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Self-supported NiCo 2 O 4 @Ni 1.18 S core-shell nanocomposite were synthesized on nickel foams by uniform growth Ni 1.18 S nanosheets encircling NiCo 2 O 4 nanoneedles. Characterization results demonstrate that NiCo 2 O 4 @Ni 1.18 S core-shell nanocomposite have significant advantages in one - and two-dimensional nanostructure coordination structure, with richer REDOX active sites and more energy storage paths. Density functional theory (DFT) calculations results indicate that the surficial adsorption energy with OH− ions is enhanced in NiCo 2 O 4 @ Ni 1.18 S nanocomposite, thereby facilitating the reversible redox reaction kinetics and the electrochemical activity. As a result, self-supported NiCo 2 O 4 @Ni 1.18 S core-shell nanocomposite exhibit excellent energy-storage properties, i.e.: the specific charge capacity of 3158 F g−1 at 1 A g−1, high rate performance of 52.3 % from 1 A g−1 to 5 A g−1, and the 81.25 % capacity retention rate after 5000 cycles. Especially, it should be pointed out that the hybrid supercapacitors assembled from self-supported NiCo 2 O 4 @Ni 1.18 S core-shell nanocomposite and activated carbon present the wide voltage window (0–1.6 V), high energy density of 100.3 Wh kg−1 at power density of 177 W kg−1 and prospective commercial consideration. These facts fully prove the practical feasibility of self-supported NiCo 2 O 4 @Ni 1.18 S core-shell nanocomposite in advanced energy-storage facilities. [Display omitted] • NiCo 2 O 4 @Ni 1.18 S core-shell nanocomposite are constructed by hydrothermal-calcination-electrodeposition method. • This core-shell nanostructure has the structural advantages and composition complementariness. • Hybrid supercapacitors are assemled based on core-shell NiCo 2 O 4 @Ni 1.18 S and active carbon. • Hybrid device is promising for smart watches, electric vehicles, and wearable electronics, etc. [ABSTRACT FROM AUTHOR]

Photo-assisted energy storage systems, by which solar energy can be both converted and stored, have been of interest in the past few years. Novel energy conversion and storage technology is offered by photo-supercapacitors through the combination of an energy collecting unit and a supercapacitor. This dual-application system effectively generates and stores power in a single device, which makes it appropriate for various purposes. In this work, the electrochemical anodization-electrodeposition has been employed to fabricate manganese-nickel sulfide (Mn–Ni–S) nanostructures on titania nanotubes (TNs) and used them as photoelectrodes in photo-supercapacitors. The high surface area and improved properties make TNs considerably important for energy production and storage. Photoelectrochemical analysis was carried out in a three-electrode system under a xenon (Xe) lamp irradiation using the film prepared as the photoelectrode. The highest photocurrent and photovoltage were shown by MnNiS-3/TN electrode, indicating its superior photosensitivity. Upon illumination under a 0.7 mA/cm2 current density, the area-specific capacitance of MnNiS-3/TN electrode increased from 388.3 to 723.3 mF/cm2, which is 2.0, 3.6, and 12.8 times higher than the corresponding values for NiS/TN, MnS/TN, and bare TN electrodes under similar conditions, respectively. This indicates the considerable enhancement of the capacitance of this electrode induced by light. The desirable light-sensitive properties of MnNiS/TN make it capable of simultaneous solar energy harvesting and storage. Light sensitivity makes it possible to charge MnNiS/TN optically. More importantly, upon light irradiation, the capacity can be increased from 374.7 to 630.2 mF/cm2 (current density 0.5 mA/cm2) compared to the corresponding value in the dark. Using MnNiS-3/TN as the best photoelectrode and MnS/FTO, NiS/FTO, MnNiS-1/FTO, MnNiS-2/FTO, and MnNiS-3/FTO as the counter electrodes, photo-charged through light illumination on their surfaces, five asymmetric solid-state photo-supercapacitors (ASSPS) were prepared. MnNiS-3/TN//MnNiS-3/FTO device showed the largest CV curve area, which indicated its highest areal capacitance. High capacitance gain under irradiation (155.7% at 2.0 mA/cm2) and outstanding capacitance maintenance (97.9% over 10000 cycles) were shown by this ASSPS. Furthermore, a great energy density of 4855.4 mWh/cm2 was shown by the MnNiS-3/TN//MnNiS-3/FTO device under light irradiation. This research introduces a novel approach to the development of powerful solar energy conversion/storage devices. [Display omitted] • Mn–Ni sulfides with various Mn/Ni ratios have been grown on titania by co-electrodeposition. • The highest photocurrent and photovoltage were shown by MnNiS-3/TN. • Upon illumination, the area-specific capacitance of MnNiS-3/TN electrode increased from 388.3 to 723.3 mF/cm2. • Using MnNiS-3/TN as the best photoelectrode, five asymmetric solid-state photo-supercapacitors (ASSPS) were prepared. • High capacitance gain under irradiation (155.7% at 2.0 mA/cm2) and outstanding capacitance maintenance (97.9% over 10000 cycles) were shown by this ASSPS. [ABSTRACT FROM AUTHOR]

Efficient and cost-effective catalysts for hydrogen evolution reaction (HER) are essential for large-scale hydrogen production, which is a critical step toward reducing carbon emissions and advancing the global transition to sustainable energy. Nickel sulfide-based catalysts, which exist in various stoichiometries, show promise for HER in alkaline media. However, as single-phase materials, they do not demonstrate superior activity compared to Pt-based catalysts. This review highlights recent strategies to enhance the HER performance of nickel sulfides, including heteroatom doping, heterostructure construction, and vacancy engineering, tailored to their different stoichiometric ratios. The study also examines synthesis methods, characterizations, and their impact on HER performance. Furthermore, it discusses the challenges and limitations of current research and suggests future directions for improvement. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal CrystEngComm, which focuses on the design and understanding of solid-state and crystalline materials. The contents list includes various articles on topics such as halogen bonding in crown ether chemistry, metal-organic framework-derived materials for enhanced performance of aqueous zinc ion batteries, and the effect of grain boundary doping on the mechanical behavior of Ta bicrystal. The journal is published by The Royal Society of Chemistry, a leading chemistry community. [Extracted from the article]

Nickel sulfides prepared using conventional methods usually exhibit bulk structure and multiple phases, which pose great challenges for controllably synthesizing designer particles with high performance. Herein, we developed a novel and universal strategy to regulate the crystal phase and structure of nickel sulfide through an acid- or alkaline-induced strategy. We found that HCl and KOH could partially extract nickel and sulfur from nickel sulfide under a hydrothermal process, respectively. As a result, HCl treatment induced the transformation of nickel sulfide from nickel-rich phase (NiS) to nickel-deficient phase (NiS2) and bulk structure to micro–nano structure. The KOH treatment induced the transformation of nickel sulfide from a sulfur-rich phase (NiS2) to a sulfur-deficient phase (NiS), as well as the changes in surface microstructure. Attributed to the structural advantages brought by structure reconstruction, these samples exhibit enhanced electrochemical properties after the treatment. This is a unique and significant finding to the structure-regulation method of transition metal sulfides and will enrich their structure-dependent applications in supercapacitors or batteries. [ABSTRACT FROM AUTHOR]

