Partial Sulfidation Research Articles

Distinctive 3D heterostructures of partial sulfidation with FeCo LDH: A potent electrocatalyst for synergistic alkaline overall water splitting

The reasonable surface engineering allows effective modification of the adsorption energy of reactive hydrogen molecules, resulting in the improvement of the effectiveness of water separation. Herein, we fabricated MoS2-FeCoS2-FeCo LDH/NF (defined as: MS-FCS-FCL/NF) sea urchin-like nanospike sphere catalysts with heterogeneous interfaces by a simple two-step hydrothermal method and simultaneous sulfurisation of FeCo LDH for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which optimised the electronic structure and exposed more active sites, thus revealing excellent electrocatalytic performance. As predicted, the synthesized 3D "sea urchin-like" structure MS-FCS-FCL/NF has excellent HER (η10 = 176 mV) and OER (η10 = 149 mV) properties. Remarkably, when used as a bifunctional catalyst to perform overall water decomposition, it requires just a low cell voltage (1.53 V for 10 mA cm−2) and has outstanding stability (48 h). Density functional theory (DFT) calculations have proven that tuning electron dissipation and aggregation at heterogeneous interfaces can optimize the electron transfer rate in the active sites and D-band centers near the Fermi level and enhance the inherent catalytic activity. This work provides both an elegant method for building hierarchical heterostructures and a multiscale strategy for water separation electrocatalyst.

Construction of CoO/Co9S8/NC composites with low-frequency and broadband electromagnetic wave absorption

Low-frequency electromagnetic wave absorption (EMWA) materials were crucial for addressing electromagnetic pollution and radar stealth. However, achieving low-frequency and broadband absorption still faces challenges. In this work, a succession of CoO/Co9S8/N-doped carbon (NC) composites were fabricated via a partial sulfidation strategy of Co-Prussian blue analogue (Co-PBA). The as-prepared CoO/Co9S8/NC composites featured a porous architecture. The electromagnetic parameters were effectively modulated via varying the sulfidation time. When the sulfidation time was 9 h, the minimum reflection loss (RLmin) value was −50.40 dB at 2.93 mm and a maximum effective absorption bandwidth value was 5.76 GHz (12.24–18.00 GHz) at 1.80 mm. Notably, when the sulfidation time was 12 h, the composites exhibited enhanced EMWA capability in the low-frequency S-band (3.52 GHz) with an RLmin value of −28.91 dB. The superior EMWA performance of composites were primarily attributed to appropriate dielectric constants and optimized impedance matching due to magnetic loss. Moreover, the radar cross section simulation consequences further verified that dissipation capability of electromagnetic wave of the CoO/Co9S8/NC composites in the actual far field. This work afforded novel perspectives into the rational develop of PBA-derived carbon-based EMWA materials with the low-frequency and broadband absorption.

Interface engineering of 2D NiFe LDH/NiFeS heterostructure for highly efficient 5-hydroxymethylfurfural electrooxidation

The electrochemical oxidation of 5-hydroxymethylfurfural (HMF) to valuable chemicals is an efficient way to upgrade biomass molecules and replace traditional catalytic synthesis. It is crucial to develop efficient and low-cost earth-abundant electrocatalysts to enhance catalytic performance of HMF oxidation. Herein, a new type of two-dimensional (2D) hybrid arrays consisting of NiFe layered double hydroxides (LDH) nanosheets and bimetallic sulfide (NiFeS) is constructed via interface engineering for efficient electrocatalytic oxidation of HMF to 2,5-furandicarboxylic acid (FDCA). The preparation process of 2D NiFe LDH/NiFeS with ultrathin heterostructure involves in anchoring a Co-based metal-organic framework (Co MOF) as template onto the carbon cloth (CC) via in-situ growth, formation of NiFe LDH on the surface of Co MOF and subsequent partial sulfidation. The electrocatalyst of NiFe LDH/NiFeS exhibits outstanding performance towards HMF oxidation, about 98.5% yield for FDCA and 97.2% Faraday efficiency (FE) in the alkaline electrolyte with 10 mmol/L HMF, as well as excellent stability retaining 90.1% FE for FDCA after six cycles test. Moreover, even at an HMF concentration of 100 mmol/L, the yield and FE for FDCA remain high at 83.6% and 93.6%, respectively. These findings highlight that 2D heterostructure containing abundant interfaces between NiFe LDH nanosheets and NiFeS can enhance the intrinsic activity of LDH and thus promote the oxidation reaction kinetics. Additionally, the synergistic effect of the bimetallic NiFe compounds also improved the selectivity of HMF conversion to FDCA. Our present work demonstrates that constructing 2D ultrathin heterostructure of NiFe LDH/NiFeS is a facile strategy via interface engineering to enhance the intrinsic activity of LDH electrocatalysts, which would open new avenues toward low-cost and advanced 2D nanocatalysts for sustainable energy conversion and electrochemical valorization of biomass derivatives.

