-H bond oxidation catalysts.

Tunable sulfur vacancies in amorphous-crystalline AC-Bi2S3-x@C derived from CAU-17 for efficient capture of radioiodine: Comparison of sulfur vacancies in amorphous and crystalline structures

Solid-phase adsorption has been recognized as an effective method for the control of volatile radioactive iodine in spent fuel reprocessing plant off-gases. However, it is still a challenge to develop efficient and stable iodine capture adsorbents. In this work, sulfur-vacancy-rich amorphous-crystalline AC-Bi2S3-x@C was prepared by solvothermal vulcanization using CAU-17 as a precursor. Based on the synergistic effect of the amorphous structure and sulfur vacancy defects, AC-Bi2S3-x@C exhibited fast adsorption equilibrium time (15 min), distinguished iodine adsorption capacity (1763.9 mg g−1), high percentage of chemical adsorption (93.4 %) as well as favorable thermal and irradiation stability. Adsorption experiments and theoretical calculations verified that the amorphous structure not only enhance the charge transfer between sulfur vacancy defects and iodine molecules, but also offers rapid diffusion channels for iodine molecules to the interior of the adsorbent and sufficient internal binding sites to promote iodine molecule adsorption in its interior. The used adsorbent showed high iodine retention (92.3 %) and excellent chemical durability (normalized iodine leaching rate of 4.63 × 10-5 g m−2 d-1) in glass solidification. In general, this work presented a new concept in the design and synthesis of efficient radioactive iodine capture materials.

Low-Defect-Density Monolayer MoS2 Wafer by Oxygen-Assisted Growth-Repair Strategy.

Atomic chalcogen vacancy is the most commonly observed defect category in two dimensional (2D) transition-metal dichalcogenides, which can be detrimental to the intrinsic properties and device performance. Here a low-defect density, high-uniform, wafer-scale single crystal epitaxial technology by in situ oxygen-incorporated "growth-repair" strategy is reported. For the first time, the oxygen-repairing efficiency on MoS2 monolayers at atomic scale is quantitatively evaluated. The sulfur defect density is greatly reduced from (2.71 ± 0.65) × 1013 down to (4.28 ± 0.27) × 1012 cm-2, which is one order of magnitude lower than reported as-grown MoS2. Such prominent defect deduction is owing to the kinetically more favorable configuration of oxygen substitution and an increase in sulfur vacancy formation energy around oxygen-incorporated sites by the first-principle calculations. Furthermore, the sulfur vacancies induced donor defect states is largely eliminated confirmed by quenched defect-related emission. The devices exhibit improved carrier mobility by more than three times up to 65.2 cm2 V-1 s-1 and lower Schottky barrier height reduced by half (less than 20 meV), originating from the suppressed Fermi-level pinning effect from disorder-induced gap state. The work provides aneffective route toward engineering the intrinsic defect density and electronic states through modulating synthesis kinetics of 2D materials.

Sulfur defect engineering boosted nitrogen activation over FeS2 for efficient electrosynthesis of ammonia

Electrocatalytic nitrogen (N2) reduction to ammonia (NH3) reaction (eNRR) supplies a promising alternative to the Haber-Bosch technology. However, the dissociation of NN bond hinders its development. Herein, sulfur vacancies are introduced into FeS2 for promoting N2 activation and thus stimulating the eNRR progress. Experimental investigations and density functional theory (DFT) calculations reveal that the electrons could transfer from Fe 3d orbits to N2 2π* orbital, thus facilitating the cracking of inert N2 molecules. And the electron transfer is easier for those Fe atoms with S vacancies in adjacent positions. Furthermore, we find that eNRR process on the FeS2 surface follows the distal and alternating hybrid pathway. Also, the water molecules in the electrolyte facilitate the first hydrogenation of N2 (*N2 → *NNH). Notably, FeS2 with rich sulfur vacancies exhibits an excellent NH3 yield rate of 67.5 μg h−1 mgcat.−1, which outperforms most of the reported eNRR activities of Fe-based catalysts.