Fe and Mo co-doped Ni 3 S 2 nanorod array is in situ built on Ni foam using Keplerate polyoxomolybdate as precursor and performs efficiently for electrocatalytic overall water splitting, capable of achieving a low cell voltage of 1.60 V and Faradaic efficiency of nearly 100%. [Display omitted] • Free-standing Fe and Mo co-doped Ni 3 S 2 nanorod array is in situ built on Ni foam using Keplerate polyoxomolybdate as precursor. • Fe-MoS 2 /Ni 3 S 2 @NF is reported first time for overall water splitting. • Fe and Mo co-doping modulates the electronic structure of Ni 3 S 2 and induces abundant active sites. • Fe-MoS 2 /Ni 3 S 2 @NF attains a more exceptional electrochemistry improvement, faster electron transfer, better reaction kinetics and long-term durability. Heazlewoodite nickel sulfide (Ni 3 S 2) is advocated as a promising nonnoble catalyst for electrochemical water splitting because of its unique structure configuration and high conductivity. However, the low active sites and strong sulfur–hydrogen bonds (S–H ads) formed on Ni 3 S 2 surface greatly inhibit the desorption of H ads and reduce the hydrogen and oxygen evolution reaction (HER and OER) activity. Doping is a valid strategy to stimulate the intrinsic catalytic activity of pristine Ni 3 S 2 via modifying the active site. Herein, the Ni foam supported Fe and Mo co-doped Ni 3 S 2 electrocatalysts (Fe-MoS 2 /Ni 3 S 2 @NF) have been constructed using Keplerate polyoxomolybdate {Mo 72 F 30 } as precursor through a facile hydrothermal process. Experimental results certificate that Fe and Mo co-doping can effectively tune the local electronic structure, facilitate the interfacial electron transfer, and improve the intrinsic activity. Consequently, the Fe-MoS 2 /Ni 3 S 2 @NF display more excellent HER and OER activity than MoS 2 /Ni 3 S 2 @NF and bare Ni 3 S 2 @NF by delivering the 10 and 50 mA cm−2 current densities at ultra-low overpotentials of 74/175 and 80/160 mV for HER and OER. Moreover, when coupled in an alkaline electrolyzer, Fe-MoS 2 /Ni 3 S 2 @NF approached the current of 10 mA cm−2 under a cell voltage of 1.60 V and exhibit excellent stability. The strategy to realize tunable catalytic behaviors via foreign metal doping provides a new avenue to optimize the water splitting catalysts. [ABSTRACT FROM AUTHOR]

Anion exchange membrane (AEM) water electrolysers have shown their potential in green hydrogen production. One of the crucial tasks is to discover novel cost‐effective and sustainable electrocatalyst materials. In this study, a low‐cost Ni−S‐based catalyst for hydrogen evolution reaction was prepared via a simple electrodeposition process from a modified Watts bath recipe. Physical characterisation methods suggest this deposit film to be amorphous. Optimisation of the electrodeposition parameters of the NixSy catalyst was carried out using a rotating disk electrode setup. The optimised catalyst exhibited excellent catalytical performance in 1 M KOH on a microelectrode, with overpotentials of 41 mV, 111 mV and 202 mV at 10, 100 and 1000 mA cm−2 with Tafel slope of 67.9 mV dec−1 recorded at 333 K. Long‐term testing of the catalyst demonstrated steady performance over a 24 h period on microelectrode at 100 mA cm−2 with only 71 mV and 37 mV overpotential increase at 293 K and 333 K respectively. Full cell testing with the optimised NixSy as cathode and NiFe(OH)2 as anode showed 1.88 V after 1 h electrolysis at 500 mA cm−2 in 1 M KOH under 333 K with FAA‐3‐30 membrane. [ABSTRACT FROM AUTHOR]

A series of physical mixtures of Na4P2S6 and NiCl2 (P‐NiPS(x), where x represents the P/Ni molar ratio) were employed for the preparation of Ni2P. For comparison, a sulfur‐containing Ni2P catalyst (Ni2P‐S) and a sulfur‐free Ni2P catalyst (Ni2P‐TPR) were prepared by reduction of Ni2P2S6 and a nickel phosphate precursor, respectively. The reduction of the P‐NiPS(x) precursors with P/Ni ratios above 2/3 yielded Ni2P catalysts with a distinct nickel phosphosulfide layer (NiPS(x)), and the Ni2P phase started to form at ca. 200 °C. The reduction of Ni2P2S6 to Ni2P most likely follows a disproportionation mechanism. The P3+ species in Ni2P2S6 disproportionate to PH3 and P5+ during the reduction, and PH3 further reacts with nickel and sulfur species to form Ni2P and the surface nickel phosphosulfide layer. The sulfur atoms in the nickel phosphosulfide phase were in the form of S2−. The introduction of sulfur to Ni2P favored the hydrogenation pathway of the hydrodesulfurization (HDS) of dibenzothiophene (DBT), but hardly affected the direct desulfurization (DDS) pathway and inhibited the hydrogenation of biphenyl. The DDS pathway rate constants of DBT HDS over the Ni2P‐TPR and NiPS(x) catalysts were observed to increase linearly with the increase in their surface Ni atomic concentrations. [ABSTRACT FROM AUTHOR]

Developing low‐cost and exceedingly efficient electrocatalysts for oxygen evolution reaction (OER) is vital for application of hydrogen production from water splitting. Herein, three different nickel sulfides on nickel foam were fabricated via a simple sulfuring the as‐formed Ni‐MOF with different sulfide as the sulfur source. The effect of sulfur source on OER performance, morphology and structure of the as‐prepared product are well discussed. The optimized Ni‐MOF/NF‐SS deliver overpotentials of 253 and 330 mV to reach current densities of 10 and 100 mA cm−2 with a small Tafel slope of 70.9 mVdec−1, and stability of over 50 h. This work provides insights into the relationship between the OER activity and the structures of nickel sulfides, but also affords a new route to fabricate nickel sulfides‐based electrocatalysts for OER. [ABSTRACT FROM AUTHOR]

A series of physical mixtures of Na4P2S6 and NiCl2 (P‐NiPS(x), where x represents the P/Ni molar ratio) were employed for the preparation of Ni2P. For comparison, a sulfur‐containing Ni2P catalyst (Ni2P‐S) and a sulfur‐free Ni2P catalyst (Ni2P‐TPR) were prepared by reduction of Ni2P2S6 and a nickel phosphate precursor, respectively. The reduction of the P‐NiPS(x) precursors with P/Ni ratios above 2/3 yielded Ni2P catalysts with a distinct nickel phosphosulfide layer (NiPS(x)), and the Ni2P phase started to form at ca. 200 °C. The reduction of Ni2P2S6 to Ni2P most likely follows a disproportionation mechanism. The P3+ species in Ni2P2S6 disproportionate to PH3 and P5+ during the reduction, and PH3 further reacts with nickel and sulfur species to form Ni2P and the surface nickel phosphosulfide layer. The sulfur atoms in the nickel phosphosulfide phase were in the form of S2−. The introduction of sulfur to Ni2P favored the hydrogenation pathway of the hydrodesulfurization (HDS) of dibenzothiophene (DBT), but hardly affected the direct desulfurization (DDS) pathway and inhibited the hydrogenation of biphenyl. The DDS pathway rate constants of DBT HDS over the Ni2P‐TPR and NiPS(x) catalysts were observed to increase linearly with the increase in their surface Ni atomic concentrations. [ABSTRACT FROM AUTHOR]

