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Electrochemical decomposition of water to produce hydrogen is an ideal clean fuel that promises to solve problems such as energy depletion and environmental pollution. Transition metal sulfides(TMS M = Fe, Co, Ni) have been widely explored and studied for their potential in oxygen evolution reactions (OER). However, due to their thermodynamic instability, surface reconstruction inevitably occurs during the OER process, forming oxides or (oxygen) hydroxide active species in situ. This process poses a great challenge to reveal the true active sites and the reaction mechanism. Therefore, a fundamental understanding of the catalyst surface reconstruction process is essential for the design of efficient catalysts. To this end, we want to explore the following issues, (1) determine the catalyst activity origin and structural evolution process, (2) clarify the reconstruction mechanism and establish the conformational relationships (3) manipulate the in situ catalyst surface reconstruction through rational modulation strategies. In this review, we summarize and discuss the recent progress of TMS as OER precatalysts, revealing the catalyst reconstruction behavior based on in situ operation techniques, DFT calculations, highlighting the most effective strategies to adjust TMS surface reconstruction.It provides a more comprehensive understanding of the surface reconstruction of TMS, as well as reference for the design and optimization of efficient and stable catalysts. [Display omitted] • Summarized the advances on surface reconstruction of TMS as precatalysts for OER. • Presenting a basic understanding of reconstruction behavior. • Revealed the active origin and catalytic mechanism of surface reconstruction. • The effective regulation of TMS surface reconstruction strategy is highlighted. [ABSTRACT FROM AUTHOR]

Advances in electrochemical interfaces have greatly facilitated the development of new energy systems that can replace traditional fossil fuels. Oxygen evolution reaction (OER) is the core reaction in the new energy conversion system to produce hydrogen. Here, nanorods structure of Mn 3 O 4 /Co 9 S 8 –Ni 3 S 2 /NF-4 was designed and assembled. The Mn 3 O 4 has served as an appropriate matrix to build a composite structure with Co 9 S 8 –Ni 3 S 2 to enhance the stability of catalyst. And the introduction of Mn regulated the electronic structure of Ni and Co, which increased the OER activity of matericals. Further characterization and electrochemical testing have suggested that between polymetallic can effectively optimize conductivity and enhance reaction kinetics. Mn 3 O 4 /Co 9 S 8 –Ni 3 S 2 /NF-4 can achieve overpotential of 188 mV at the current density of 10 mA cm−2 in alkaline solution, with small Tafel slope of 43.2 mV dec−1 and satisfactory stability of 30 h at 10 mA cm−2. This work may show a feasible reference in the design of high-efficient OER catalysts. NF, Co–CHH/NF, Co 9 S 8 –Ni 3 S 2 /NF, Mn 3 O 4 /Co 9 S 8 –Ni 3 S 2 /NF-4The synthesized Mn 3 O 4 /Co 9 S 8 –Ni 3 S 2 /NF-4 electrode exhibited distinguished electrocatalytic performance toward OER in alkaline electrolyte. [Display omitted] • Ultrathin Mn 3 O 4 nanosheets in suit covered on Co 9 S 8 –Ni 3 S 2 nanorods was reported. • Mn 3 O 4 /Co 9 S 8 –Ni 3 S 2 /NF-4 delivers benign performance for OER in alkaline electrolyte. • Large surface area and abundant active sites accelerate electron transfer rate. [ABSTRACT FROM AUTHOR]

The intent of designing and exploring novel active electrode materials is to enhance the electrochemical performance of supercapacitors. Herein, a hierarchical structure of nickel-cobalt-sulfide nanostructures (NiCo 2 S 4) decorated on the electrospun N -doped carbon nanofiber (CNF), NiCo 2 S 4 @CNF, is manipulated using a one-step and simple hydrothermal approach. The fabricated hierarchical structure of the NiCo 2 S 4 @CNF is featured by a large surface area and a high porosity that serve as ion diffusion channels. Therefore, it manifests high specific capacitance and specific capacity values of 377.2 C g−1 and 754.4 F g−1 at a current density of 1 A g−1, respectively. Furthermore, a NiCo 2 S 4 @CNF//CNF hybrid supercapacitor in which a positive electrode of NiCo 2 S 4 @CNF is assembled with a negative electrode of CNF to estimate the electrochemical performance of the NiCo 2 S 4 @CNF. As a result, the device has a superior energy density of 65.6 and 52.5 Wh kg−1 at a power density of 665 and 1313.8 W kg−1, respectively. Moreover, the device reveals good stability with capacitance retention of 72% after 3000 charge/discharge cycles. These outstanding results enable the designed hierarchical structure of the NiCo 2 S 4 @CNF to be a promising electrode material for supercapacitors (SCs) applications. [Display omitted] • The hierarchical structure of NiCo 2 S 4 @CNF was prepared to be used as an efficient electrode for a hybrid supercapacitor. • NiCo 2 S 4 @the electrospun N -doped CNF has a higher surface area and a high porosity that serves as ion diffusion channels. • NiCo 2 S 4 @CNF hierarchical structure exhibited a specific capacitance of 754.4 F g−1 at a current density of 1 A g−1. • NiCo 2 S 4 @CNF//CNF hybrid supercapacitor showed specific energy of 65.6 W h kg−1 at a specific power of 665 W kg−1. [ABSTRACT FROM AUTHOR]

Numerous studies have focused on the preparation of carbon fibers (CFs)-based high-efficiency microwave absorbers with reasonable structural design and surface morphology control, which simultaneously meet the required impedance matching and loss ability. Here, CFs@NiS/Ni 3 S 4 @MoS 2 (CNNM) with core-sheath structure was prepared through several simple hydrothermal reactions. The morphology of the as-prepared CNNM nanocomposite is controlled by the amount of added sodium molybdate dihydrate, which causes the difference in minimum reflection loss (RL) and effective attenuation bandwidth among the samples. For the microwave absorbing performance, the minimum RL is −18 dB and the effective attenuation bandwidth is 8.7 GHz, which appear at the thickness of 2.8 mm and cover most of the X- and Ku-bands. The excellent absorbing performance is attributed to optimized impedance matching and enhanced polarization loss. These results originate from the transition metal sulfides, which not only effectively prevent the skin effect by decreasing the conductivity of CFs but also increase interfaces and flaws, leading to interface polarization and dipole polarization losses. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mechanisms of PMS activation and TC degradation by four TMS were compared. • FeS/PMS: adsorption & Fe(IV) = O; CoS/PMS: Co(IV) &1O 2 ; CuS/PMS: • OH, SO 4 •− , O 2 •− , 1O 2. • MnS/PMS: adsorption, reduction by sulfur species & oxidation by ≡Mn(III)OOSO 3. • S vacancies mediate Fe cycling; S species mediate metal valence cycling and/or TC reduction. • Wide pH adaptability and an anti-interference ability to Cl−, SO 4 2− and NO 3 − Advanced oxidation processes (AOPs) are promising treatment options for environmental remediation to reduce chemical oxygen demand (COD) and emerging contaminants. Transition metal sulfides (TMSs) are a class of common catalysts in AOPs, but actually, they also widely exist in the environment in the form of sulfide minerals and seriously contaminated water bodies as black-odorous substances. Therefore, it is crucial to find out their roles during water decontamination using AOPs. This study investigated different mechanisms and performance of four common TMSs (FeS, CuS, CoS and MnS) in peroxymonosulfate (PMS)-based AOPs for the removal of a representative micropollutant tetracycline (TC). The results showed that CoS/PMS was the most efficient with 100 % TC removal within 1 min, followed by FeS/PMS (100 %, 10 min) with the apparent rate constant (k obs) of 0.45 min−1. TC removal by CuS (k obs = 0.10 min−1) and MnS (k obs = 0.02 min−1) took 30 min with 96 % and 82 % removal, respectively. Interestingly, the dominant reactive species were different in these systems, i.e., high-valent iron (Fe(IV)) in FeS/PMS, mainly radicals (• OH, SO 4 •− , O 2 •−) and singlet oxygen (1O 2) in CuS/PMS, and Co(IV) and 1O 2 in CoS/PMS. In comparison, TC was removed in MnS/PMS mainly through cooperative adsorption, reduction and oxidation by MnS. Low valent sulfur species, such as S2− and S 2 2−, may participate in the valence cycles of metals or TC reduction. The above four systems had a wide pH (3.6–11.1) adaptability and a strong anti-interference ability to co-existing Cl−, SO 4 2− and NO 3 −, but could be hindered by CO 3 2−, PO 4 3− and humic acid. This study provides novel insights into the TMS-based catalysts in AOPs, which will pave the way for advancing AOP technology. [ABSTRACT FROM AUTHOR]