Sulfur vacancy riched pure 2H phase VS2 for efficient electrocatalytic hydrogen evolution

Vanadium disulfide (VS2), a typical metallic layered transition metal chalcogenide (TMC), has been widely concerned for its high electrical conductivity and reactivity in electrochemical energy storage and conversion applications. The 2H phase VS2 is expected to exhibit high electrocatalytic activity and be more stable for hydrogen evolution reaction (HER) than the 1T phase structure. But at present, there still lacks a facile method to prepare pure 2H phase VS2. Herein, we successfully prepared pure 2H–VS2 through a simple one-step low-temperature hydrothermal method. We have investigated the effect of the hydrothermal reaction conditions (including the proportion of raw materials and hydrothermal reaction temperatures) on the phase composition and microstructure. Under the optimal condition of 140°C-24 h with a vanadium sulfur ratio of 1:5, a nano-flower-like 2H–VS2 material with high crystallinity and rich sulfur vacancy defects was obtained. Leveraging these structural advantages, as a demonstration, the product exhibits excellent electrocatalytic HER activity (with η10 of 181 mV, Tafel slope of 52 mV dec−1, and J0 of 67.9 × 10−3 mA cm−2) and stability (it can continuously produce hydrogen for 20 h at a current density of 50 mA cm−2 with ultra-small increased potential of less than 5 mV). This work provides a new way for constructing atomic vacancy defects in layered TMCs for efficient electrocatalysis and is also expected to promote the research of the basic properties of high phase purity TMCs.

Unveiling Negative Differential Resistance and Superionic Conductivity: Water Anchored on Layered Materials.

Unravelling the perplexing nature of negative differential resistance (NDR) in 2D transition metal dichalcogenide (2D TMD) devices, especially regarding intrinsic properties, is hindered by experiments conducted in ambient environments. A thorough investigation is essential for unveiling the actual mechanism. In this study, we provide compelling evidence of the NDR effect with a remarkably high peak-to-valley current ratio and proton-diffused superionic conductivity in quantum-confined water molecules anchored to a thin film of 2D TMDs. Our investigation underscores the crucial role of ambient moisture for this robust NDR effect independent of underlying materials used. The bonding of water molecules to the existing sulfur defect sites on 2D TMD nanoflakes facilitates the formation of bridges between two planar metal electrodes, thus enabling superionic in-plane protonic conduction. During electrolysis of chemisorbed water, protons are liberated at the anode and migrate toward the cathode during bias voltage sweeping. Nevertheless, proton diffusion encounters increasing impedance beyond a certain applied bias, thereby restricting current flow even with higher biasing voltages, which is attributed to the interfacial Schottky energy barrier influenced by the Fermi level pinning effect. Our DFT simulations corroborate this mechanism, revealing minimal intermolecular interaction of H+ ions compared to OH- ions at distinct atomic sites on 2D TMD nanoflakes.

Enhanced nitrogen electroreduction to ammonia activities on Sb2S3 electrocatalyst by sulfur defects coupled with carbon doping

Exploiting effective, robust while cheap catalysts for the nitrogen reduction reaction (NRR) is of great significance in the scalability and renewability of electrochemical NH3 synthesis. Herein, a synergetic strategy of C dopants and S vacancies was employed into Sb2S3 (marked as C-Sb2S3-x) to boost the electrochemical NRR performance. The induced effects of C dopants and S vacancies of Sb2S3 on the physical and electrochemical behaviors were throughly investigated. Experiments verify that, the content of low oxidation state in Sb species are remarkably enhanced after introducing C dopants and S vacancies, this facilitate the enhanced electric conductivity and NRR activities of C-Sb2S3-x, together with the encouraged reaction kinetics. The prepared C-Sb2S3-x delivered an optimized NH3 yield rate of 47.2 μg h−1 mg−1cat. at −0.6 V along with a high Faradaic efficiency value of 6.4 % at −0.5 V in acid, outperforming than those of Sb2S3 and most disclosed sulfid NRR electrocatalysts. Density functional theory calculations validate that, cooperation of C doping and S vacancy could achieve the elevated NH3 yield rate, Faradaic efficiency as well as competitive stability. This approach puts forward an effective strategy for transition metal compounds to be more suitable for efficient electrocatalysis.