The main goal of this paper is to determine the order of the paragenetic sequence and phase transitions of the Ni–Fe sulfide association hosted in listvenites. Listvenites are hydrothermally altered mafic and ultramafic rocks that are often associated with active tectonic settings, such as transform faults, suture zones, and regional extensional faults, usually in contact with volcanic or carbonate rocks. Listvenitization is displayed by a carbonation process when the original olivine, pyroxene, and serpentine group minerals are altered to Mg–Fe–Ca carbonates (magnesite, calcite, dolomite, and siderite), talc, quartz, and accessory Cr spinel, fuchsite, and Ni–Fe sulfides. The formed rocks are highly reactive; therefore, very often, younger hydrothermal processes are observed, overprinting the mineralogy and geochemistry of the original listvenitization products, including accessory Ni–Fe sulfide paragenesis. The studied samples of listvenites were collected from two locations in Kosovo (Vardar Zone): Janjevo and Melenica. The Ni–Fe sulfide textures and relationships with the surrounding listvenite-hosted minerals were obtained using reflected and transmitted light microscopy, while their chemical composition was determined using an electron microprobe. They form accessory mono-or polymetallic aggregates that usually do not exceed 100 μm in size disseminated in the studied listvenites. Generally, the paragenetic sequence of Ni–Fe sulfides is divided into three stages. The first pre-listvenite magmatic phase is represented by pentlandite and millerite. The second listvenite stage consists of Ni–Co bearing pyrite I (Ni content up to 11.57 wt.% [0.24 apfu], and Co content up to 6.54 wt.% [0.14 apfu]) and differentiated thiospinels (violarite + siegenite ± polydymite). The last, late listvenite stage is represented by younger gersdorffite−ullmannite and base metal mineralization: pyrite + marcasite + sphalerite + galena ± chalcopyrite ± sulfosalts. The findings obtained should help in the interpretation of many disseminated accessory Ni–Fe–Co mineralizations associated with mafic and ultramafic rocks worldwide. [ABSTRACT FROM AUTHOR]

Nickel is an important raw metal material in industry, which has been identified as a strategic mineral resource by the Chinese Ministry of Land and Resources. Nickel sulfide ore accounts for 40% of all nickel ores worldwide. However, magnesium silicate gangue minerals in sulfide nickel ores, particularly serpentine, pose significant challenges to the flotation of nickel sulfide ores. The presence of magnesium silicate gangue leads to a series of issues, including increased energy consumption in subsequent smelting processes, accelerated equipment wastage, and increased SO2 emissions, which severely impact the comprehensive utilization of nickel resources in sulfide nickel ores. In this regard, flotation depressants are the most direct and effective method to reduce adverse influences caused by magnesium silicate gangue in the flotation of nickel sulfide ore concentrate. Based on the characteristics of the typical magnesium-containing nickel sulfide ore, this review illustrates the difficulties of the depression of magnesium silicate gangue during the flotation of nickel sulfide ore and gives an overview of the common depressants from six aspects (chelation depressants, dispersion depressants, flocculation depressants, depressants for grinding, depressants for slurry adjustment and combination depressants). Each section summarizes the relevant depression mechanisms and analyzes the advantages and disadvantages of various reagents, providing a reference for designing depressants specifically targeting serpentine. [ABSTRACT FROM AUTHOR]

A series of Ni3S2 electrocatalysts were successfully prepared using nickel foam precursor as substrate and thiourea, sodium thiosulfate pentahydrate, sodium sulfide nonahydrate and sodium diethyldithiocarbamate as sulfur sources, and their performances in electrocatalytic hydrogen evolution (HER) were further compared. The results exhibited that the Ni3S2 catalyst prepared with sodium thiosulfate pentahydrate as the sulfur source showed the best performance in HER. At a current density of 10 mA cm−2, the overpotential was only 178 mV, and the Tafel slope was 70.4 mV dec−1. In addition, through the double-layer capacitance test, it was found that the catalyst had the highest electrochemical active area, and the capacitance reached 41.33 mF cm−2, which was consistent with its excellent HER performance. In this work, the influence mechanism of different sulfur sources on the sulfurization process of Ni3S2 catalyst and the further impact of these effects on the performance of HER were also discussed in detail. These results provide a solid theoretical and experimental basis for optimizing the application of Ni3S2 catalyst in the field of electrocatalytic hydrogen production. [ABSTRACT FROM AUTHOR]

The inclusion of ruthenium (Ru) to decorate nickel sulphide (Ru@NiS/Ni foam) resulted in a highly efficient electrocatalyst for the alkaline HER by enhancing water dissociation at the interface and reducing the energy barrier of the Volmer step. This strategic fusion significantly boosts the catalyst's performance in facilitating hydrogen production. [ABSTRACT FROM AUTHOR]

Recently, Ni‐based chalcogenides havedemonstrated remarkable activity and selectivity for alcohol electrooxidation, but the mechanisms remain debated. This study synthesizes Ni‐based electrodeswith different chalcogen anion coordination on nickel nanorod arrays (NiOx/Ni,NiSx/Ni, and NiSex/Ni NRAs). NiSex/Ni NRAsshowcases superior performance (Faradaic efficiency 92.9%) in glycerolelectrooxidation reaction (GOR). In situ spectroscopy reveals that NiSecoordination inhibits deep oxidative reconstruction of the Ni‐based interface, preventingNiOOH phase formation during GOR, enhancing activity and stability of NiSex/NiNRAs. Conversely, NiS and NiO coordination lead to deep reconstruction with NiOOHphase formation, limiting GOR performance. Differently, during competingreaction of GOR, the oxygen evolution reaction (OER) leads to deepreconstruction of NiSex interface due to the instability of Ni‐Sebonds, inducing performance degradation and dissolution of Se components. Furthermechanism investigation elucidates that the rate‐determining step (RDS) ofGOR at the NiSex interface involves oxidation of *C2H3O3 intermediatesthrough H2O adsorption, favoring stable formate production.Contrarily, the RDS at the NiSx, NiOx, and NiOOHinterfaces predominantly focus on the decarboxylation of multi‐carbon intermediates, raisingenergy barriers and over‐oxidizing formate to CO2. These results providenew insights for designing Ni‐based non‐oxide catalysts forefficient and stable electrocatalytic oxidation. [ABSTRACT FROM AUTHOR]

Hydrogen is an important energy carrier without carbon emissions. To achieve a carbon‐neutral world, the demand for hydrogen is very significant. In the process of producing green hydrogen, water splitting using electrocatalysts is a desirable process among many methods. The ideal electrocatalyst for hydrogen evolution is the platinum group of metals; however, the limitations of high cost and low abundance hinder large‐scale hydrogen production. Hence, researchers are trying to develop materials from more abundant and less expensive. Hence, in this review, we focus on the fundamental principles of hydrogen evolution reaction (HER) and various synthesis methods and strategies. From the material perspective, we focus on nickel sulfide‐based nanomaterials of different phases during the last four years of development. We compared the electrocatalyst parameters concerning the synthesis methods and strategies chosen. Finally, we have also discussed future challenges. Ultimately, by synthesizing the collective knowledge amassed in the field of HER research, this review endeavors to offer a comprehensive resource for researchers, engineers, and policymakers striving to advance hydrogen‐based energy technologies. In doing so, we aspire to foster continued innovation and collaboration toward realizing a sustainable energy future powered by hydrogen. [ABSTRACT FROM AUTHOR]

Hydrogen is an efficient and environmentally friendly energy source, and the development of cost-effective electrocatalysts is crucial for improving the efficiency of hydrogen production by water electrolysis. Despite the excellent electrolysis efficiency of noble metal catalysts, their cost and reserves have hindered commercial applications, so more attention has been paid to the study of non-precious metal catalysts in recent years. Nickel sulfide phase composites with various structures offer a wide scope for modification engineering of electrocatalysts and are ideal for electrocatalytic materials. In this work, we comprehensively review the research progress of nickel sulfide phase composites, focusing on the synthesis strategies of nickel sulfide composites as well as the four main modifications affecting the performance of electrolytic water: morphology engineering, heterogeneous structures, defect engineering, and substrate materials. It is found that the impact on electrolytic water properties is multiplied by utilizing clever modifications. Finally, the limitations of the current research on nickel sulfide phase electrocatalytic materials are analyzed. [Display omitted] • The special properties of nickel sulfide-based electrocatalytic materials are discussed. • The synthesis strategies of nickel sulfide-based materials were summarized and compared. • The modification strategies of nickel sulfide-based electrocatalysts are analyzed. [ABSTRACT FROM AUTHOR]