Partial Sulfidation of the Electrochemically Exfoliated Layered Double Hydroxides toward Advanced Aqueous Zinc Batteries

AbstractAqueous zinc‐based batteries are a promising alternative to lithium batteries. These batteries, however, persistently suffer from uncontrollable dendrite growth and sustained water consumption at the Zn anodes, along with low and often fading capacity at the cathodes. Herein, Zn metal is simply encapsulated into a chitosan‐containing polymer gel that not only suppresses hydrogen evolution but also enables dendrite‐free Zn plating/stripping. A binder‐free cathode based on the electrochemically exfoliated and partially sulfidated Ni–Co–Fe layered double hydroxide‐reduced graphene oxide (SNS‐rGO) nanocomposite is also reported. The fabricated devices (based on either Zn or chitosan‐coated Zn) deliver near record‐high values of specific capacity (756 mA h g−1cathode at 1 A g−1) and specific energy (1284 W h kg−1cathode), along with an outstanding specific power (108 kW kg−1cathode), an excellent output voltage (up to 1.9 V), and prolonged cycling stability at 100% depth‐of‐discharge. This interface engineering strategy, supported by the density functional theory calculations, provides a solid basis for further practical applications of aqueous Zn batteries.

Boosting electrocatalytic activity with the formation of abundant heterointerfaces and N, S dual-doped carbon nanotube for rechargeable Zn-air battery

Herein, a facile synthetic strategy is proposed to fabricate high-performance electrocatalysts for rechargeable Zn-air batteries (ZABs). Heterostructured NiCo/NiCo2S4 nanoparticles encapsulated in N-, S- co-doped CNT (NiCo/NiCo2S4@NSCNT) are synthesized via co-precipitation, thermal carbonization, and partial sulfidation processes. The strongly coupled NiCo/NiCo2S4 heterostructure can improve the redox property and charge transfer ability. Also, the CNTs with abundant foreign dopants provide high electrical conductivity and abundant defect sites for both the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). The prepared NiCo/NiCo2S4@NSCNT electrocatalyst exhibits a low overpotential of 349 mV at a current density of 10 mA cm−2 and a half-wave potential of 0.865 V for the OER and ORR, respectively. Moreover, the ZAB assembled using as-prepared NiCo/NiCo2S4@NSCNT can provide superior specific capacity (756.16 mA h gZn−1), peak power density (155.82 mW cm−2), and long-term cyclability compared to those of the precious metal-based electrocatalyst (Pt/C + RuO2).

Effect of synthesis conditions on the photocatalytic behavior of ZnS-ZnO heterojunctions for the H2 generation

In the present work, the synthesis and photocatalytic performance for H2 production of ZnS-ZnO composites at different compositions of cubic sphalerite (ZnS-c), hexagonal wurtzite (ZnS-h) and zincite (ZnO) phases are shown. The synthesis was carried out by the solvothermal method using mono ethylene glycol and thiourea as solvent and sulfur source, respectively, for the partial sulfidation of ZnO at different temperatures (150 °C, 200 °C, and 250 °C). When the temperature is increased in the solvothermal process, the hexagonal phase grows at the expense of the cubic phase. The materials as powders were characterized by X-ray diffraction, scanning and transmission electron microscopy, UV–visible spectroscopy, X-ray photoelectron microscopy, N2 adsorption-desorption isotherms, and photoelectrochemical techniques. These materials were applied in H2 production as an alternative source of clean and sustainable energy generation. It was found that the most photoactive material was the one synthesized at 200 °C, this photocatalyst presented an H2 production rate of 580 µmol h−1 g−1. The enhancement of the photocatalytic activity is due to the optimization of the interfacial properties between ZnS-c/ZnS-h and ZnO as a model system for coupled photocatalysts.