• A simple and efficient route for the synthesis of 3D heterostructures is proposed. • The synergistic effect between the components improves the activity of the material. • This 3D heterostructured catalyst exhibits outstanding electrocatalytic performance. 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 MoS 2 -FeCoS 2 -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 (η 10 = 176 mV) and OER (η 10 = 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. [Display omitted] [ABSTRACT FROM AUTHOR]

This work presents the fabrication of a novel CeVS 3 /rGO nanocomposite using an easy hydrothermal route for supercapacitor applications. Physical studies revealed that CeVS 3 showed flakes-like morphology, which is successfully decorated on reduced graphene oxide (rGO) sheets in nanocomposite. The electrochemical studies exhibited that fabricated CeVS 3 /rGO showed improved capacitive behavior with notable specific capacitance (C s) of 1516 F/g at 1 A/g current density (j d) as well as excellent rate capability due to combined effect of CeVS 3 nanoflakes and rGO sheets. Nanocomposite also demonstrated a lower resistance of 0.21 Ω than pure material, which have a charge transfer resistance (R ct) of 0.48 Ω. Furthermore, a two-electrode symmetric study was carried out in KOH solution (2.0 M), demonstrating a specific energy (S E) of 18.73 Wh/kg and specific power (S P) of 264.5 W/kg with remarkable cyclic stability after 5000 cycles. These findings demonstrated that innovative CeVS 3 /rGO can be utilized in next-generation supercapacitor applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Transition metal sulfides (TMSs) have become promising candidates as electrode materials in energy storage fields thanks to the high theoretical capacity. However, their application is hindered by depressed electrical conductivity and poor cycling performance. Herein, we proposed a ZIF-67 derived, nitrogen-doped, graphene-coated and carbon nanotubes-interlinked 3D Co 3 S 4 /C conductive network (N–Co 3 S 4 -GN/CNT) for high-performance supercapacitors. Through controlling the mass ratio of ZIF-67, melamine and g-C 3 N 4 , various microstructures with determined electrochemical performance could be achieved. The nanocomposites synthesized with the ingredient mass ratio of 2: 1: 1 (NCSC-211) were proven to have the most excellent comprehensive electrochemical properties. In the NCSC-211 nanostructure, multi-layer graphene function as conductive shells for improved cycling performance by alleviating pulverization caused by volume change, thick CNTs act as conductive bridges and agglomeration spacers that increase electron conductivity and provide more active sites for redox reaction and doped-nitrogen offer enhanced wettability to electrolyte and faster electron transfer. The NCSC-211 electrode displayed specific capacitance of 1158 F g−1 at 1 A g−1, rate capability of 86% at 10 A g−1 and extraordinary cycling stability with 97.2% capacitive retention after 4000 cycles. Furthermore, the assembled asymmetric supercapacitor NCSC-211//activated carbon exhibited energy density of 43.73/37.69 Wh kg−1 at power density of 800/8000 W kg−1 and capacity retention of 95.3% after 5000 cycles at 5 A g−1. The designing strategy of in-situ grown instead of additional added conductive phase that fully-covered and strongly-interlinked network nanostructure may pave the road towards TMSs in synthesizing energy storage materials by compensating their intrinsic drawbacks. The N–Co 3 S 4 -GN/CNT 3D interlinked conductive network nanostructures were rationally designed and successfully synthesized as electrode materials for supercapacitors. The NCSC-211 electrode exhibited the most comprehensive electrochemical performance especially long cycle life, which thanks to the in-situ grown multi-layer graphene shells as well as thick carbon nanotubes bridges and spacers. [Display omitted] • Construction of N–Co 3 S 4 -GN-CNT 3D interlinked conductive network nanostructure. • The graphene and carbon nanotubes are in-situ grown instead of additional synthesized and further composited. • Tightly-coated graphene conductive shells restrain volume expansion of Co 3 S 4 nanoparticles. • Strongly-interlinked CNTs conductive bridges and agglomeration spacers increase electrical conductivity and active sites. • Extraordinary cycling stability with 97.2% capacitance retention after 4000 cycles for cobalt sulfide electrode materials. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) as self-sacrificing templates for high-performance supercapacitor electrode materials have garnered significant attention. In this study, the core-shell multi-heterojunction array of NiCo-LDH@NiCoS@NiMnS was synthesized for the first time using a NiCo-MOF template through hydrothermal growth, followed by ion substitution etching and controlled sulfidation. The NiCo-LDH@NiCoS@NiMnS core-shell multi-heterojunction boasts a hierarchically porous framework, multi-component synergy, and robust structural stability, which together provide abundant redox active sites and facilitate rapid reaction kinetics. Consequently, the self-supporting NiCo-LDH@NiCoS@NiMnS porous electrode achieves a specific capacitance of 9.31 F cm−2 (1862 F g−1) at 8 mA cm−2 (1.6 A g−1) and demonstrates excellent rate performance (52 %, 8–50 mA cm−2). The assembled NiCo-LDH@NiCoS@NiMnS//AC asymmetric supercapacitor (ASC) exhibits an energy density of 88.9 Wh kg−1 at 323.5 W kg−1, maintaining an energy density of 49.7 Wh kg−1 even at a power density of 4043 W kg−1. It retains 90 % of its capacitance after 6000 cycles at 16 mA cm−1. Notably, two ASC devices in series can power an LED light for over 30 minutes. These results confirm that the MOF self-sacrificing template method and controllable sulfidation strategy are effective for designing electrode structures in electrochemical energy storage. [Display omitted] • The NiCo-LDH@NiCoS@NiMnS core-shell multiple heterojunctions array electrodes are synthesized. • The porous heterojunction framework shows good structural stability and fast reaction kinetics. • The synergistic effect between the multi-components improves the energy storage performance. • A hybrid supercapacitor delivers an energy of 49.7 Wh kg−1 at 4043 W kg−1. [ABSTRACT FROM AUTHOR]

The over-exploitation of antibiotics in food and farming industries ruined the environmental and human health. Consequently, electrochemical sensors offer significant advantages in monitoring these compounds with high accuracy. Herein, MOF-derived hollow Co 3 S 4 @MoS 2 (CS@MS) heterostructure has been prepared hydrothermally and applied to fabricate an electrochemical sensor to monitor nitrofuran class antibiotic drug. Various spectroscopic methodologies have been employed to elucidate the structural and morphological information. Our prepared electrocatalyst has better electrocatalytic performance than bare and other modified glassy carbon electrodes (GCE). Our CS@MS/GCE sensor exhibited a highly sensitive detection by offering a low limit of detection, good sensitivity, repeatability, reproducibility, and stability results. In addition, our sensor has shown a good selectivity towards the target analyte among other potential interferons. The practical reliability of the sensor was measured by analyzing various real-time environmental and biological samples and obtaining good recovery values. From the results, our fabricated CS@MS could be an active electrocatalyst material for an efficient electrochemical sensing application. [Display omitted] • CS@MS heterostructure was fabricated for the electrochemical detection of FZ. • The proposed sensor has shown excellent low LOD and sensitivity values. • Our sensor displayed remarkable selectivity, performance, and stability results. • CS@MS sensor monitored FZ in multiple real-world samples good with recovery values. [ABSTRACT FROM AUTHOR]

Developing lower-cost and higher-efficient photocatalysts is still a major challenge for the solar to hydrogen energy conversion by photocatalytic water splitting. Herein, P-doped Co 9 S 8 (P–Co 9 S 8) was synthesized by a hydrothermal process using low-cost RP as raw material, and then P–Co 9 S 8 was employed to construct heterojunction with g-C 3 N 4 via a mechanical-mixing method. Investigation shows that P–Co 9 S 8 can not only improve the electrical conductivity and surface area of the composite, but also can lower the over-potential of H 2 evolution, leading to an enhanced H 2 evolution kinetics. The H 2 evolution rate of resultant 25% P–Co 9 S 8 /g-C 3 N 4 reached 4362 μmol g−1 h−1 under UV and visible light, being nearly 121.2 times higher than that of g-C 3 N 4. The charge transfer between P–Co 9 S 8 and g-C 3 N 4 follows the Type-I route based on the photoelectrochemical analysis, leading to more electrons on the conduction band of P–Co 9 S 8 to participate the H 2 evolution processes. This work provides a new way for preparation of P-doped sulfides with potential applications in the field of photocatalysis. • P-doped Co 9 S 8 nanospheres was successfully fabricated via a facile hydrothermal method. • P-doped Co 9 S 8 was first employed in photocatalytic hydrogen evolution from water splitting. • H 2 evolution rate of 25% P–Co 9 S 8 /g-C 3 N 4 composite is 121.2 times higher than that of g-C 3 N 4. • The charge transfer between P–Co 9 S 8 and g-C 3 N 4 follows the Type-I route during the reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Screening of Transition metal sulfides on HY catalysts for SRO of decalin was performed. • Comprehensive GCxGC gives a unique molecular insight of SRO reaction. • A new reaction scheme has been proposed. • New ternary systems efficient at medium temperature are proposed. Bifunctional catalysis combining acidic catalysts and sulfide active phases is usually related to hydrocracking catalysts which balances the hydrogenation function of a NiMo (NiW) alumina supported sulfide catalysts and the acidic function of a zeolite. The discovery of sulfur-resistant catalysts for selective ring opening (SRO) is an important challenge for refiners, considering the future legislation on cetane index of diesel fuels. In the present work, we studied the properties of various transition metal sulfides (TMS) supported on Y zeolite in gas-phase decalin hydroconversion at high hydrogen pressure (5 MPa) in the presence of 0.8 % H 2 S concentration. This screening shows high activities for noble metal based sulfides with a mechanism which proceeds by skeletal isomerization induced by the zeolite. Catalytic activity was improved by the use of ternary sulfides such as Ni 1-x Ru x S 2 or NiRh 2 S 4 on Y zeolites. High decalin conversion levels can be reached below 250 °C with more of 20 % of ring opening products and thanks to the use of comprehensive GC, a detailed mechanism of the SRO of decalin is given. [ABSTRACT FROM AUTHOR]