The ongoing pursuit of cost-effective approaches for synthesizing transition metal sulfide heterostructure oxygen evolution electrocatalysts, with the objective of optimizing active site exposure and stabilizing spatial framework, remains a significant challenge. In this study, self-supported bimetallic iron-nickel sulfide (Fe 1-x S-NiS/NF) nanosheet heterostructures were successfully fabricated in situ on nickel foam through the direct sulfurization of bimetallic carbonate precursors. The effects of sulfurization temperature and Fe content on the oxygen evolution reaction (OER) performance of the catalyst are investigated, and the best conditions are found to be 350 °C and 2 mmol, respectively. As expected, the optimized catalyst demonstrates remarkable OER performance in an alkaline solution with low overpotentials of 235 mV and 333 mV at high current densities of 50 mA cm−2 and 100 mA cm−2, respectively. Furthermore, the catalyst shows long-term stability lasting for 35 h at 60 mA cm−2 with a negligible shift in the polarization curve observed even after 2000 cyclic voltammetry cycles, while also exhibiting good structural preservation. The current study has the potential to offer valuable insights into the fabrication of electrocatalysts based on metal sulfide heterostructures. A simple hydrothermal-sulfurization strategy was adopted to fabricate series of self-supported iron-nickel sulfide nanosheet heterostructures catalysts with excellent OER performance. [Display omitted] • Self-supported Fe 1-x S-NiS/NF nanosheets were synthesized by sulfurization of carbonates. • Effects of sulfurization temperature and Fe content on the OER performance are investigated. • The Fe 1-x S-NiS/NF-2 catalyst exhibits excellent OER performance. [ABSTRACT FROM AUTHOR]

Developing highly efficient and stable electrocatalysts for urea electro-oxidation reactions (UORs) will improve wastewater treatment and energy conversion. A low-cost cobalt sulfide-anchored nickel sulfide electrode (CoS/Ni3S2@CP) was synthesized by electrodeposition in DMSO solutions and found to be highly effective and long-lasting. The morphology and composition of catalyst surfaces were examined using comprehensive physicochemical and electrochemical characterization. Specifically, CoS/Ni3S2@CP electrodes require a potential of 1.52 volts for a 50 mA/cm2 current, confirming CoS in the heterointerface CoS/Ni3S2@CP catalyst. Further, the optimized CoS/Ni3S2@CP catalyst shows a decrease of 100 mV in the onset potential (1.32 VRHE) for UORs compared to bare Ni3S2@CP catalysts (1.42 VRHE), demonstrating much greater performance of UORs. As compared to Ni3S2@CP, CoS/Ni3S2@CP exhibits twofold greater UOR efficiency as a result of a larger electroactive surface area. The results obtained indicate that the synthetic CoS/Ni3S2@CP catalyst may be a favorable electrode material for managing urea-rich wastewater and generating H2. [ABSTRACT FROM AUTHOR]

A novel nanocomposite film synthesized from an inexpensive and easily accessible polymer such as poly (vinyl alcohol) (PVA), which is coated with nickel sulfide (NiS) and graphene oxide (GO), was obtained from used drinking-water bottles. The produced coated film was examined as a potential photocatalyst film for wastewater treatment promotion in a batch system for the removal of methylene blue (MB) and tetracycline (TC) antibiotics. The experimental results show that the presence of GO significantly increases the photocatalytic efficiency of NiS, and the MB and TC degradation results proved that the incorporation of GO with NiS led to a more than one-and-a-half-fold increase in the removal percentage in comparison with the NiS/PVA-coated film. After 30 min of illumination using GO/NiS/PVA-coated film, the removal efficiency reached 86% for MB and 64% for TC. The photodegradation kinetic rate followed the pseudo-first-order rate. Furthermore, the response surface methodology (RSM) model was utilized to study and optimize several operating parameters. The ideal circumstances to achieve 91% elimination of MB are 12 mg L−1 MB initial concentration, two lamps, and an illumination time of 15 min; however, to achieve 85% TC removal, 11 mg L−1 TC initial concentration, two lamps, and a 45 min illumination time should be used. The fabricated nanocomposite photocatalyst film seems to have promise for use in water purification systems. [ABSTRACT FROM AUTHOR]

Hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs) are crucial for renewable energy production. Developing stable, cost-effective, and highly catalytic HER and OER electrocatalysts is paramount. In this study, a combination of hydrothermal synthesis and annealing was used to fabricate nickel sulfide (Ni3S2) particle–embedded nanotubes supported on nickel (Ni) foam (Ni3S2 PN/NF). The Ni3S2 PN/NF structures featured a highly branched morphology with a large specific surface area, surpassing that of conventional Ni metal nanotubes. This design increased the number of reactive sites and enhanced the charge-transfer process. The Ni foam substrate expanded the contact area of Ni3S2, thereby improving conductivity and facilitating the adsorption/desorption of intermediates on the Ni3S2 surface. Density functional theory calculations showed that the electronic structure of Ni3S2 provides excellent conductivity. Moreover, the multi-branched structure and inherent conductivity of the NiS nanomaterials enhanced the Ni3S2 PN/NF performance in 1M KOH, with overpotentials of 87 and 210 mV with iR compensation at 10 mA cm−2 for the HER and OER, respectively. The synthesized Ni3S2 PN/NF also exhibited robust durability for 20 h. These results demonstrate that Ni3S2 PN/NF is an excellent catalyst for both HER and OER. [ABSTRACT FROM AUTHOR]

MoS 2 /Ni 3 S 2 interfacial heterojunction is constructed and exhibits superior activity of promoting oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) towards efficient electrocatalytic water splitting process. [Display omitted] In the ongoing quest for cost-effective and durable electrocatalysts for hydrogen production—a critical element of sustainable energy transformation—the 1T phase of Molybdenum Disulfide (MoS 2) faces challenges due to its thermodynamic instability and the trade-off between efficiency and durability. Conversely, the 2H phase of MoS 2 , often disregarded in favor of the metallic 1T phase, suffers from its inert nature and limited active sites. To overcome these limitations, this study employs a straightforward hydrothermal synthesis strategy that couples both 1T and 2H phases of MoS 2 with Ni 3 S 2 , forming 1T- and 2H- MoS 2 /Ni 3 S 2 heterojunctions. Enhanced by Ni 3 S 2 ′s abundant active sites, improved electron transport capabilities, synergistic interface effects, and better structural stability, these heterojunctions achieve a high current density exceeding 500 mA cm−2 at low overpotentials, along with prolonged durability for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline electrolytes. Remarkably, an electrolyzer assembly utilizing 1T-MoS 2 /Ni 3 S 2 as the cathode and 2H-MoS 2 /Ni 3 S 2 as the anode demonstrates a competitive voltage of 1.58 V at 20 mA cm−2, showcasing superior performance in overall water splitting compared to other non-noble metal-based electrocatalysts. This study not only offers a viable method for synthesizing efficient and stable electrocatalysts for water splitting using transition metal-based heterogeneous structures but also addresses the fundamental challenges associated with 1T and 2H phases of MoS 2. [ABSTRACT FROM AUTHOR]

Enhanced electrocatalysts that are cost‐effective, durable, and derived from abundant resources are imperative for developing efficient and sustainable electrochemical water–splitting systems to produce hydrogen. Therefore, the design and development of non–noble–based catalysts with more environmentally sustainable alternatives in efficient alkaline electrolyzers are important. This work reports ferrocene (Fc)‐incorporated nickel sulfide nanostructured electrocatalysts (Fc−NiS) using a one–step facile solvothermal method for water–splitting reactions. Fc−NiS exhibited exceptional electrocatalytic activity under highly alkaline conditions, evident from its peak current density of 345 mA cm−2, surpassing the 153 mA cm−2 achieved by the pristine nickel sulfide (NiS) catalysts. Introducing ferrocene enhances electrical conductivity and facilitates charge transfer during water–splitting reactions, owing to the inclusion of iron metal. Fc−NiS exhibits a very small overpotential of 290 mV at 10 mA cm−2 and a Tafel slope of 50.46 mV dec−1, indicating its superior charge transfer characteristics for the three–electron transfer process involved in water splitting. This outstanding electrocatalytic performance is due to the synergistic effects embedded within the nanoscale architecture of Fc−NiS. Furthermore, the Fc−NiS catalyst also shows a stable response for the water–splitting reactions. It maintains a steady current density with an 87% retention rate for 25 hours of continuous operation, indicating its robustness and potential for prolonged electrolysis processes. [ABSTRACT FROM AUTHOR]