Sodium-assisted MoS2 for boosting CO2 hydrogenation to methanol: The crucial role of sodium in defect evolution and modification

The effective conversion of CO2 to methanol utilizing green hydrogen under moderate conditions represents a promising approach for achieving carbon neutrality. MoS2 demonstrates exceptional catalytic performance at temperatures below 200 °C, however, generating in-plane sulfur defects is challenging due to the intact planar structure. Introducing heteroatoms to induce sulfur vacancy formation and modulate their chemical environment remains a significant obstacle. In this study, we developed a NaCl-assisted method for synthesizing MoS2 and discovered that a small quantity of sodium not only promotes the formation of sulfur vacancies during the induction period, but also encourages CO2 hydrogenation via the carboxylate route, as opposed to the CO2 dissociation to CO* route over non-modified sulfur vacancies. Furthermore, catalysts at various stages throughout the 60 h induction period were characterized, revealing that the increase in sulfur vacancies and enhanced H2 dissociation capability are primary factors contributing to improved methanol yield. The sodium-modified MoS2 achieves a methanol space–time yield of up to 571 mgMeOH gcat.−1 h−1 at 200 °C and 5 MPa with a 4.8% CO2 conversion and 96% methanol selectivity. The turnover frequency based on total sulfur vacancies reaches 170 h−1. This research is anticipated to offer a new strategy for enhancing the catalytic performance of CO2 hydrogenation to methanol using heteroatom-assisted defect engineering.

Synergistic Hydrogen Peroxide‐Driven Cation Valence Regulation and La/O Co‐Doped SnS‐Based Oxysulfide Catalyst for Efficient Catalytic Reduction of Toxic Organics and Cr(VI) Under Dark

AbstractA novel La/O co‐doped SnS oxysulfide catalyst (labeled SnLaOS) with heterovalent tin states and sulfur vacancy defects is successfully synthesized for effective catalytic reduction of toxic organics heavy metal ions with NaBH4 in the dark. La/O co‐doped and hydrogen peroxide‐driven SnLaOS catalyst with suitable heterovalent Sn2+/Sn4+ states and sulfur vacancy defects exhibited excellent catalytic reduction capability. The 100 mL 20 ppm of 4‐nitrophenol (4‐NP) and 50 ppm of rhodamine‐B (RhB), methylene blue (MB), methyl orange (MO), and Cr(VI) solution are entirely reduced by 5 mg SnLaOS‐3 within 10, 12, 12, 16, and 14 min, respectively, with durable stability. Synergistic transition metal La3+‐cation and O2−‐anion co‐doped SnS adjusted the energy bandgap and introduced sulfur vacancy defects, and the hydrogen peroxide‐driven regulated the SnLaOS with suitable Sn4+/Sn2+ states ratio. The sulfur vacancies in SnLaOS provide active sites for adsorbed proton for pollutants reduction, and heterovalent Sn2+/Sn4+ states in SnLaOS facilitates electrons efficient transfer through electron hopping between Sn2+ and Sn4+ for pollutants reduction. This study provides a novel efficient catalyst for the water pollutants treatment.

Cu-In Dual Sites with Sulfur Defects toward Superior Ethanol Electrosynthesis from CO2 Electrolysis.

The electrosynthesis of multi-carbon chemicals from excess carbon dioxide (CO2) is an area of great interest for research and commercial applications. However, improving both the yield of CO2-to-ethanol conversion and the stability of the catalyst at the same time is proving to be a challenging issue. Here it is proposed to stabilize active Cu(I) and In dual sites with sulfur defects through an electro-driven intercalation strategy, which leads to the delocalization of electron density that enhances orbital hybridizations between the Cu-C and In-H bonds. Hence, the energy barrier for the rate-limiting *CHO formation step is reduced toward the key *OCHCHO* formation during ethanol production, which is also facilitated by the combined Cu site enabling C-C coupling and In site with a higher oxygen affinity based on both thermodynamic and kinetic calculations. Accordingly, such dual-site catalyst achieves a high partial current density toward ethanol of 409 ± 15mAcm⁻2 for over 120 h. Furthermore, a scaled-up flow cell is assembled with an industrial-relevant current of 5.7 A for over 36 h, in which the carbon loss is less than 2.5% and single-pass carbon efficiency is ≈19%.