Ultra-uniform MIL-88B(Fe)/Fe3S4 hybrids engineered by partial sulfidation to boost catalysis in electro-Fenton treatment of micropollutants: Experimental and mechanistic insights

Fe-based metal–organic frameworks are promising catalysts for water treatment, although their viability is hampered by the slow regeneration of active Fe(II) sites. A facile sulfidation strategy is proposed to boost the catalytic activity of MIL-88B(Fe) in heterogeneous electro-Fenton (HEF) treatment of organic micropollutants at mild pH. The synthesized MIL-88B(Fe)/Fe3S4 hybrids possessed numerous and durable unsaturated iron sites, acting the S2− atoms as electron donors that enhanced the Fe(II) recycling. The sulfidated catalyst outperformed the MIL-88B(Fe), as evidenced by the 7-fold faster degradation of antibiotic trimethoprim by HEF and the fast destruction of micropollutants in urban wastewater. The hybrid catalyst was reused, obtaining >90% drug removal after four runs and, additionally, its inherent magnetism facilitated the post-treatment recovery. Electrochemical tests and DFT calculations provided mechanistic insights to explain the enhanced catalysis, suggesting that the accelerated Fe(III)/Fe(II) cycling and the enhanced mass transport and electron transfer accounted for the efficient trimethoprim degradation.

In-situ sulfidation to fabricate NiSx modified g-C3N4/NiO composite for efficient photocatalytic hydrogen production under visible-light

Graphitic carbon nitride is a very potential photocatalytic catalyst for H2 production, but its practical application is seriously limited by the fast recombination of photogenerated carriers and insufficient utilization of surface charge. In order to solve these problems, herein, a series of g-C3N4-NiO-NiSx photocatalysts were synthesized by first calcining the precursor to load NiO on g-C3N4 and subsequently partial sulfidation of NiO into NiSx in situ via a hydrothermal process. Under the irradiation of visible light, the photocatalytic H2 production rate of g-C3N4-NiO-0.4T can be up to 1248.1 μmol·g−1·h−1 using triethanolamine as sacrificial agent. In addition, recycling test also confirmed g-C3N4-NiO-0.4T has excellent photostability. It is believed that the formation of p-n junction between NiO and g-C3N4 and the presence of NiSx promote the spatially fast separation of photogenerated carriers, while the abundant interface of NiS2 and NiS also leads to the good proton trapping ability. These two factors jointly determine the efficient H2 production of the composite photocatalysts. Furthermore, the detailed energy band structure and plausible photocatalytic mechanism of g-C3N4-NiO-NiSx are also proposed. This work can offer a new route and useful reference for the design and research of high efficiency composite photocatalysts for H2 production.

Partial Sulfidation Strategy to NiFe‐LDH@FeNi2S4 Heterostructure Enable High‐Performance Water/Seawater Oxidation

AbstractThe development of a high‐performance electrocatalyst for oxygen evolution reaction (OER) is imperative but challenging. Here, a partial sulfidation route to construct Ni2Fe‐LDH/FeNi2S4 heterostructure on nickel foam (Ni2Fe‐LDH/FeNi2S4/NF) by adjusting the hydrothermal duration is reported. The heterostructures afford abundant hydroxide/sulfide interfaces that offer plentiful active sites, rapid charge and mass transfer, favorable adsorption energy to oxygenated species (OH− and OOH) evidenced by the density functional theory calculations, which synergistically boost the alkaline water oxidation. In the 1.0 m KOH solution, Ni2Fe‐LDH/FeNi2S4/NF exhibits an excellent OER catalytic activity with a much smaller overpotential (240 mV) to reach the current density of 100 mA cm−2 than single‐phase Ni2Fe‐LDH/NF (279 mV) or FeNi2S4/NF (271 mV). More impressively, 2000 cycles of cyclic voltammetry scan for water oxidation results in the formation of a sulfate layer over the catalyst. The corresponding post‐catalyst demonstrates better OER activity and durability than the initial one in the alkaline simulated seawater electrolyte. The post‐Ni2Fe‐LDH/FeNi2S4/NF delivers smaller overpotential (250 mV) at 100 mA cm−2 and longer stability time than the original form (260 mV). The post‐formed sulfate passivating layer is responsible for the outstanding corrosion resistance of the salty‐water oxidation anode since it can effectively repel chloride.