Constructing effective active sites on photocatalysts is key to promoting H 2 evolution activity. Although nickel sulfides are found to be non-noble cocatalysts with high cocatalytic performance, the effect of the S element on H 2 evolution still needs to be clarified. Herein, NiS x (x = 0, 1 and 2) cocatalysts are successfully anchored respectively on the surface of porous g-C 3 N 4 via the same solid-state method. The combined experimental and theoretical calculations reveal that an intimate Schottky junction constructed between metallic NiS x and PCN impels the rapid transfer of electrons from PCN to NiS x. , which promotes a charge separation efficiency and enhances photocatalytic activity. Furthermore, the introduction of the S in the NiS x lattice regulates the adsorption and desorption energies of reactant (H+) and product (H 2), determining the H 2 -evolving performance. Among the Ni, NiS and NiS 2 cocatalysts, the S element in the NiS adjusts the equilibrium of adsorption and desorption for H+/H 2 , resulting in the most favorable thermodynamics of H 2 evolution. The maximum H 2 -rate of NiS/PCN reaches 142.9 μmol h−1, which is 4.3 and 1.6 times of Ni/PCN and NiS 2 /PCN. Our results gain a deeper understanding of the mechanism that transition metal dichalcogenide based cocatalysts promote photocatalytic activity. [Display omitted] • NiS x (x = 0, 1, 2) is anchored on PCN using the same facial solid-state method. • S in the NiS x regulates the energies of adsorption and desorption for H+/H 2. • NiS with near-zero ΔG H* causes the rapid reduction of protons to H 2. • The AQY of hydrogen evolution on 2.5% NiS/PCN at λ = 420 nm reaches 23.4%. [ABSTRACT FROM AUTHOR]

Developing efficient, low-cost and bifunctional catalysts with predominant durability for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) is an extraordinary challenge in the preparation of green hydrogen energy by electrochemical water splitting. Three-dimensional (3D) transition metal compounds have become a research hotspot as OER electrocatalysts, which can replace noble metal oxides such as RuO 2 and IrO 2 to reduce application costs. Herein, we synthesized a novel three-dimensional pine-tree-like bimetallic sulfide arrays on nickel foam (FeCoS/NF) using various optimization strategies such as morphology optimization, in situ growth and introduction of heterogeneous structures. The as-synthesized FeCoS/NF electrocatalyst only requires relatively low overpotential of 156 mV to achieve a current density of 20 mA cm−2 for OER, with a Tafel slope of only 37 mV dec−1. It also has a small charge transfer resistance, an electrochemical surface area and good electrochemical stability in alkaline electrolytes. The excellent performance of FeCoS/NF can be attributed to the synergistic effect and amorphous phase of FeCoS as well as the well-defined pine-tree-like array architecture with a large surface area, abundant active sites, and sufficient gas and electrolyte diffusion channels. [Display omitted] • A 3D pine-tree-like structure of FeCoS/NF electrocatalyst was synthesized. • The FeCoS/NF exhibits excellent electrocatalytic activity for OER. • FeCoS/NF-based zinc-air battery shows an open-circuit voltage of 1.27 V. [ABSTRACT FROM AUTHOR]

Doping and morphology tailoring in metal sulfides up to nanoscale plays a vital role for better performance in various applications. Herein hydrothermally synthesized Co-doped nickel sulfide (NiS 2) nanostructures have been transformed from nano-rods to nano-sheets up to optimal doping concentration of 3 %. The phase changes, morphological modifications and elemental investigations have been analyzed by SEM, TEM, HRTEM, SAED, EDS, XRD and FTIR. The morphology transitions revealed that NiCo 3 S exhibited sophisticated morphology of flower like structures formed by nano-sheet patterns. NiCo 3 S electrode possesses an auspicious capacitance of 1242 Fg_1 at 1 Ag_1 within potential window range of 0.1–0.8 V. In accordance with GCD study, CV and EIS study confirmed that NiCo 3 S is more electroactive and less resistive showing excellent stability up to 92 % after 5000 cycles. The power law (b = 0.71) showed the capacitive nature of the NiCo 3 S. The capacitive and diffusive behavior calculated by Dunn's relationship confirmed the pseudocapacitive charge storage behavior of NiCo 3 S electrode making this a potential candidate for electrochemical applications. [ABSTRACT FROM AUTHOR]

The use of loaded co-catalysts has been found to be effective in addressing the issue of rapid recombination of photogenerated carriers, which can limit photocatalytic efficiency. Herein, we report on the adsorption of Ni2+ on the surface of CdS by photodeposition to obtain NiS/CdS composites. It improves visible light response while providing abundant active sites for photocatalytic reaction. NiS/CdS exhibits a superior photocatalytic H 2 evolution rate of up to 7557 μmol·g−1·h−1, which is approximately 4.9 times higher than that of CdS. The corresponding AQE is 19.6% at 420 nm. XPS and photoelectrochemical testing provide a possible mechanism, indicating that the heterojunction between NiS and CdS promotes the transfer and separation of interfacial charge, thus accelerating the water decomposition reaction. This work demonstrates the effectiveness of loading two-dimensional thin film co-catalysts to design high-performance and low-cost composites for promoting the photocatalytic reaction. [Display omitted] • NiS film as co-catalyst is able to reduce the overpotential of hydrogen evolution reaction. • The heterojunction accelerates the transfer and separation of photogenerated carriers. • 20NSCS exhibits highly efficient photocatalytic hydrogen evolution activity and cycling stability. • A possible mechanism for NiS/CdS composite enhanced photocatalytic activity was proposed. [ABSTRACT FROM AUTHOR]

Due to their high energy density and cost‐effectiveness, lithium–sulfur batteries (LSBs) are considered highly promising for the next generation of energy storage technologies. However, the soluble lithium‐polysulfides (LiPSs) notorious for causing the shuttle effect and the sluggish redox kinetics have hindered their practical commercialization. To tackle these challenges, a heterostructural catalyst featuring NiS‐NiCo2O4 interfaces is developed, which serves as an interlayer for LSBs. These interfacial sites leverage the advantages of polar NiCo2O4 and conductive NiS, enabling smooth Li+ diffusion, rapid electron transport, and effective immobilization of LiPSs. This synergistic approach promotes the conversion of sulfur species, resulting in a high discharge capacity of 526 mAh g−1 at 3 C for cells with the NiS‐NiCo2O4 interlayer. Additionally, remarkable cycling stability is achievable with an areal sulfur loading of ≈5.0 mg cm−2. It is believed that this research paves the way for practical applications of LSBs. [ABSTRACT FROM AUTHOR]