Nowadays, rational yet high value-added utilization of low-cost petroleum asphalt still faces a significant challenge. In light of its high carbon content and abundant sulfur atoms, here, an in-situ bonding sulfur strategy is proposed to fabricate transition metal (Mn, Mo, Fe, or Co)-based/carbon composites (TM-based/C). This strategy successfully achieves the conversion from thiophenic-S of asphalt into transition metal sulfides (TMSs). When tested as anodes for lithium-ion batteries (LIBs), the TM-based/C electrodes deliver better specific capacity and cycling performance than those of sulfur-doped carbon nanosheets (SCN) electrode. As a typical example, a 3D network-nanosheets structure of Mn-based/C composite is constructed, and the optimized MnO 2 /MnS 2 /C-2 electrode achieves low charging/discharging voltage platform of 1.2 V/0.58 V, and delivers long-term life of 827 mAh g−1 after 400th cycle at 0.5 A g−1. These excellent electrochemical properties benefit from its structural integrity upon cycling and the formation of MnS 2 /MnO 2 phases. Furthermore, LiFePO 4 /(MnO 2 /MnS 2 /C-2) full cell exhibits a remarkably reversible capacity of 168 mAh g−1 at 0.8C, and impressive cycling stability of 78% after 400 cycles at 1 C, better than those of LiFePO 4 /(commercial graphite). This work may provide a new perspective for the high value-added utilization of low-cost petroleum asphalt for efficient anodes toward LIBs. An in-situ bonding sulfur strategy converts thiophenic-S of asphalt to transition metal sulfides, forming transition metal-based/carbon (TM-based/C) composites. TM-based/C electrodes deliver better specific capacity and cycling ability, and the LiFePO 4 /(MnO 2 /MnS 2 /C-2) full cell exhibits a remarkably reversible capacity. [Display omitted] • High value-added utilization of low-cost petroleum asphalt is achieved. • The thiophenic-S of asphalt is converted into transition metal sulfides. • A 3D network-nanosheets structure of MnO 2 /MnS 2 /C-2 composite is constructed. • Transition metal-based/carbon electrodes deliver excellent rate and cycling performance. • LiFePO 4 /(MnO 2 /MnS 2 /C-2) full cell exhibits impressive cycling stability of 78% after 400 cycles. [ABSTRACT FROM AUTHOR]

The development of nanomaterials that mimic oxidase-like activities has recently attracted an increasing amount of attention. Obtaining highly active and cost-effective oxidase mimics has posed a significant challenge in this area of research. In this study, we successfully synthesized nickel-doped ferrous disulfide nanocubes (Ni–FeS 2) via a facile one-step method. Characterization by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that Ni was predominantly distributed within the surface layer of the Ni–FeS 2 nanocubes. The incorporation of nickel in density functional theory (DFT) calculations effectively reduced the d-band center of Fe, resulting in weakened adsorption to intermediates and thereby enhancing its catalytic efficiency. Moreover, we developed a novel approach based on Ni–FeS 2 (the Ni–FeS 2 method) for detecting reducing substances, which exhibited good sensitivity toward ascorbic acid (AA), glutathione (GSH), and cysteine (Cys). Remarkably, the established Ni–FeS 2 method was successfully employed for in vitro assessment of total antioxidant capacity (TAC) in cellular and organ samples, thereby enabling discrimination between normal, senescent, and malignant cells as well as distinguishing among healthy liver tissue, cancerous liver tissue, and metastatic organs. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Electronic structure modulation of the Ni active site in the NiFeS via metal doping. • Cr significantly induces the formation of oxyhydroxide, followed by Ti, V, and Ag. • Ti accelerates the reaction kinetics, followed by Ag, Cr, and Zn. • Ti effectively modulates the CO 2 adsorption energy, giving facile CO 2 desorption. • NiFeTiS exhibits an excellent UOR potential of 1.36 V at 100 mA cm−2. Enhancement of urea oxidation reaction (UOR) activity of NiFe sulfide via metal doping, including V, Zn, Cr, Ag, and Ti, is demonstrated. X-ray photoelectron and absorption spectroscopy analyses show different degrees of electronic structure modulation of the Ni site due to the doping of the third metals having different t 2g and e g occupancies. Cr reduces the energy needed for the in-situ formation of the oxyhydroxide, followed by Ti, V, and Ag. The reaction kinetics is accelerated by Ti, followed by Ag, Cr, and Zn. Ti also optimizes the d-band center and CO 2 adsorption energy, which is supported by density functional theory calculation. Self-reconstructed sulfate-containing oxyhydroxide during UOR is demonstrated via in-situ Raman and post-transmission electron microscopy analyses. The sulfate is also found to affect the potential required for the formation of the oxyhydroxide. The optimized NiFeTi-containing sulfide exhibits an excellent UOR potential of 1.36 V at 100 mA cm−2 and is stable up to 80-h. This work provides a strategy and deep understanding in enhancing UOR performance of sulfide catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of NiMnS/carbon fibers (CFs) was made as anodes by regulating Ni/Mn ratio. • NiMnS/CFs delivered the final discharge capacities of 730 mA h g−1 at 0.1 A g−1. • After 250 cycle, NiMnS/CFs exhibited 99% of capacity retention at 1 A g−1. • DFT predicts fast charge–discharge rate with low diffusion energy barrier for Li+. • NiMnS/CFs-based full cell shows a specific energy 529 W h kg−1 and stable durability. Transition metal sulfides (TMSs) have been appraised as promising anode materials for lithium-ion batteries (LIBs), however, the average conductivity and drastic pulverization produced by specific volume variation during discharge–charge cycles limit their practical application. To resolve these critical issues, an in-situ fabrication approach has been utilized to develop binary TMS-embedded carbon nanofibers (CFs) by regulating the loading of metallic (cationic) components. Herein, a series of NiMnS/CFs-n composites was prepared by controlling Ni/Mn feeding ratios (n) via successive electrospinning, carbonization and sulfidation method. The inventive engineering procedure provides excellent durability (∼99 % compared to 2nd cycle) up to 250 cycles at 1 A g−1 and superb rate performance for NiMnS/CFs-2.0 anode. The final discharge capacities of NiMnS/CFs-2.0 are 730, 608, 562, 468, 370, and 306 mA h g−1 at 0.1, 0.3, 0.5, 1, 3, and 5 A g−1, respectively. Theoretical calculations enable us to understand the role of typical Ni/Mn feeding ratio on electronic properties and confirm that the hybrid NiMnS/CFs-2.0 surface provides enhanced material conductivity, improved Li adsorption energies for S-top sites, and fast discharge–charge rate with low diffusion energy barrier. Meanwhile, the full-cell containing NiMnS/CFs-2.0 anode outperforms the commercialized graphite anode with a high specific energy of ∼529 W h kg−1 and stable durability, which also successfully enlightens a light bulb. The present study will provide a scalable and simple method to fabricate the integrated composite of binary TMS/CFs by proper cationic regulation and offer useful guidelines for commercial applications of TMS-based anode. [ABSTRACT FROM AUTHOR]