Construction of novel S-defects rich ZnCdS nanoparticles for synergistic visible light assisted photocatalytic degradation of rhodamine B: Insights into mechanism, pathway and by-products toxicity evaluation

The contamination of wastewater by azo dyes indicates serious environmental risks. Currently, industries worldwide use approximately 700,000 tons of these dyes annually, making their removal a significant challenge. In photocatalysis research, a prominent area of dedication to the advancement of visible light photocatalysis aims to achieve superior performance in overall activity. In this study, we fabricated ZnCdS nanoparticles (NPs) via a simple co-precipitation strategy, and sulphur (S)-defect-rich ZnCdS NPs (D-ZnCdS) were created through the ball milling method. These S-defect nanoparticle (NPs) catalysts were utilized for rhodamine B (RhB) dye photocatalytic degradation experiment. (XRD) X-ray diffractometer, X-ray photoelectron spectroscopy (XPS), surface-enhanced Raman spectroscopy, and photoluminescence (PL) spectroscopy characterization studies explained the induced S-defect rich in D-ZnCdS NPs. Further, the morphological, band gap determination, and photogenerated charge carrier recombination efficiency were studied using different analytical and spectroscopic characterization techniques. The Brunauer-emmett-teller (BET) results indicate the increased surface area of D-ZnCdS NPs thereby providing more active sites. The photocatalytic degrading efficiency of D-ZnCdS over RhB explains the complete degradation of pollutants within 260 min. This enhancement in the catalytic process is attributed to the increased absorption of photon energy from the visible light and large defect-rich active sites. Further, the involvement of hydroxyl (*OH) and superoxide radicals (O2*-) in the degradation of RhB along with the presence of sulphur defects, significantly improves the charge transfer in ZnCdS NPs. The involvement of certain factors like pH, ions, NCs catalyst and different RhB concentrations on RhB degradation was investigated. Additionally, D-ZnCdS NPs showed stable degrading capability even after six consecutive cycles of catalytic RhB degradation. The by products formed during the RhB photodegradation experiment were identified using Gas chromatography-mass spectrometer (GC-MS) analysis, and toxicity in fish, daphnia, and algae was examined using the Ecological structure-activity relationships (ECOSAR) program. From the above findings, the current research work provides a new strategy for utilizing defect-engineered D-ZnCdS NPs as a promising catalyst for various environmental remediation applications and paves a ways for manufacturing innovation.

Sulfur vacancy-induced 1T-MoS2 co-catalyst loaded on Zn3In2S6 for simultaneous promoting photocatalytic hydrogen evolution and pollutant degradation

In the field of photocatalytic hydrogen evolution, Zn3In2S6 has caught tremendous attention because of its suitable band gap and outstanding stability. However, the lower number of active sites as well as lower efficiency of photoproduced carrier separation restricted its further application. Introducing co-catalysts and structural defects are effective methods to solve the above problems. In this paper, Zn3In2S6 loaded metal phase MoS2 to construct flower-shaped spherical catalysts 1T-MoS2/Zn3In2S6 (M/ZIS6) with abundant sulfur vacancies. The visible-light-driven photocatalytic hydrogen evolution rate of 2.4 % M/ZIS6 was 8.71 mmol∙g−1·h−1, which far exceeded those of pure Zn3In2S6 (0.80 mmol∙g−1·h−1) and 2.4 % Pt/Zn3In2S6 (3.86 mmol∙g−1·h−1). Moreover, 2.4 % M/ZIS6 simultaneously displayed the excellent photocatalytic degradation performance toward acid orange 7 (AO7) in the hydrogen evolution reaction process. Co-catalyst metal phase 1T -MoS2, abundant sulfur defects, and a large and dense contact interface between 1T -MoS2 and Zn3In2S6 mainly contributed to the enhanced photocatalytic performance of 2.4 % M/ZIS6. This work provided a potential concept to construct efficient photocatalysts with noble metal-free co-catalyst for bifunctional applications.

Impact of crystallinity on thermal conductivity of RF magnetron sputtered MoS2 thin films

This study investigates the effects of sulfur atomic defects and crystallinity on the thermal conductivity of MoS2 thin films. Utilizing scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), and Raman spectroscopy, we examined MoS2 films, several nanometers thick, deposited on Si/SiO2 substrates. These films were prepared via a combination of RF magnetron sputtering and sulfur vapor annealing (SVA) treatment. Structural analyses, including cross-sectional STEM and in-plane and out-of-plane XRD measurements, revealed an increase in the S/Mo ratio and grain size of the MoS2 films following SVA treatment. Notably, the in-plane thermal conductivity of MoS2 films treated with SVA was found to be at least an order of magnitude higher than that of films without SVA treatment. This research suggests that the in-plane thermal conductivity of MoS2 thin films can be significantly enhanced through crystallinity improvement via SVA treatment.