Developing low-cost and high-efficiency non-precious metal cocatalysts is the key to the practical application of photocatalysis technology. Here, nickel sulfide (NiS) nanoparticles were synthesized on the surface of strontium titanate (SrTiO 3) via a hydrothermal method, identifying the optimal loading molar concentration of NiS as 10 %. The solar-to-hydrogen efficiency (STH) of 10%NiS/SrTiO 3 :Al was enhanced by 97 times compared to SrTiO 3 :Al and by 1.62 times compared to RhCrCoO x /SrTiO 3 :Al. This improvement is primarily attributed to the metallic-like properties of NiS, which enhance the photocatalyst's light absorption capacity and charge transfer capability. Additionally, the STH value of samples loaded with both NiS and RhCrCoO x reached 0.436 %, indicating a positive synergistic effect in photocatalysis between NiS and RhCrCoO x. Their photocathodic protection capability was also studied in simulated seawater conditions, showing a reduced self-corrosion potential (−0.31V) and a low interface charge impedance (5962 KΩ). This work reveals the potential of NiS as an alternative to precious metal cocatalysts, offering new possibilities for developing cost-effective and high-performance materials for photocatalytic water splitting and photocathodic protection. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate an interface on porous nickel foam (NN) between crystalline nickel sulfide and amorphous nickel sulfide (NNS/NNSx) adapting simple hydrothermal and facile electrodeposition processes, respectively. The developed electrocatalyst required a low overpotential of 15 mV to deliver a current density of 10 mA cm−2 and the interface intrinsically activates the electrocatalyst with an onset overpotential comparable to that of Pt in an alkaline hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

Transition metal chalcogenides have been identified as low-cost and efficient electrocatalysts to promote the hydrogen evolution reaction in alkaline media. However, the identification of active sites and the underlying catalytic mechanism remain elusive. In this work, we employ operando X-ray absorption spectroscopy and near-ambient pressure X-ray photoelectron spectroscopy to elucidate that NiS undergoes an in-situ phase transition to an intimately mixed phase of Ni3S2 and NiO, generating highly active synergistic dual sites at the Ni3S2/NiO interface. The interfacial Ni is the active site for water dissociation and OH* adsorption while the interfacial S acts as the active site for H* adsorption and H2 evolution. Accordingly, the in-situ formation of Ni3S2/NiO interfaces enables NiS electrocatalysts to achieve an overpotential of only 95 ± 8 mV at a current density of 10 mA cm−2. Our work highlighted that the chemistry of transition metal chalcogenides is highly dynamic, and a careful control of the working conditions may lead to the in-situ formation of catalytic species that boost their catalytic performance. Transition metal chalcogenides are effective and economical electrocatalysts for the hydrogen evolution reaction in alkaline media, yet active sites and catalytic mechanisms remain unclear. Here the authors use operando spectroscopy to study the in-situ conversion of NiS to highly active Ni3S2/NiO dual-site catalysts for the alkaline hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

The severe Zn‐dendrite growth and insufficient carbon‐based cathode performance are two critical issues that hinder the practical applications of flexible Zn‐ion micro‐ssupercapacitors (FZCs). Herein, a self‐adaptive electrode design concept of the synchronous improvement on both the cathode and anode is proposed to enhance the overall performance of FZCs. Polypyrrole doped with anti‐expansion graphene oxide and acrylamide (PPy/GO‐AM) on the cathode side can exhibit remarkable electrochemical performance, including decent capacitance and cycling stability, as well as exceptional mechanical properties. Meanwhile, a robust protective polymeric layer containing reduced graphene oxide and polyacrylamide is self‐assembled onto the Zn surface (rGO/PAM@Zn) at the anode side, by which the "tip effect" of Zn small protuberance can be effectively alleviated, the Zn‐ion distribution homogenized, and dendrite growth restricted. Benefiting from these advantages, the FZCs deliver an excellent specific capacitance of 125 mF cm−2 (125 F cm−3) at 1 mA cm−2, along with a maximum energy density of 44.4 µWh cm−2, and outstanding long‐term durability with 90.3% capacitance remained after 5000 cycles. This conformal electrode design strategy is believed to enlighten the practical design of high‐performance in‐plane flexible Zn‐based electrochemical energy storage devices (EESDs) by simultaneously tackling the challenges faced by Zn anodes and capacitance‐type cathodes. [ABSTRACT FROM AUTHOR]

Sulfide all‐solid‐state battery (SASSB) with ultrahigh‐nickel layered oxide cathode (LiNixCoyMn1‐x‐yO2, NCM, x ≥ 0.9) offers the potential of high energy density and safety for superior energy storage systems. However, stable cycling is difficult to realize due to adverse interfacial reactions, space charge layer (SCL), and elemental diffusion. Herein, a straightforward solid‐phase coating strategy is exploited to synthesize Ni90‐S cathode, which greatly improves the charge transmission capability of the composite cathode and suppresses interfacial reactions in SASSB. The consequent SC‐Ni90‐0.2%S/Li6PS5Cl/Li4Ti5O12 SASSB exhibits enhanced electrochemical performance, including a long life of 500 cycles with 87% capacity retention at 1C, high areal capacity of 11.44 mAh cm−2, and excellent rate performance at 20 C. These results promise an efficient strategy for designing cathode materials for SASSBs. [ABSTRACT FROM AUTHOR]

This article reports a simple hydrothermal method for synthesizing nickel disulfide (NiS2) on the surface of fluorine-doped tin oxide (FTO) glass, followed by the deposition of 5 nm Au nanoparticles on the electrode surface by physical vapor deposition. This process ensures the uniform distribution of Au nanoparticles on the NiS2 surface to enhance its conductivity. Finally, an Au@NiS2-FTO electrochemical biosensor is obtained for the detection of dopamine (DA). The composite material is characterized using transmission electron microscopy (TEM), UV-Vis spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The electrochemical properties of the sensor are investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and time current curves in a 0.1 M PBS solution (pH = 7.3). In the detection of DA, Au@NiS2-FTO exhibits a wide linear detection range (0.1~1000 μM), low detection limit (1 nM), and fast response time (0.1 s). After the addition of interfering substances, such as glucose, L-ascorbic acid, uric acid, CaCl2, NaCl, and KCl, the electrode potential remains relatively unchanged, demonstrating its strong anti-interference capability. It also demonstrates strong sensitivity and reproducibility. The obtained Au@NiS2-FTO provides a simple and easy-to-operate example for constructing nanometer catalysts with enzyme-like properties. These results provide a promising method utilizing Au coating to enhance the conductivity of transition metal sulfides. [ABSTRACT FROM AUTHOR]

NiS/Ni@HCNF electrode enable the cell with excellent storage capacity and superior thermal safety performance. [Display omitted] • Catalytic chemistry inspired hollow carbon nanofibers loaded with NiS/Ni is designed. • Such delicate structure shows superior cycling and rate property than many TMSs. • The favorable Li+ storage actions and related reaction kinetics are discovered. • Using the designed structure markedly promotes the thermal safety of LIBs. Transition metal sulfides (TMSs) based anodes hold a very broad application prospect in lithium ion batteries (LIBs). In this work, the catalytic effect of metallic nickel at high temperature was used to generate hollow carbon nanofibers loaded with NiS and Ni (denoted as NiS/Ni@HCNF). The heteroatoms doped carbon fibers buffer the huge volumetric change of NiS during the discharge/charge process, and enhance the ion transport efficiency and electrical conductivity. In addition, the high specific surface area brought by the hollow carbon nanofibers can accelerate the electrolyte penetration and speed up the transport of ions as well as electrons. When used as anode of half cell, this electrode gives 958.5 and 612.9 mAh/g after running 1000 cycles under 1 and 2 A/g, showing the extremely-low attenuation rates of 0.0483 % per cycle and 0.0643 % per cycle, respectively. Impressively, NCM//NiS/Ni@HCNF battery shows the discharge capacity of 187.6 mAh/g at 1st cycle. Regarding the next 100 cycles, the relatively-high discharge capacities (>110 mAh/g) and coulombic efficiency (CE) values (>96 %) are discerned. It is noted that the usage of NiS/Ni@HCNF electrode improves the activation energy for thermal runaway, corroborating the elevated thermal safety of battery. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrochemical water electrolysis is a promising method for sustainable hydrogen production while transiting towards hydrogen economy. Among many, the Anion Exchange Membrane (AEM) based water electrolyzer is an emerging yet potentially affordable technology on maturity for producing large-scale hydrogen accommodating the usage of Non-Platinum Group Metal (non-PGM) based inexpensive electrocatalysts. Herein, we demonstrate the excellent performance of a bifunctional Nickel Copper Phosphide-Nickel sulphide (NCP-NS) electrocatalyst with a unique tensile nanostructure obtained via a facile, controlled ambient galvanic displacement route. An AEM electrolyzer with a larger active area of 10 cm2 stacked with the symmetric NCP-NS electrodes and a membrane demonstrates scalability with a requirement of a mere 1.66 V to reach a current density of 10 mA cm−2. The nickel-copper phosphide boosts the kinetics of charge transfer between the electrode and electrolyte interface, while a unique combination of a few nickel sulphide phases present in the catalyst provides sufficiently appropriate active sites for the overall water electrolysis. For the first time, we report a room temperature performance of ∼ 230 mA cm−2 at 2 V for a non-PGM-based bifunctional electrocatalyst with exceptional durability for over 300 h of operation in an AEM water electrolyser with a retention rate of 95 %-97 % at a current density range of 80–800 mA cm−2. [ABSTRACT FROM AUTHOR]