The transition metal sulfides have gained extensive interest in energy storage devices owing to their unique features. However, the research-based on cobalt, copper and manganese sulfide composites is limited while they are considered as promising contenders for supercapacitor electrodes. The simplest and facile one-step electrodeposition technique was adopted for the direct growth of CuMnS and CoMnS on a Ni-substrate. The electrochemical properties of CuMnS and CoMnS electrodes were investigated and maximum specific capacitances of 1691 and 2290 F/g, respectively, were obtained at 10 A/g current density. Further, these electrodes are investigated with activated carbon (AC) electrode to fabricate asymmetric supercapacitor devices where CoMnS//AC exhibited superior energy density values than CuMnS//AC device. However, both the devices show a relatively uniform capacitance retention rate (~94%) after 2500 charging-discharging cycles. Furthermore, the role of capacitive- and diffusive-controlled contributions in the charge storage phenomenon of supercapacitor devices are explicitly scrutinized by employing Dunn's model. Co-electrodeposition of transition metal sulfides has great potential as electrode material for highly effective supercapacitor devices. [ABSTRACT FROM AUTHOR]

A cost-effective counter-electrode based on the NiCo 2 S 4 /carbon nanofibers (NiCo 2 S 4 @C/CNFs) has been synthesized by a combined two-step process of electrospinning and hydrothermal method. With NiCo 2 S 4 @C/CNFs nanocomposite as counter electrode, the dye-sensitized solar cells can deliver an overall power conversion efficiency of 9.00% at 100 mW cm−2 illumination (AM 1.5G), which is significantly higher than 7.48% of the expensive Pt counterpart. • Electrospun and hydrothermal techniques were used to synthesize NiCo 2 S 4 /CNFs. • The NiCo 2 S 4 /CNFs composite was used as counter electrode in DSSCs for the first time. • The DSSCs based on NiCo 2 S 4 /CNFs that achieved a PCE of 9.00%. Possing excellent catalytic performance about counter electrode (CE) is the prerequisite for obtaining high performance dye sensitized solar cells (DSSCs). Herein, The NiCo 2 S 4 /carbon nanofibers (NiCo 2 S 4 /CNFs) are successfully synthetised via hydrothermal and electrospinning method, and then directly used in DSSCs. Owing to the synergistic effect between the catalytic of NiCo 2 S 4 materials and the electrical conductivity of CNFs, All chemical measurements reveal that NiCo 2 S 4 /CNFs applied in DSSCs exhibit good power conversion efficiency (9.0%) and stability, which surpass that of DSSCs with Pt CE (7.48%), indicating that NiCo 2 S 4 /CNFs composite would be helpful for the low-cost and efficient application of DSSCs. [ABSTRACT FROM AUTHOR]

High-activity and cost-effective transition metal sulfides (TMSs) have attracted tremendous attention as promising catalysts for hydrogen evolution reaction (HER). However, a significant challenge is the simultaneous construction of abundant electrochemical active sites and the fast electronic transmission path to boost a high-efficient HER. Herein, we demonstrate a facile one-step hydrothermal preparation of MoS 2 hollow nanospheres decorating Ni 3 S 2 nanowires supported on Ni foam (NF), without any other additional template, surfactant or annealing. In this three-dimensional (3D) heterostructure, the ultrathin-layered MoS 2 hollow nanospheres contribute to the promotion of the total surface area and the electrochemical active sites. Meanwhile, the Ni 3 S 2 nanowires are beneficial to the high electrical conductivity. Consequently, the optimized MoS 2 /Ni 3 S 2 /NF-200-24 electrocatalyst presents an extremely superior HER activity to that of individual MoS 2 /NF and Ni 3 S 2 /NF. The HER overpotentials are 85 mV at 10 mA cm−2 and 189 mV at 100 mA cm−2, which are also comparable with the state-of-the-art 20% Pt/C/NF electrode at both low and high current. Ultrathin-layered MoS 2 hollow nanospheres decorating Ni 3 S 2 nanowires self-supporting electrode were synthesized via the one-step hydrothermal route. It exhibited the excellent electrocatalytic activity and stability for hydrogen evolution reaction. Image 1 • MoS 2 hollow nanospheres decorating Ni 3 S 2 nanowires by one-step hydrothermal route. • Extensive activity sites on MoS 2 hollow nanospheres and MoS 2 /Ni 3 S 2 interfaces. • Excellent HER activity (η = 85 mV at 10 mA cm−2 and η = 189 mV at 100 mA cm−2). [ABSTRACT FROM AUTHOR]

The development of high-performance anode materials for lithium-ion batteries is a critical aspect of advancing energy storage technology. This study presents a novel approach to improve the charge capacity of anodes by harnessing the reversible growth of the solid electrolyte interface (SEI). This work focuses on cobalt sulfide (Co 9 S 8) nanoparticles incorporated into a porous carbon nanotube (CNT) structure. Through a two-step pyrolysis process, Co 9 S 8 CNT composites, characterized by their conductive and mechanically robust CNT matrix are successfully synthesized. These Co 9 S 8 CNT anodes exhibit excellent initial charge capacity (560.5 mAh g−1 at 100 mA g−1) and remarkable stability, with a charge capacity of 633 mAh g−1 after 1000 cycles at 1000 mA g−1, accompanied by a Coulombic efficiency exceeding 99 %. Notably, this investigation reveals that the growth of the SEI plays a pivotal role in enhancing the charge capacity. Through in-situ Raman spectroscopy and other analytical techniques, it is suggested that the reversible reduction of organic solvent molecules within the large polymeric SEI is responsible for the increased charge capacity. This unique phenomenon is characterized by changes in the SEI's composition, driven by the charge and discharge processes. This study is a novel attempt to report a SEI's reversible growth that results in improved charge capacity, contrasting with prior research where SEI growth typically leads to capacity loss. Understanding this stable system provides valuable insights into increasing the cycle life and charge capacity of anodes, not only for transition metal sulfides but also for broader applications in energy storage. [ABSTRACT FROM AUTHOR]

Lithium-sulfur batteries are regarded as one of the most promising next-generation energy storage systems due to their high theoretical volumetric and high weight energy density. However, there are severe problems in the application of lithium-sulfur batteries. The shuttle effect of soluble lithium polysulfide (LiPs) and the low conductivity of sulfur, which leads to slow redox kinetics, are hindering the more significant application of lithium-sulfur batteries. One of the viable solutions to the cathode problem of lithium-sulfur batteries is heterostructured materials. The built-in electric field provided by the heterostructure can significantly accelerate the kinetics of charge transport. In this work, we constructed a heterogeneous structure of G-VS 4 /MoS 2 composites(PVM) modified by Polyvinylpyrrolidone(PVP) is constructed based on graphene, which consists of VS 4 nanosheets and MoS 2 nanosheets grown vertically on graphene lamellae. With weak van der Waals interactions, the one-dimensional (1D) chain-like VS 4 crystal structure enables fast charge transfer in Li-ion batteries. The two-dimensional (2D) lamellar MoS 2 crystals contain Mo-S bonds that also have adsorption effects on polysulfides. Density functional theory (DFT) calculations show that VS 4 and MoS 2 can increase the binding energy of the anode to the polysulfide. Therefore, the S@PVM cathode material provides a large capacity of 1061.4 mAh/g at 0.5 C and can still get to 808.3 mAh/g after 400th cycles. A capacity retention rate of 76.15% is obtained at the same time. It can also boast an initial discharge capacity of 834.8 mAh/g at 1 C. These works can provide more thoughts for developing cathode materials for lithium-sulfur batteries. • G-VS 4 /MoS 2 heterostructures composite was prepared by hydrothermal method modified by Polyvinylpyrrolidone(PVP). • The composite electrode achieves impressive initial capacity and long cycle stability at 0.5 C and 1 C. • The composite electrode can inhibit the shuttle effect effectively and achieve fast electrochemical reaction kinetics. • The composite electrode achieves long cycle stability with a high sulfur loading of 4.6 mg cm−2. [ABSTRACT FROM AUTHOR]

[Display omitted] • MS 2 (M = Fe, Ni, Co) have been synthesized by hydrothermal and calcining process. • First electrochemical comparison of MS 2 cathodes in Aluminum ion battery system. • CoS 2 had Co2+/Co3+ involved in charge compensation in addition to S 2 2−/S2−. • First-principles calculations revealed different Al ion storage mechanisms in MS 2. Transition metal dichalcogenides (TMDs) featured an open framework structure and versatile electronic properties are attractive for their higher capacitance when used as cathodes for aluminum-ion batteries (AIBs). However, the inexhaustive understanding of cell chemistry involving complicated charge transfer stalls the deployment of this type AIBs electrode materials. Here the sulfide materials of MS 2 (M = Fe, Ni, Co) served as emblematic conversion-type electrodes are taken as models to shed light on the regularity among the Al storage mechanisms in TMDs cathodes. To explain such chemistry, we therefore interrogate the redox mechanisms between MS 2 (M = Fe, Ni, Co) from a broad range of experimental and mechanistic characterization perspectives. Remarkably, as indicated by characterization results, the detailed Al insertion and removal processes occurring in MS 2 (M = Fe, Ni, Co) cathodes are revealed, accompanied by the anionic-redox reaction of sulfide anion (S2−), whereas the valence state transitions of the metal element in CoS 2 (Co2+∼Co3+) also occur simultaneously during the insertion/extraction of Al3+. Using theoretical calculations, we further clarify the essential reasons for the mechanistic discrepancy, and discuss the energy storage regularity in TMDs. These foundations not only contribute to a profound understanding for the charge storage mechanisms in TMDs but also expand the palette of property boosting electrode materials for practical AIBs. [ABSTRACT FROM AUTHOR]