Activating and optimizing the MoS2@MoO3 S-scheme heterojunction catalyst through interface engineering to form a sulfur-rich surface for photocatalyst hydrogen evolution

As a crucial part of artificial photosynthesis, the design of the catalyst is important essential. Among them, the interface engineering between semiconductors and the construction of surface-active sites play a vital role in generating and transporting light-excited electrons, which can ultimately accelerate water decomposition. Therefore, the MoS2@MoO3 step (S)-scheme heterojunction photocatalyst was prepared by in-situ partial sulfidation. The excellent interface engineering of MoS2@MoO3 nanomaterials achieves a high surface reaction rate. The in-situ vulcanization strategy gradually corrodes from the outside to the inside. The introduction of sulfur atoms can replace oxygen atoms to build a sulfur-rich surface and generate molybdenum sulfide. The amount of thioacetamide is adjusted to control vulcanization and optimizing the experimental conditions, the best hydrogen production rate is 12416.8 µmol h−1 g−1. An in-situ irradiation XPS experiments and DFT calculations provide a deeper understanding of the S-scheme electron transport mechanism in MoS2@MoO3. MoS2@MoO3 interface interaction has penetrating electron channels and a strong interface interaction force, which effectively promotes the charge transfer between interfaces. This gradual surface vulcanization strategy provides new ideas for introducing synergistic surface-active sites and optimizing interface engineering photocatalyst projects.

Size-dependent electron injection over sensitized semiconductor heterojunctions for enhanced photocatalytic hydrogen production

Mechanistic understanding of the effect of electron transfer rate across the semiconductor heterojunction interface on its photocatalytic activity remains elusive. Herein, a series of sensitized semiconductor heterojunctions consisting of monodisperse CdS quantum dots (QDs) with controllable sizes range of 2.2–6.5 nm and cadmium tetrakis(4-carboxyphenyl)porphyrin (Cd-TCPP) nanosheets are constructed through partial sulfidation strategy. The in situ resultant CdS/Cd-TCPP composites exhibit size-dependent photocatalytic hydrogen evolution reaction (HER) activity with the highest activity of 3150 μmol·h−1·g−1 obtained at a medium CdS QD size of 4.8 nm. It is demonstrated that the interfacial electron transfer rate and the corresponding photocatalytic HER activity can be regulated by tuning the CdS QD size that determines the conduction band position of CdS relative to Cd-TCPP. This work provides a new strategy that rationally controls the interfacial electron transfer rate for developing highly efficient photocatalysts.

In Situ Partial Sulfidation for Preparing Cu/Cu2−xS Core/Shell Nanorods with Enhanced Photocatalytic Degradation

Herein, we report an approach to prepare Cu/Cu2−xS core/shell nanorods by in situ sulfidation of copper nanorods. Firstly, copper nanorods with tunable longitudinal surface plasmon resonances were synthesized by a seed-mediated method using Au nanoparticles as seeds. A convenient in situ sulfidation method was then applied to convert the outermost layer of Cu nanorods into Cu2−xS, to increase their stability and surface activity in photocatalytic applications. The thickness of Cu2−xS layer can be adjusted by controlling the amount of S source. The Cu/Cu2−xS core/shell nanorods exhibits two characteristic surface plasmon resonances located in visible and near-infrared regions, respectively. The photocatalytic performances of Cu nanorods and their derivatives were evaluated by measuring the degradation rate of methyl orange dyes. Compared with Cu nanorods, the Cu/Cu2−xS core/shell nanorods demonstrate more than a 13.6-fold enhancement in the degradation rate at 40 min. This work suggests a new direction for constructing derivative nanostructures of copper nanorods and exploring their applications.