The metal–organic framework (MOF) materials with significant steadiness and a large specific surface area have been popular with supercapacitor material in recent years. However, its application in supercapacitors is restricted due to the low specific capacitance and poor conductivity. Herein, sulfur compounds with a high theoretical specific capacitance and highly conductive titanium nitride (TiN) were introduced into Co-based metal–organic frameworks/nickel foam (Co-MOF/NF) through a two-step hydrothermal technique (nickel sulfide/titanium nitride@ Co-based metal–organic frameworks/nickel foam). In detail, the fabricated nickel sulfide/titanium nitride@Co-based metal–organic frameworks/nickel foam (Ni3S2/TiN@Co-MOF/NF) electrode material exhibits a markedly high specific capacitance (2648.8 F g−1) at 1 A g−1, compared with that (770 F g−1) of the precursor Co-MOF/NF. And its mass specific capacitance is retained 88.3% (8 A g−1) after 5000 cycles. Furthermore, a non-symmetrical supercapacitor (ASC) composed of Ni3S2/TiN@Co-MOF/NF and AC exhibits excellent power density (801.8 W kg−1) and energy density (97.8 W h kg−1). Therefore, Ni3S2/TiN@Co-MOF/NF with excellent electrochemical properties and stability provides new ideas for the development of excellent supercapacitor electrode materials. [ABSTRACT FROM AUTHOR]

To revolutionize the photochemical efficiency of quantum dots sensitized solar cells (QDSSCs) devices, herein, a passivation of the cells with multilayer material has been developed for heterojunctions TiO2/NiS/MnS/HI-30/Pt devices. In this study, NiS and MnS were deposited on a photoanode for the first time as passivated photon absorbers at room temperature. The adoption of NiS as a passisvative layer could tailor the active surface area and improve the photochemical properties of the newly modified cells. The vibrational shifts obtained from the Raman spectra imply that the energy change is influenced by the surface effect, giving rise to better electronic conductivity. The electrochemical stability and durability test for the N/M-3 device slows down and remains at 8.88% of its initial current after 3500 s, as compared to the N/M-1 device at 7.20%. The disparity in charge recombination implies that both the outer and inner parts of the nanoporous material are involved in the photogeneration reaction. The hybridized N/M-3 cell device reveals the highest current density with a low potential onset, indicating that power conversion occurs more easily because photons tend to be adsorbed easily on the surface of the MnS. The Nyquist plot for N/M-1 and N/M-3 promotes the faster transport of electrolytic ions across the TiO2/NiS/MnS, providing a good interaction for the electrolyte. The I-J Value of 9.94% shows that the passivation with the NiS layer promotes electron transport and enhances the performance of the modified cells. The passivation of the TiO2 layer with NiS attains a better power conversion efficiency among the scant studies so far on the surface passivation of QDSCs. [ABSTRACT FROM AUTHOR]

In the present work, a novel composite of nickel sulfide (NiS) and potato peel‐derived carbon spheres (NiS/PPCS) with higher specific capacitance and cyclic performance was synthesized as electrode material for supercapacitor applications. The composite was deposited on a graphite rod to be use as an electrode. The electrochemical performance studies using CV, GCD, and EIS revealed that the prepared electrode showed an improved current response and higher specific capacitance than the pristine NiS electrode. The maximum specific capacitance for the NiS/PPCS electrode was found to be 2185 F/g at 0.2 A/g current density. More precisely, it was observed that the NiS/PPCS composite exhibited an excellent retention capacity of 95.04% after 20 000 continuous charge‐discharge cycles, showing its exceptional cyclic performance. The impedance studies revealed that the reaction between the NiS/PPCS electrode and electrolyte was rapid and highly reversible. Based on the findings of the electrochemical performances, NiS/PPCS electrode appears to be a potential candidate for highly efficient and economical asymmetric supercapacitors. [ABSTRACT FROM AUTHOR]

Supercapatteries are contemporary electrochemical energy‐storage devices that bridge the gap between the conventional supercapacitors and rechargeable batteries. Supercapatteries utilize battery‐type electrode‐active materials for their charge storage. Among the various futuristic materials, transition‐metal dichalcogenides receive prominent attention due to their excellent charge‐storage capabilities. Herein, the microwave‐assisted hydrothermal synthesis of layered two‐dimensional (2D) nickel sulfide nanosheets (NSN) and their application as electrode‐active materials in high‐performance asymmetric supercapatteries are reported. The layered 2D architecture is preferred for the electrode‐active materials as the layered electrode nanostructure provides a hindrance‐free movement to the electrolyte ions through it during the charge‐storage process that include intercalation/deintercalation mechanisms. The electrochemical thermal stability of the 2D NSN electrode reveals that its stability in KOH (aqueous) electrolyte is better than that in LiOH (aqueous) and NaOH (aqueous) electrolytes. The supercapattery electrode synthesized using 2D NSN exhibits excellent electrochemical charge‐storage performances bearing a maximum specific capacity of 594.77 C g−1 (an equivalent mass‐specific capacitance of 991.29 F g−1) in 2 M KOH (aqueous) electrolyte. The electrochemical cycling performance of the 2D NSN electrode shows a stability over 40 000 cycles without any significant capacity loss. An asymmetric supercapattery device fabricated with 2D NSN electrode as positrode and activated carbon as negatrode exhibits a maximum mass‐specific capacity of 143.58 C g−1 with a corresponding energy density of 29.91 Wh kg−1 in 2 M KOH (aqueous) electrolyte. [ABSTRACT FROM AUTHOR]

Supercapacitors are useful for storing and delivering more energy in smaller footprints. Developing high-energy-density supercapacitors enables more efficient utilization of energy, improved performance, and a means for flexibly addressing diverse energy storage requirements. The electrode materials and the techniques used for their fabrication play a significant role in obtaining the desired operating performance of supercapacitors. The present study employs a novel, simple, scalable, and low-cost fabrication technique to synthesize nickel-cobalt sulfide (NiCo2S4) nanostructures on commercial nickel foam. Prominent morphological and electrochemical characterization techniques were used to assess the structural and operating performance of the synthesized nanostructure. The synergistic effects of nickel and cobalt transition metals resulted in enhanced performance of the nanostructure. The synthesized nanostructure was further employed in a symmetric supercapacitor device. Surface morphological and electrochemical experiments showed an energy density value of 62.8 Wh/kg and retention capacity of 94% even after 8000 cycles. The electrochemical characteristics were validated using electrical experiments as well. The high specific capacitance, faster electron and ion transfer, and improved structural integrity obtained for the supercapacitor indicate its suitability for enhanced energy storage applications. [ABSTRACT FROM AUTHOR]