Transition metal sulfides have recently captured the utmost attention as an energy storage device owing to their excellent electrochemical activity and conductivity. The amalgamation of carbonaceous materials along with transition metal sulfides was found to do wonders in the field of supercapacitors by amplifying the surface area, conductivity, capacitance, and stability of the active electrode material. In the present work microflower like CuS and CuS/C-dots composite was synthesized via the facile hydrothermal method. Numerous characterization techniques like XRD, SEM, TEM, XPS, and EDS were used to study the properties of the as-prepared samples. The CuS/C-dots composite as an active anode material exhibited an outstanding electrochemical performance with a superior specific capacitance of 2642 Fg−1 at a current density of 2 Ag−1. Furthermore, CuS/C-dots composite material displayed excellent capacitance retention of 58 % after 2000 cycles at a current density of 10 Ag−1. The superior charge transfer kinetics, unique structure, and conductivity of CuS/C-dots composite make it a remarkable material for electrochemical energy storage devices. [Display omitted] • CuS/C-dots microflowers were synthesized by one-step hydrothermal method. • The composites exhibited greater electrochemical performance than pristine CuS. • CuS/C-dots electrode displayed an outstanding specific capacitance of 2642 Fg−1 at 2 Ag−1. • Exceptional capacitance retention of 58 % after 2000 cycles at 10 Ag−1 and superior coulombic efficiency of 99.44 %. [ABSTRACT FROM AUTHOR]

[Display omitted] • The FeOOH-Co 9 S 8 heterostructure was prepared by a simple and stable synthetic method. • The FeOOH-Co 9 S 8 heterogeneous interface modulates the electronic structure of the Co site, facilitating the conversion of *O to *OOH and lowering the energy barrier of the OER reaction. • The obtained FeOOH-Co 9 S 8 composite electrode has excellent OER activity with an overpotential of 215 mV at a current density of 100 mA cm−2. The oxygen evolution reaction (OER) is a four-electron–proton coupling process with a high kinetic energy barrier, which affects the overall efficiency of water splitting. Rational construction of specific interfaces and optimization of electron interactions can effectively promote the kinetic behavior of OER. Herein, ultrathin FeOOH nanosheets were loaded on Co 9 S 8 nanorods by hydrothermal method to construct heterogeneous structures (FeOOH-Co 9 S 8 /NF), and the modulation of catalytic activity by structural changes in the phase interface region was investigated. FeOOH-Co 9 S 8 /NF showed excellent performance as an OER catalyst, requiring an overpotential of only 215 mV to reach 100 mA cm−2. The rich heterogeneous interface can optimize the coordination environment of the Co site by redistributing the interfacial charge to obtain the appropriate chemisorption strength of oxygen-containing intermediates. This paper explores the relationship between interfacial electronic structure changes and catalyst performance enhancement, and provides an experimental basis for further practicalization of OER catalysts. [ABSTRACT FROM AUTHOR]

A Mott–Schottky (MS) heterojunction of CoS 2 /NiS 2 embedded in a carbon matrix is successfully synthesized to form a high sodium storage CoS 2 /NiS 2 @C anode material for sodium-ion batteries. The underlying mechanism for performance enhancement are investigated by both in/ex-situ measurements and DFT calculations. This research has taken an important step towards the development of high-performance electrode materials for sodium-ion batteries. [Display omitted] • Carbon-matrix-embedded MS heterojunction of CoS 2 /NiS 2 is successfully prepared. • The as-prepared CoS 2 /NiS 2 @C exhibits exceptional sodium storage properties. • The mechanism is revealed by DFT calculations & i n/ex-situ characterizations. • The C-S bond promotes Na+ in the carbon matrix to migrate to embedded CoS 2 /NiS 2. • MS heterojunction in CoS 2 /NiS 2 accelerates electrochemical reaction kinetics. In this paper, carbon-matrix-embedded Mott–Schottky (MS) heterojunction of CoS 2 /NiS 2 (CoS 2 /NiS 2 @C) is prepared. The obtained CoS 2 /NiS 2 @C offers superior sodium storage performance such as large specific capacity (861.0 mAh/g at 2 A/g), extraordinary rate capability (649.2 mAh/g at 10 A/g, 371.4 mAh/g at 40 A/g) and excellent cycling stability (380.5 mAh/g after 3000 cycles at 10 A/g, and 298.5 mAh/g after 2000 cycles at 40 A/g). Electrochemical measurements and density functional theory (DFT) calculations as well as in/ex-situ characterization techniques are employed to reveal the underlying mechanisms. It is found that the outperforming sodium storage properties of CoS 2 /NiS 2 @C can be mainly attributed to the C-S bond and the MS heterojunction. The C-S bond formed at the interface between CoS 2 /NiS 2 and the carbon matrix promotes the migration of the sodium ions in the carbon matrix to the embedded CoS 2 /NiS 2 , while the MS heterojunction accelerates the electrochemical reaction kinetics of CoS 2 /NiS 2. Moreover, full-cell is assembled with CoS 2 /NiS 2 @C and Na 3 V 2 (PO 4) 3 /C to validate the practical application of CoS 2 /NiS 2 @C. The full-cell achieves both high specific capacity and outstanding rate performance, demonstrating the great application potential of such CoS 2 /NiS 2 @C anode in high-performance sodium-ion batteries. [ABSTRACT FROM AUTHOR]

A series of transition metals sulfides deposited on anatase titania (MS x /TiO 2) were prepared by precipitation of transition metals salts with thioacetamide in aqueous medium under reflux. The solids were characterized by XRD, XPS, temperature programmed reduction and transmission electron microscopy. The properties of as obtained catalysts were compared for the photocatalytic hydrogen evolution reaction (PHER) in pure methanol and water-isopropanol mixture. The sequences of PHER activity were compared with electrochemical HER and thiophene hydrodesulfurization (HDS) activity of the corresponding sulfides prepared by the same technique. For PHER, in both alcohols the most active photocatalysts contain hydrogenating sulfides of Co and Ru. However the PHER activity does not follow the same trend as electrocatalytic HER and thiophene HDS. Some sulfides, such as HgS or CuS, show poor activity in HDS and electrocatalytic HER, but have the PHER activity comparable with that of the best samples. This difference suggests that the PHER rate is not merely related to the hydrogen activating properties of the co-catalyst, but is enhanced by the transfer of photogenerated electrons from TiO 2 towards the sulfide. The ranking of the co-catalysts and the PHER activity depend also on the nature of the alcohol molecule, the overall PHER rates in water-isopropanol mixture being lower than in methanol. Image 1 • Seven transition metals sulfides MS x /TiO 2 prepared by the same method. • Photocatalytic HER activity is the best for RuS x , NiS 2 and CoS x in methanol and isopropanol. • Electrocatalytic HER activity ranking of MS x is different from the photocatalalytic one. • High dispersion of MS x sulfide on titania is a less important parameter. • Overall and relative photocatalytic HER activity depends on the organic molecule. [ABSTRACT FROM AUTHOR]

Graphical abstract Nickel sulfide (NiS) nanostructures with great crystallinity and high phase-purity were successfully synthesized using laser irradiation of an aqueous precursor solution under the ambient condition without further calcination. Given the remarkable value of electrochemically active surface area and synergistic effect of Ni3+ and Ni2+, the NiS synthesized for 4h delivered not only excellent electrocatalytic activities for hydrogen evolution reaction and but also high specific capacitance and remarkable rate capability for supercapacitors. Highlights • NiS nanoparticles was synthesized using laser irradiation of an aqueous precursor solution under the ambient condition. • Crystalline nanoparticles with high phase-purity were achieved without further calcination. • Other transition metal sulfides were also successfully obtained by this approach. • Efficient electrocatalytic HER activity and capacitive performances were achieved. Abstract Rational design and synthesis of transition metal sulfide complex nanostructures are significant for achieving desired materials properties for a variety of applications. Herein, we synthesized nickel sulfide (NiS) nanostructures using laser irradiation in an aqueous solution and under the ambient condition. Crystalline nanostructures with high phase-purity were achieved without further calcination. Other transition metal sulfides, such as CuS and ZnS, were also successfully synthesized using the laser irradiation approach, suggesting the practical application of this method. The hydrogen evolution reaction (HER) measurements show the NiS nanostructures synthesized for 4h (NiS-4h) not only exhibited competitive overpotential (−159 mV vs. RHE at 10 A/g), lower Tafel slope (218 mV/dec) but also delivered long-term stability (14 A/g at −250 mV vs. RHE for 12h). Moreover, the NiS-4h functioned as the electrode for supercapacitor with excellent specific capacitance (3761 F/g at 10 mV/s), reversibility and rate capability (1152 F/g at 100 mV/s). These superb electrochemical performances are attributed to the remarkable value of electrochemically active surface area (ECSA) and synergistic effect of Ni3+OOH for HER electrocatalytic activities, while the co-existence of Ni2+ and Ni3+ facilitates the rich redox reactions of NiS for supercapacitor. [ABSTRACT FROM AUTHOR]