Electronic modulation of NiS-PBA/CNT with boosted water oxidation performance realized by a rapid microwave-assisted in-situ partial sulfidation

Hydrogen is considered as the promising renewable resources in future C-free systems, but more efficient and scalable synthesis is required to enable its widespread deployment. Here, in-situ generated hierarchical NiS-PBA/CNT hybrid has been fabricated which combined the high conductivity and electrocatalytic activity together. Through study the electronic structure, it was found that the electron transfer among metal atom enable higher activity. The optimized NiS-PBA/CNT delivers an ultralow overpotential of 253 mV @ 20 mA cm−2, a small Tafel slope of 49.8 mV dec-1, and can work steadily for more than 40 h with a Faradic efficiency of 95.5%. Density functional theory calculations based on the NiS-PBA, NiS and PBA model reveal that the enhanced catalytic activities of NiS-PBA is mainly manifested in its lower free energy of rate-determining step (the oxidation of *OH to *O) and higher electrical conductivity. This work provides a novel partial sulfidation strategy for PBA to significantly boost catalytic performance. And the microwave-assisted solvothermal reaction offers a novel mild implementation toward in situ heterogeneous doping for carbon matrix.

Co-catalyst boosted photocatalytic hydrogen production driven by visible-light over g-C3N4: The synergistic effect between Ag and Ag2S

Developing a co-catalyst structure with a rational design is necessary to improve the photocatalytic performance. In this work, a series of g-C3N4/Ag-Ag2S photocatalysts were prepared by depositing Ag nanoparticles onto g-C3N4 through photoreduction, followed by a partial sulfidation of Ag into Ag2S via a solution method. Various characterizations were employed to investigate the crystal phase, composition, and morphology of the synthesized samples in detail. The evaluation results for photocatalytic H2 production show that g-C3N4/Ag-Ag2S-8 possesses a H2 production rate of 223.5 μmol g−1 h−1 when subjected to a 300 W xenon lamp for 5 h, which far exceeds those of the remaining as-prepared samples. Besides, g-C3N4/Ag-Ag2S-8 also exhibits an acceptable photostability in recycling experiments. Based on multiple measurements on the textural properties, optical properties, charge separation performances, and proton reduction abilities of the as-prepared samples, it is believed that the rapid separation of photogenerated carriers and excellent proton capturing ability caused by the rationally designed Ag-Ag2S co-catalyst are the two key factors that can result in the efficient photocatalytic H2 production observed in g-C3N4/Ag-Ag2S. Furthermore, a plausible mechanism for the photocatalytic H2 production in g-C3N4/Ag-Ag2S is also provided. Thus, this work may provide new insights into the future development of semiconductor composites for photocatalysis.

Partial sulfidation for constructing Cu2O–CuS heterostructures realizing enhanced electrochemical glucose sensing

A Cu2O–CuS heterostructure was constructed to elucidate the relationship between heterojunctions and electrochemical glucose sensing.

Subcellular Imaging of Localization and Transformation of Silver Nanoparticles in the Oyster Larvae.

To accurately assess the behavior and toxicity of silver nanoparticles (AgNPs), it is essential to understand their subcellular distribution and biotransformation. We combined both nanoscale secondary ion mass spectrometry (NanoSIMS) and electron microscopy to investigate the subcellular localization of Ag and in situ chemical distribution in the oyster larvae Crassostrea angulata after exposure to isotopically enriched 109AgNPs. Oyster larvae directly ingested particulate Ag, and in vivo dissolution of AgNPs occurred. The results collectively showed that AgNPs were much less bioavailable than Ag+, and the intracellular Ag was mainly originated from the soluble Ag, especially those dissolved from the ingested AgNPs. AgNPs absorbed on the cell membranes continued to release Ag ions, forming inorganic Ag-S complexes extracellularly, while Ag-organosulfur complexes were predominantly formed intracellularly. The internalized Ag could bind to the sulfur-rich molecules (S-donors) in the cytosol and/or be sequestered in the lysosomes of velum, esophagus, and stomach cells, as well as in the digestive vacuoles of digestive cells, which could act as a detoxification pathway for the oyster larvae. Ag was also occasionally incorporated into the phosphate granules, rough endoplasmic reticulum, and mitochondria. Our work provided definite evidence for the partial sulfidation of AgNPs after interaction with oyster larvae and shed new light on the bioavailability and fate of nanoparticles in marine environment.