Improvements of multifunctional spintronic and optoelectronic applications of nanostructured Eu-doped ZnS thin films through magnetic and linear, nonlinear optical investigations

This study describes the spintronic and optoelectronic improvements upon Eu substitution in Zn atomic site of the nanostructure ZnS thin films. The electron beam deposition technique has been used to deposit a series of Zn1-xEuxS thin films on a glass substrate with different Eu dopants (x = 0, 0.01, 0.03, 0.05, and 0.08). The nanostructure nature of the Eu-doped ZnS thin film has been confirmed from structural and morphology studies performed by the X-ray diffraction (XRD) and atomic force microscope (AFM) measurements. XRD investigations further show a hexagonal-type structure with no detectable extra phases with the lattice parameter c increasing, while a decrease linearly with increasing Eu-dopant in the ZnS hosted lattice. The microstructures analysis reveals a reduction in the mean crystallite size and increasing in the lattice strain of the films with rising Eu doping. The Fourier transform infrared spectra display the existence of chemical bonds in the thin films whereas photoluminescence reveals near-band edge emission. The linear optical parameters were obtained from the analysis of the transmission data measured by the spectrophotometer technique. The results reveal that the band gap energy (EgOpt) reduces by raising ohe Eu doping ratio, which is ascribed to the structural deformation (strain and/or defects) confirmed from structural analysis, density of localized states and PL measurements. The index of refraction n was calculated using the Swanepoel method. The values were found to increase as the level of Eu doping grows, which is associated with the rise in polarizability. Wemple and DiDomenico's (WDD) model was utilized to compute the dispersive and oscillator energies (Eo, and Ed), the nonlinear absorption coefficient βc, nonlinear refractive index n2, and nonlinear optical susceptibility χ3. The results demonstrate that the adjustability of EgOpt , Eo, and Ed of ZnS: Eu films is conducted to improve the nonlinear optical characteristics, providing it well-suited for optoelectronic device implementations. On the other hand, ZnS doped with Eu film displays inherent ferromagnetic properties at room temperature, as evidenced by the results of the magnetic investigation. This finding could be attributed to the presence of sulphur defects (vacancies), as supported by photoluminescence (PL) measurements, which lead to the creation of the bound magnetic polaron. These discoveries indicate the potential of utilizing Eu-doped ZnS film in the effective development of spintronic devices.

Modification of mono-layer MoS2 through post-deposition treatment and oxidation for enhanced optoelectronic properties

Precise control of the optical and electrical properties of mono-layer (ML) thin MoS2 is crucial for future applications in functional devices. Depending on the synthesis route and the post-deposition annealing protocols, the number of sulfur vacancies in the material is different, which has a profound impact on the properties of the 2D layer. Here, we show that the sulfur vacancy-rich ML MoS2 films oxidize already at room temperature, which changes the photoluminescence (PL) yield, the MoS2–Al2O3 substrate interaction, and the structural integrity of the films. We used x-ray photoelectron spectroscopy to monitor the formation of MoO3 and possibly MoS3−xOx after exposure to air and to quantify the number of sulfur defects in the films. Atomic force microscopy measurements allow us to pinpoint the exact regions of oxidation and develop a dedicated low temperature heating procedure to remove oxidized species, leading to MoO3-free MoS2 films. AFM and Kelvin probe force microscopy show that the MoS2–Al2O3 substrate coupling is changed. The reduction in the MoS2–substrate coupling, combined with a preferential oxidation of sulfur vacancies, leads to a sevenfold increase in the PL intensity, and the ratio between trions and neutral excitons is changed. Our work highlights the importance of oxidized sulfur vacancies and provides useful methods to measure and manipulate their number in MoS2. Furthermore, changes in the MoS2–substrate interaction via sulfur vacancies and oxidation offer an elegant pathway to tune the optoelectronic properties of the two-dimensional films.

Sulfur-Defect-Induced TiS1.94 as a High-Capacity and Long-Life Anode Material for Zinc-Ion Batteries.