Graphical abstract Herein, we proposed a facile strategy for the design of Au-MoS 2 nanoparticles with abundant edge sites and regular core-shell structure through the interface engineering. Highlights • Activating the pristine MoS 2 by introducing MoS 2 into core shell heterostructures through the interface engineering. • CNFs served as reactor and support to control the heterostructures of Au and MoS 2. • The Au-MoS 2 /CNFs exhibits the overpotential of 92 mV (10 mA cm−2) and a Tafel slope of 126 mV dec−1. Abstract Transition metal sulfides have been widely investigated and used as efficient catalysts for hydrogen evolution reactions (HER). However, the trade-off between catalytic activity and long-term stability represents a formidable challenge and has not been extensively addressed. Herein, we proposed a facile strategy for the design of Au-MoS 2 nanoparticles with abundant edge sites and regular core-shell structure through the interface engineering. The electrospun carbon nanofibers (CNFs) served as reactors and supports to control the preparation of core-shell heterostructures. Core-shell heterostructure exhibits more excellent catalytic than single component resulting from the synergistic effects at nano-interface. The obtained Au-MoS 2 /CNFs catalyst yield a current density of 10 mA cm−2 at the overpotential of 92 mV and a Tafel slope of 126 mV dec−1. Particularly, the durability of catalyst is relatively stable at the 50 h. The successful synthesis of core-shell nanocrystals provides a new path for designing advanced electrocatalysts. [ABSTRACT FROM AUTHOR]

Abstract Double-shelled hollow structures possess unique properties in energy conversion/storage fields due to their higher surface area, larger contact region with the electrolyte and much shortened paths of charge transfer. In this work, CoMoS x @Ni-CoMoS x hollow polyhedron catalyst with a double-shelled cage-in-cage structure is prepared by a sequence of template-engaged synthetic processes. In the synthetic procedure, (NH 4) 2 MoS 4 is applied as a multifunctional vulcanizator, which can conveniently afford Mo and S elements at the same time. Noteworthily, by comparing with single-shelled hollow CoMoS x and Ni-CoMoS x polyhedrons, the double-shelled CoMoS x @Ni-CoMoS x polyhedron catalyst demonstrates superior catalytic properties in the reduction of triiodide in dye-sensitized solar cells. The solar cell with CoMoS x @Ni-CoMoS x based counter electrode exhibits a high power conversion efficiency of 9.30%, which is much higher than that of Pt (8.01%). Graphical abstract Image 1 Highlights • Double-shelled CoMoS x @Ni-CoMoS x was synthesized by a template-engaged process. • (NH 4) 2 MoS 4 was used as a bifunctional vulcanizator to afford Mo and S elements. • CoMoS x @Ni-CoMoS x had large surface area and high catalytic activity. • The PCE of CoMoS x @Ni-CoMoS x (9.30%) was much higher than that of Pt (8.01%). [ABSTRACT FROM AUTHOR]

Highlights • A novel method (molten salt method followed by the hydrothermal process) was first introduced to synthesize SnS 2 @GO. • SnS 2 @GO with a regular hexagonal sheet-like nanostructure was obtained. • The SnS 2 @GO exhibited higher capacity and better cycling stability than that of pure SnS 2. Abstract Tin disulfide@graphene oxide (GO) nanocomposite was successfully synthesized using a novel method at the first time. SnO 2 quantum dots@GO (QDs@GO) prepared by traditional molten salt method was transformed into SnS 2 @GO nanocomposite in subsequent hydrothermal method. The as-synthesized SnS 2 @GO shows a regular hexagonal sheet-like nanostructure. Despite only a small amount of GO (2.4 wt%) is contained in the nanocomposite, it still exhibits high specific capacity, excellent rate capability and cycling performances as an anode material for lithium-ion batteries. This novel two-step method may provide an attractive alternative approach for the preparation of transition metal sulfides (TMSs) anode materials. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Cobalt sulfide nanosheets on stainless steel mesh (SSM/CoS) were successfully synthesized. • For the first time, SSM/CoS were used as sodium-ion battery anode. • The SSM/CoS anode show high capacity and rate performance. Abstract Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries (LIBs) in view of the natural abundance and low cost of sodium resource. Constructing high-performance anode is essential and challenging for the futuristic SIBs development. Transition metal sulfides have been proved as promising anode materials for SIBs due to their large specific capacities. Here, in situ assembly of cobalt sulfide nanosheets on stainless steel mesh (SSM/CoS) as a binder-free anode for SIBs is carried out through a facile electrochemical deposition procedure. The SSM/CoS products are directly used as anode electrodes without addition of binder and conductive additives. As a result, a high capacity of 313 mAh g−1 is obtained at a current density of 50 mA g−1 over 100 cycles. [ABSTRACT FROM AUTHOR]

Abstract Transition metal sulfides with hierarchical (ball in ball) micro/nanoporous structures have drawn wide spread interests for various applications, such as energy storage, catalysis, solar cells, owing to their unique features and intriguing properties. However, precise control of synthesizing process for hierarchical porous nanospheres of transition metal sulfides remains a big challenge. In addition, the charging and discharging process of transition metal sulfides in electrochemical storage is still a black box. Herein we design and precise control of synthesizing a transition metal sulfide with hierarchical porous nanosphere structure, namely cobalt sulfide hierarchical porous nanospheres (HPNs). Brownian snowball mechanism is put forward to explain the formation mechanism of CoS samples, which is supported by first-principles calculations. The proposed Brownian snowball mechanism helps us understand the formation process and facilitates comprehensive and precise manipulation, a key requirement for industrial scale-up. The CoS hierarchical porous nanospheres with a specific surface area of approximately 140 m2/g possess a total specific capacitance of 1310 F/g and 932 F/g at a current density of 5 A/g when used as electrode materials for electrochemical capacitors. The capacitance reflected hybrid electrical energy storage and is separated into double layer charging and the Faradaic contribution from the OH− ions reactions with surface atoms. It is demonstrated that Faradaic capacitance dominates in CoS hierarchical porous nanospheres exceeding 770 F/g by an analysis of the voltammetric sweep data. Graphical abstract Image 1 Highlights • Precise control of synthesizing process for cobalt sulfide hierarchical porous nanospheres. • Brownian snowball mechanism is put forward and supported by first-principles calculations. • The capacitance reflects hybrid electrical energy storage. • Largely improved EC performance could be attributed to the unique architecture. [ABSTRACT FROM AUTHOR]

Abstract Carbon-encapsulated transitional metal sulfides are considered as a promising anode material candidate for lithium ion batteries. Herein, a simple process is developed to synthesize 3D orostachys-like cobalt sulfides/C composites. This process is associated with the rational design of metal organic frameworks (MOFs) and subsequent in-situ sulfurization. Benefit from its unique structures, this novel 3D orostachys-like cobalt sulfides@C composites delivers an excellent charge capacity of 791 mAh g−1 after 100 cycles at 0.2 A g−1 as well as high stability of 667 mA g−1 after 700 cycles at 1 A g−1. Pseudocapacitive behaviors enhanced the electrochemical performance of 3D orostachys-like cobalt sulfides@C composites. Graphical abstract Scheme illustrating the benefit of hierarchical micro/nano-structure of Co 1-x S/C composites. Image 1 Highlights • Novel orostachys-like metal-organic frameworks were synthesized. • Cobalt sulfide nanoparticles uniformly embedded in hierarchical porous carbon network. • Several features of the hybrids lead to excellent lithium storage performance. • Pseudocapacitive behaviors enhanced the electrochemical performance of the hybrids. [ABSTRACT FROM AUTHOR]