Prolonging the antibacterial activity of nanosilver-coated membranes through partial sulfidation

Silver sulfidation in nanosilver-coated membranes slows down silver release and increase biofouling resistance without affecting the membrane's functionality.

Experimental and Theoretical Insights of MoS2/Mo3N2 Nanoribbon‐Electrocatalysts for Efficient Hydrogen Evolution Reaction

AbstractMoS2 is a promising material for electrocatalysis and opens up avenues for the development of non‐precious metal electrocatalysts for hydrogen evolution reaction in acidic media. However, the activity of MoS2 has been severely impeded because of its inferior conductivity. Herein, a nanoribbon‐like MoS2/Mo3N2 hybrid is successfully fabricated via partial sulfidation of Mo3N2 in H2S atmosphere. The synergistic effect between the high intrinsic activity of MoS2 and the desirable conductivity of Mo3N2 contributes to the overpotential at the current density of 10 mA cm−2 (η10) of 196 mV towards hydrogen evolution, distinctively lower than Mo3N2 (467 mV) and MoS2 (293 mV). The theoretical simulation discloses that the Gibbs free‐energy for the adsorption of atomic hydrogen (|ΔGH*|) for MoS2/Mo3N2 is less than that of others, and thus facilitating the hydrogen evolution.

A partial sulfidation approach that significantly enhance the activity of FeCo layered double hydroxide for oxygen evolution reaction

We report a partial sulfidation approach that effectively boosts the OER activity of FeCo-layered double hydroxides (LDH). It is found that the mild sulfurized FeCo-LDH nanosheets using Na2S converted a portion of their surface metal-hydroxide bonds to metal-sulfur (-hydrosulfide) bonds without significantly altering their crystal structure. The sulfidation degree is controlled by Na2S concentration for obtaining a moderately surface electronic configurations. Benefits from the regulated electronic configurations, the sulfurized FeCo-LDH nanosheets only require an overpotential of 281 mV to produce oxygen at 10 mA cm−2 and their Tafel slope is 51.8 mV dec−1, which are both lower than the 348 mV and 72.7 mV dec−1 of pristine FeCo-LDH nanosheets. The sulfurized catalysts have sustained 12 h of operation without notable activity loss. This work can provide new insights into understanding the roles of metal-sulfur bonds for OER and offer an attractive strategy to design low cost but efficient OER catalysts.

Novel ZnS-ZnO composite synthesized by the solvothermal method through the partial sulfidation of ZnO for H2 production without sacrificial agent

Novel ZnS-ZnO composites were synthesized by the solvothermal method from the partial sulfidation of ZnO using thiourea at low temperatures. The synthesized materials were active for the photocatalytic production of H2 with and without the presence of sacrificial agent without the addition of a co-catalyst; in the present paper, methanol was evaluated as sacrificial agent, increasing the amount of H2 produced up to five times compared to the most active photocatalyst without using sacrificial agent. All the materials were characterized by XRD, N2 Physisorption, FT-IR, XPS, Diffuse Reflectance Spectroscopy, and HR-TEM. In addition, the materials were characterized by photo-electrochemical techniques to explain the photocatalytic behavior. The most active material was the composite with an atomic ratio of S/Zn = 0.71 synthesized at 100 °C, producing 247 μmol H2 h−1 g−1, the H2 production rate was improved five times with the addition of methanol as sacrificial agent. The improvement of the photocatalytic activity was attributed to the formation of the heterojunction at the interface formed between ZnO and ZnS, promoting a higher electron transfer to the conduction band and a lower charge transfer resistance from the catalyst surface to the solution reaction.