Aqueous zinc-ion batteries (ZIBs) are competitive among the elective candidates for electrochemical energy storage systems, but the intrinsic drawbacks of zinc metal anodes such as dendrites and corrosion severely hinder their large-scale application. Developing alternative anode materials capable of high reversibility and stability for storing Zn2+ ions is a feasible approach to circumvent the challenge. Herein, a sulfur-defect-induced TiS1.94 (D-TiS1.94) as a promising intercalation anode material for ZIBs is designed. The abundant Zn2+-storage active sites and lower Zn2+ migration barrier induced by sulfur defects endow D-TiS1.94 with a high capacity for Zn2+-storage (219.1 mA h g-1 at 0.05 A g-1) and outstanding rate capability (107.3 mA h g-1 at 5 A g-1). In addition, a slight volume change of 8.1% is identified upon Zn2+ storage, which favors a prolonged cycling life (50.3% capacity remaining in 1500 cycles). More significantly, the D-TiS1.94||ZnxMnO2 full battery demonstrates a high discharge capacity of 155.7 mA h g-1 with a capacity retention of 59.8% in 400 cycles. It has been estimated that the high-capacity, low-operation voltage, and long-life D-TiS1.94 can be a promising component of the ZIB anode material family, and the strategy proposed in this work will provide guidance to the defect engineering of high-performance electrode materials toward energy storage applications.

Unraveling high efficiency multi-step sodium storage and bidirectional redox kinetics synergy mechanism of cobalt-doping vanadium disulfide anode

Sodium-based storage devices based on conversion-type metal sulfide anodes have attracted great attention due to their multivalent ion redox reaction ability. However, they also suffer from sodium polysulfides (NaPSs) shuttling problems during the sluggish Na+ redox process, leading to “voltage failure” and rapid capacity decay. Herein, a metal cobalt-doping vanadium disulfide (Co-VS2) is proposed to simultaneously accelerate the electrochemical reaction of VS2 and enhance the bidirectional redox of soluble NaPSs. It is found that the strong adsorption of NaPSs by V-Co alloy nanoparticles formed in situ during the conversion reaction of Co-VS2 can effectively inhibit the dissolution and shuttle of NaPSs, and thermodynamically reduce the formation energy barrier of the reaction path to effectively drive the complete conversion reaction, while the metal transition of Co elements enhances reconversion kinetics to achieve high reversibility. Moreover, Co-VS2 also produce abundant sulfur vacancies and unsaturated sulfur edge defects, significantly improve ionic/electron diffusion kinetics. Therefore, the Co-VS2 anode exhibits ultrahigh rate capability (562 mA h g−1 at 5 A g−1), high initial coulombic efficiency (≈90%) and 12,000 ultralong cycle life with capacity retention of 90% in sodium-ion batteries (SIBs), as well as impressive energy/power density (118 Wh kg−1/31,250 W kg−1) and over 10,000 stable cycles in sodium-ion hybrid capacitors (SIHCs). Moreover, the pouch cell-type SIHC displays a high-energy density of 102 Wh kg−1 and exceed 600 stable cycles. This work deepens the understanding of the electrochemical reaction mechanism of conversion-type metal sulfide anodes and provides a valuable solution to the shuttling of NaPSs in SIBs and SIHCs.

Coordination engineering of the interfacial chemical bond and sulfur vacancies modulated S‐scheme charge transfer for efficient photocatalytic CO2 reduction

Surface charge localization and poor carrier separation efficiency limited the of photocatalytic CO2 reduction (PCR) activity. Creating heterojunctions between the interfacial layers was an important strategy used to enhance catalytic activity. Here, a core-shell structure S-scheme catalyst was constructed by growing of Bi2WO6 (BWO) nanospheres on the surface of Zn0.5Cd0.5S(VS-ZCS) nanospheres with abundant sulfur defect, and which was coordinated by the interface bonding and the sulfur vacancies (VS) for efficient PCR. Meanwhile, the surface potential was 91 mV, indicating the creation of strong interface electric field (IEF). As part of the strong synergy of the Bi-S bond, IEF and VS, the improved photocatalyst exhibited high CO evolution rate of 86.16 μmol⋅g−1, which was about 9.23 fold of the pristine VS-ZCS. This was attributed to production of *COOH intermediates on the VS-ZCS/BWO surface that had been proved to be crucial for PCR generation CO. Besides, electrons quickly migrated through the formed Bi-S bonds to the catalytic sites, accelerating charge separation. The use of VS as electron traps was beneficial for regulating the localization of photogenerated charges on the surface of S-scheme heterostructure. The Bi-S bonds and VS modulated S‐scheme charge transfer for efficient photocatalytic CO2 reduction provides new insights into photocatalytic CO2 reduction.