Poly (3‐methylthiophene) (P3MT) was modified by nickel oxide (NiO) and nickel sulfide (NiS) nanoparticles to enhance its electrochemical performance. The surface influence, crystalline structure, and electrochemical performance of the P3MT/NiO/NiS material were characterized and compared with that of pristine P3MT. It is found that surface modification can improve the structural stability of P3MT without decreasing its available specific capacitance. The electrochemical properties of synthesized P3MT/NiO/NiS electrode were evaluated using cyclic voltammetry and alternating current impedance techniques in 3 M KOH electrolyte. Specific capacitances of 253, 764, 932, and 1434 F g−1 were obtained for P3MT, P3MT/NiO, P3MT/NiS, and P3MT/NiO/NiS, respectively at 5 A g−1. This improvement is attributed to the synergistic effect of Ni2+ ions in the P3MT/NiO/NiS electrode material. The P3MT/NiO/NiS electrode in KOH has average specific energy and specific power densities of 1032 Wh kg−1 and 6192 W/kg, respectively. Only 2% of the capacitance's initial value is lost after 10,000 cycles. The resulting P3MT/NiO/NiS nanocomposite had very stable and porous layered structures. This work demonstrates that P3MT/NiO/NiS nanomaterials exhibit good structural stability and electrochemical performance, and are good material for supercapacitor applications. Highlights: The P3MT/NiO/NiS nanocomposite is fabricated and characterized as supercapacitor electrode.The incorporation of NiO/NiS in the poly (3‐methylthiophene) has improved the electrochemical performance.The P3MT/NiO/NiS electrodes retained 98% of their specific capacitance after 10,000 cycles.The P3MT/NiO/NiS nanocomposite electrode showed specific capacitance of 1434 F g−1 at 5 A g−1.The stability of the nanocomposite was enhanced without altering its morphology and chemical structure. [ABSTRACT FROM AUTHOR]

Facing the situation of nickel resource shortage and increasing nickel demand, it is an important task for the development of nickel industry to realize efficient utilization of low-grade nickel sulfide ore. In this work, the process of NaCl roasting-water leaching was proposed to simultaneously extract valuable metals from low-grade nickel concentrate. Based on the thermodynamic analysis of roasting process, the effect of several key factors on metal extraction was investigated. The results show that the extraction of Ni, Cu and Co can reach approximately 94.08, 92.81 and 91.85 pct, respectively, under the following optimum conditions: temperature 400 °C, time 90 minutes, NaCl dosage 100 pct and concentrate particle size 70–88 µm. The evolution behavior and mechanism of metallic minerals are determined through thermodynamic analysis, differential thermogravimetric analysis, and phase composition analysis of roasted product. The kinetics of the roasting process based on the differential thermal and thermogravimetric experiment was analyzed by Kissinger method and Doyle-Ozawa method. The average apparent activation energy of metallic minerals being chlorinated is determined as 400.12 kJ/mol and the kinetic equation was expressed as d α dt = 2.41 × 10 12 e - 400.12 RT (1 - α) 1.27 . [ABSTRACT FROM AUTHOR]

The cocatalysts play a key role in photocatalytic technology in remarkably improving the efficiency of H 2 evolution. Herein, S vacancies-rich Cd 0.6 Zn 0.4 S nanorods (CZS NRs) were prepared via solvothermal method. Then, as-obtained CZS NRs were modified with Ni–Co PBA-derived NiS x nanoparticles (NPs) cocatalyst using grinding method. The optimized CZS/NiS x -N-1.5 hybrids (CZS/NiS x -N, where N represents nickel nitrate which was used as nickel source) exhibited outstanding stability and activity, the average rate of H 2 was up to 192.82 mmolg−1h−1 in deionized water medium, which was 201.4% higher than that of CZS. Besides, NiS x -A and NiS x -C cocatalysts with different particle sizes were obtained using nickel acetate (A) and nickel chloride (C) as nickel source, respectively. The CZS/NiS x -C-1.5 and CZS/NiS x -A-1.5 exhibited the H 2 evolution rate of 180.70 and 201.93 mmolg−1h−1 in deionized water medium, respectively. The as-prepared materials also exhibited the excellent H 2 evolution performance in natural seawater medium. Besides, the photocatalytic mechanism of H 2 evolution over CZS NRs/NiSs NPs was also discussed. This work develops a novel H 2 evolution cocatalyst and unveils the relationship between the loading amount/particle size of cocatalyst on the H 2 evolution rate. CZS NRs/NiSx NPs hybrids for photocatalytic pure water and natural seawater hydrogen production. [Display omitted] • A novel photocatalytic H 2 evolution cocatalyst was prepared. • Optimized CZS/NiS x exhibits high reusability, and structural stability. • The relationship of loading amount/particle size of cocatalyst on H 2 evolution rate were unveiled. • The evolution process of morphology from Ni–Co PBA NCs to NiS x NPs was explored. • Optimized CZS/NiS x exhibits excellent high activity in deionized water and natural seawater medium. [ABSTRACT FROM AUTHOR]

Water-splitting presents a viable solution to expanding energy needs. To maximise water-splitting performance, transition metal sulphides, a very efficient electrocatalyst, have been extensively researched. It is unable to generate hydrogen (H 2) and oxygen (O 2) because to active sites and weak electrical conductivity. Some carbon-based materials offer superior dispersion capacities and bigger active sites for charge transfer to circumvent these restrictions. This work presents an efficient electrocatalyst combining carbon nanotubes (CNTs) and electrochemically active Nickel sulphides, Ni 17 S 18 (NiS), synthesized by using a wet-chemical approach. The improved electrocatalytic performance of NiS@CNTs can be attributed to higher surface area and higher electrical conductivity of CNTs. Furthermore, linear-sweep voltammetry (LSV) and electrochemical impedance analysis (EIS) were also utilized for the electrochemical investigations. The addition of CNTs to NiS showed a over-potential of 330 mV at 40 mA cm−2, with a Tafel slope of 47 mV dec−1 for OER. Similarly, we have also investigated the HER activity of the as-prepared electrocatalysts at the same current density, having a over-potential of 280 mV with a Tafel slope of 102 mV dec−1. • NiS and NiS@CNTs nanocomposites were synthesized by the precipitation method. • NiS@CNTs exhibits better HER and OER performances as compared to the bare NiS. • NiS@CNT shows Tafel slope 47 and 102 mVdec−1 for OER and HER singly. • Overpotential of 330 mV-OER and 280 mV-HER was reached to current density 10 mAcm−2. [ABSTRACT FROM AUTHOR]

In recent decades, photocatalysis technology, a typical mild and environmentally friendly technique, can use sunlight to drive the oxidation/reduction reactions on the surface of catalysts. However, single semiconductor materials can hardly meet the requirements of photocatalytic application due to the low availability of visible light, quick e− − h+ recombination, and the insufficiency of active sites. Cocatalysts are often introduced to solve the above problems. Among the numerous cocatalysts, NiS cocatalysts exhibit excellent properties, such as superior chemical stability, suitable band structure, and larger specific surface area, which can improve the photocatalytic efficiency of various semiconductors. Herein, the research progress of NiS cocatalysts in photocatalysis is reviewed. First, the structure of NiS and several common preparation methods are briefly introduced. Second, the NiS cocatalytic principle about how to achieve the effective separation of photogenerated carriers is introduced. Third, the methods to optimize the catalytic activity of NiS are mainly summarized. At the same time, the review summarizes the research progress of composite photocatalysts based on NiS cocatalyst. Finally, the review discusses the existing challenges and obstacles of NiS‐based photocatalytic systems and proposes feasible improvements and ideas to meet the future requirements of practical applications. [ABSTRACT FROM AUTHOR]