Transition metal sulfides-based materials, as one type of promising oxygen reduction reaction (ORR) electrocatalysts have drawn increasing attention. Herein, we proposed a facile strategy to prepare iron-cobalt sulfides embedded in N,S-doped mesoporous carbon (Fe x Co 1-x S-T@NS-MC) via in situ polymerization and pyrolysis. Various characterization methods (e.g., Raman, BET, XPS, and electrochemical tests) are used to explore the differences between the microstructure and catalytic activity of these electrocatalysts. Notably, the sample Fe 0.5 Co 0.5 S-1000@NS-MC pyrolyzed at 1000 °C with an optimal iron/cobalt molar ratio (x = 0.5) exhibits the best ORR performance, which has the positive onset potential of 0.947 V vs. RHE, half-wave potential of 0.842 V vs. RHE and a large limiting current density of 5.63 mA cm −2 . Moreover, the results obtained from RRDE measurements indicate a four-electron process towards ORR for Fe 0.5 Co 0.5 S-1000@NS-MC catalyst. The combination and synergy of the controllable active centers (Fe-adjusted Co 9 S 8 /CoS with appropriate ratios) and hierarchical porous structures with large specific surface area render the outstanding ORR activity and electrochemical stability. Those results indicate that bimetallic sulfides-based materials are promising as ORR electrocatalysts. [ABSTRACT FROM AUTHOR]

Transition metal sulfide electrode materials have been widely studied in recent years, among which structural control is a terrific way to boost the electrochemical performance. Consequently, in this work, Mn-Ni-Co sulfide composites with a double-layer hollow cage structure were prepared by facile ion etching and hydrothermal vulcanization, and the inherent application value in the field of supercapacitors was verified. Due to the special double-layer hollow structure and the synergy between various metal elements, the prepared electrode material exhibited superior electrochemical performance: the specific capacity reached 2460 F g−1 at the current density of 1 A g−1 and maintained 81.1% even if the current was raised by 20 times. Then, Typha pollen-derived carbon was produced with salt (ZnCl 2 /FeCl 3) activation in one-step calcination. With a Mn-Ni-Co sulfide cathode and a Typha pollen-derived carbon anode, a hybrid supercapacitor device was assembled in a solution of 6 M KOH, which exhibited a great energy density of 80.4 Wh kg−1 at 800 W kg−1 and retained outstanding long-term cycling capability of 78.5% specific capacity after 10,000 cycles. The experimental results exhibit that the prepared composites have non-negligible application feasibility in supercapacitors. In addition, the simple structure control and tunable components make the method easily extended to the preparation of other materials, which has unique reference value for the preparation of multi-metal composites in other fields such as batteries and catalysis. [Display omitted] • The MNCS-2 with double-layer hollow structure and Typha pollen-derived carbon (TPC) was fabricated. • The MNCS-2 exhibits excellent rate performance. • The supercapacitor assembled by MNCS-2//TPC exhibits sufficient energy density. [ABSTRACT FROM AUTHOR]

• The unique chestnuts-like heterostructure was constructed via the carbonization and sulfidation of Ni-MOF. • Rational structure design and synergistic effect of different components and architectures co-boost capacitive behaviors. • The assembled asymmetric supercapacitor with outstanding cycling stability of 94.8% after 10,000 cycles at 1 A/g. Nickel sulfides are seemed as potential electrode materials of supercapacitors (SCs). Unfortunately, the unsatisfied structural stability of nickel sulfides lies in the way of their long-term working and applications. Herein, inspired by the biological structure of chestnuts, a ternary heterostructure composed of carbon nanotubes (CNTs) linked with NiS 2 @carbon microspheres (xNCC) was constructed by using Ni-MOF as precursor. Electrochemical evaluations showed that the as-obtained xNCC composites presented an optimal specific capacitance of 1572 F/g at 0.5 A/g. Additionally, the aqueous supercapacitor device exhibited a superior energy density of 21.6 Wh/kg, as well as a performance of 94.8% superior cycling stability after 10,000 cycles. It is supposed that the unique ternary heterostructure avoids/relieves the agglomeration of NiS 2 , weakens volume expansion and provides abundant as well as promote the stability of electrochemical active sites. More importantly, the 3D structural features of xNCC impart the electrodes with porous microstructures that are able to shorten the distance of ion-diffusion, thus enhancing the cycling stability and electrochemical performance. The present strategy may enlighten the structural design of electrode materials that can be further applied in SCs and other energy storage devices. [Display omitted] [ABSTRACT FROM AUTHOR]

• Using polydopamine as carbon source, N -doped carbon layer was obtained to make the structure more stable. • The combination of hollow structure and nanoflower structure alleviates the volume expansion problem. • The NiS 2 /FeS 2 @NC@NiFe LDH/FeO(OH) provides more active sites and increases the Li+ storage performance. As an anode material of lithium-ion batteries, transition metal sulfides have high theoretical capacity, and the structure design is an effective strategy to gain better electrochemical performance. Layered double hydroxides (LDHs) have significant preponderances in the field of energy storage on account of their exchangeable anions and biggish specific surface area. Nevertheless, its defects such as poor conductivity, easy agglomeration of nanosheets and biggish volume change during the cycle result in poor cycling durability and rate performance, which gravely constrain its further application. In this study, hollow yolk-shell NiS 2 /FeS 2 @NC@NiFe LDH/FeO(OH) nanoflower microspheres are prepared successfully by solvothermal and hydrothermal methods. Firstly, introducing N -doped carbon layer can availably heighten the electro-conductivity of the materials and stop the metallic particles from falling off to boost the structural stability. The design of hollow yolk-shell and nanoflower structure can effectively inhibit cubical expansion. In addition, the unique layered structure of the nanosheets can provide more active sites, shorten the ion transport path, and enhance the lithium storage performance. As a result, the NiS 2 /FeS 2 @NC@NiFe LDH/FeO(OH) electrode has splendid cycling performance (709.9 mAh g−1 at 0.2 A g−1 after 200 cycles). These prominent electrochemical properties demonstrate convincingly that the NiS 2 /FeS 2 @NC@NiFe LDH/FeO(OH) is a viable anode material. [ABSTRACT FROM AUTHOR]

In recent years, thanks to the excellent safety performance and extremely high theoretical specific capacity of rechargeable Al batteries, the development of Al battery cathode materials has become extremely competitive. In the structural design of cathode materials, the yolk-shell structure has a large amount of storage space and abundant active sites, giving full play to the advantages of synergy in building high-performance cathode structures. The construction of MoS 2 /NiS@S heterojunction interface effectively improves the conductivity of monometallic sulfide as cathode and improves the discharge performance of the electrode. The surface folds and pores of the heterojunction provide excellent channels for the free insertion and release of Al3+, reducing binding energy and enhancing Al3+ binding efficiency. It has maintained a reversible capacity of 130.19 mAh g−1 at 500 mA g−1 after 2000 cycles. This provides additional ideas for the development of transition metal sulfide materials in Al batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

Among transition metal sulfides, VS 4 is a promising candidate material for the positive electrode in rechargeable Li/metal-sulfide batteries, due to its long, flat plateau at about 2.0 V and its high theoretical capacity (1195 mAh g −1 ). In this study, we prepared VS 4 positive electrode material by heating in a sealed tube, and studied local structural changes during charge/discharge cycles via X-ray absorption and scattering spectroscopies, focusing on the reversibility of VS 4 . The findings reveal that a VS 4 -like local structure was formed in the first cycle, and that subsequent cycles showed reversible changes. [ABSTRACT FROM AUTHOR]

Transition-metal sulfides (TMDSs) stand out as promising Na-storage anodes due to their high theoretical capacities, low cost and non-toxic. However, the low realizable capacity and poor cycling performance severely hinder their large-scale applications. To achieve high reversible capacity with strong rate capability and long cycle life, N/S co-doped carbon coated NiS x (NiS x -NSC) was prepared via a facile and green calcination method, using thiourea as the nitrogen and sulfur sources. The as-prepared NiS x -NSC exhibits high reversible capacity of 338.4 mAh g −1 , outstanding rate capability of 201 mAh g −1 at 2 A g −1 and superior long-term cycling stability of 99.5% capacity retention over 300 cycles, suggesting one of the best Na-storage performances for nickel sulfide. First-principle calculations and EIS characterizations confirm that compared to the pure carbon coated NiS x , the N/S co-doping can modify the electronic structure of the composite to improve the high electronic and ionic transfer kinetics, leading to remarkable Na storage performances. [ABSTRACT FROM AUTHOR]

Precise deposition of cocatalysts on the outlet points of photo-generated electrons is helpful for highly efficient photocatalytic hydrogen evolution. Up to now, photochemical preparation of hydrogen production cocatalysts composed of earth-abundant elements is still great challenging and rarely reported. Herein, from the case of NiS/g-C 3 N 4 , a general photochemical synthesis route to typical transition metal sulfides as cocatalyst for hydrogen evolution was proposed. NiS were prepared by a facile and rapid photochemical method. The content of deposited NiS can be simply adjusted by the change of irradiation time. The optimized photocatalytic hydrogen evolution rate mounted up to 16 400 μmol g −1 h −1 with 0.76 wt% NiS loading, which is about 2500 times higher than that of pure g-C 3 N 4 . The photocatalytic H 2 evolution rate was stable after 40 h. The turnover number (TON) reached 1230 000 in 52 h with a turnover frequency (TOF) of 23 600 for NiS. Furthermore, the hydrogen evolution of the NiS/g-C 3 N 4 composite photocatalyst reached 28.3 mmol g −1 during 7 h under natural sunlight. The presence of NiS cocatalyst can efficiently promote the separation of photogenerated electron-hole pairs of g-C 3 N 4 , which was supported by the steady-state photoluminescence spectroscopy and photoelectro- chemical analyses. [ABSTRACT FROM AUTHOR]

Transition metal sulfides have attracted particular interests owing to their extremely higher specific capacity and more compatible with sulfide electrolyte than lithium transition-metal oxide for all-solid-state lithium batteries. FeS nanosheets with thickness of 10 nm are synthesized by a poly (vinyl alcohol)-assisted precipitation method and further successfully employed in Li/70%Li 2 S-29%P 2 S 5 –1%P 2 O 5 /Li 10 GeP 2 S 12 /FeS all-solid-state lithium batteries. The obtained all-solid-state lithium batteries show reversible discharge capacity of 550 mAh g − 1 after 50 cycles at current density of 0.1 A g − 1 and exhibit superior rate performances. [ABSTRACT FROM AUTHOR]

The Vulcan XC-72R modified WS 2 nanocomposite (WS 2 /C）was prepared by solid reaction process combined with sonication. The as-prepared WS 2 /C nanocomposite presents a laminated porous structure by SEM and TEM characterization. The electrochemical experiments show that the onset potential and the limiting-current density of WS 2 /C is 0.78 V and 4.99 mA cm −2 , respectively, which is much higher than, WS 2 (3.12 mA cm −2 ) and Vulcan XC-72R (2.79 mA cm −2 ). The number of transfer electrons in ORR at the WS 2 /C nanocomposite electrode is 3.70, which is close to four-electron process. Besides, the current density of WS 2 /C nanocomposites remained at 90% after 20,000 s, indicating its superior electrochemical stability. All these facts reveal that the as-prepared WS 2 /C nanocomposite can be regarded as a promising cathode ORR catalyst for fuel cell. [ABSTRACT FROM AUTHOR]

The present study focuses on anatase TiO 2 with various crystal facets, such as {101} and {001} combined with two-dimensional (2D) WS 2 nanolayers to form a heterojunction and the related photocatalytic activity. The {101} facets of anatase TiO 2 is superior in the compositing of WS 2 ; the composite shows a 90% enhancement compared with pristine TiO 2 than the composited WS 2 on the {001} facets which only boosted 7%. However, in our previous study, anatase TiO 2 with coexposed {101} and {001} facets demonstrated great improvement in photocatalytic activity in the composited MoS 2 . Results reveal that when anatase TiO 2 with coexposed {101} and {001} facets are composited with 2D transition metal sulfide (MoS 2 and WS 2 ), dual heterojunction will form. Some {101} facets are co-exposed with {001} facets, and this co-exposure will construct a crystal facet heterojunction. Moreover, a semiconductor heterojunction exists between TiO 2 and MoS 2 or WS 2 . This dual heterojunction is found to have a synergistic effect. It is revealed that the position of energy band plays a decision role in the dual heterojunction. This finding offers a deeper understanding in the construction of heterojunction on different crystal facets. [ABSTRACT FROM AUTHOR]

Transition metal sulfides as anodes for lithium-ion batteries (LIBs) have attracted much attention because of their large Li + storage capacity. However, the lower electrical conductivity and rapid capacity fading during the charge/discharge process strictly prohibit their practical applications. Here, a new strategy is adopted to accommodate the volume change and enhance the electrical conductivity by anchoring Co 1-x S and NiS nanocrystals on amorphous carbon coated multiwalled carbon nanotubes (CNTs). Benefiting from the unique structure, the Co 1-x S and NiS anodes present excellent electrochemical performances including remarkable cyclability and outstanding rate property. Furthermore, the electrochemical reaction process of the anodes is investigated by high-resolution transmission electron microscope and X-ray photoelectron spectroscopy technique. [ABSTRACT FROM AUTHOR]

Layered crystal structures are some of the most intensively studied intercalation hosts for guest ion insertion. For Mg insertion, layered transition metal sulfides or selenides have been used for reversible Mg intercalation; however, far less intercalation hosts have been found for layered oxides most likely because of the strong interaction between Mg 2+ and the oxide host. Here, we demonstrate that layered Li x Ni 0.5 Co 0.2 Mn 0.3 O 2 (NCM523), which is an important commercial electrode for Li-ion batteries but has been regarded as electrochemically inactive in rechargeable Mg batteries, can function as a reversible host for Mg 2+ if water opens up the layers and screens the electrostatic interaction between Mg 2+ and the host. Upon the formation of water-intercalated NCM523, the discharge capacity dramatically increases utilizing the multi-redox reaction of Ni 2+ /Ni 3+ /Ni 4+ , which exhibits an average voltage of ∼3.1 V ( vs. Mg/Mg 2+ ) in rechargeable Mg batteries with an energy density of 589 Wh kg −1 in the first discharge. [ABSTRACT FROM AUTHOR]

Transition metal chalcogenides are of interest for energy applications, including energy generation in photoelectrochemical cells and as electrodes for next-generation electrochemical energy storage. Synthetic routes for such chalcogenides typically involve extended heating at elevated temperatures for multiple weeks. We demonstrate here the feasibility of rapidly preparing select sulfide compounds in a matter of minutes, rather than weeks, using microwave-assisted heating in domestic microwaves. We report the preparations of phase pure FeS 2 , CoS 2 , and solid solutions thereof from the elements with only 40 min of heating. Conventional furnace and rapid microwave preparations of CuTi 2 S 4 both result in a majority of the targeted phase, even with the significantly shorter heating time of 40 min for microwave methods relative to 12 days using a conventional furnace. The preparations we describe for these compounds can be extended to related structures and chemistries and thus enable rapid screening of the properties and performance of various compositions of interest for electronic, optical, and electrochemical applications. [ABSTRACT FROM AUTHOR]

Newly three-dimensional graphene nanosheets/transition metal sulfide nanoparticles (i.e. 3-D GNs/Ni 3 S 2 NPs) composite was synthesized by an efficient quasi chemical vapor deposition (Q-CVD) technique in one-pot high temperature growth process. The as-prepared composite materials were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectric spectroscopy. The supercapacitive performances of electrodes were evaluated by cyclic voltammetry charging, discharging and electrochemical impedance spectroscopy. The 3-D GNs/Ni 3 S 2 NPs composite synthesized by the Q-CVD technique possesses favourable three-dimensional porous network of graphene and reasonable arrangement of Ni 3 S 2 NPs on the surface of graphene nanosheets. As a promising supercapacitor electrode, a relatively high specific capacitance of 652.5 F g −1 at current density of 1 A g −1 in 1 mol L −1 KOH aqueous solution, along with good cycling stability (with a 93% retention rate after 2000 cycles) were demonstrated for the 3-D GNs/Ni 3 S 2 NPs composite electrode. In addition, excellent electrochemical performances were also demonstrated for the asymmetric supercapacitor by using 3-D GNs/Ni 3 S 2 NPs as the cathode and 3-D GNs as the anode. [ABSTRACT FROM AUTHOR]

• Catalysts promoted the hydrogenolysis of resins and asphaltenes. • The bimetallic catalyst based on nickel and iron metals with the mass ratio of 1:1 exhibits the best catalytic performance. • Hydrothermal treatment of heavy oil in the presence of bimetallic nanoparticles significantly reduced its viscosity. • The destruction products of asphaltene fragments were observed by GC–MS in the composition of saturates and aromatics. • The content of asphaltenes decreases with the increase of iron metal concentration in the composition of the bimetallic catalyst. This paper examines the transformation of heavy oil composition in porous media of carbonate reservoir rocks under hydrothermal processes in the presence of transition metal sulfides, which form in-situ from the organic-soluble precursors. It was revealed that catalysts significantly promoted the destruction of asphaltenes. Its content was reduced from 15 wt.% to 12 wt.% in the presence of iron-based catalyst. The bimetallic catalyst based on nickel and iron with the mass ratio of 1:1 exhibited the best performance in terms of reducing heavy oil viscosity. Combination of two different metals allowed to involve the wide ranges of carbon-heteroatom bonds, which are mainly concentrated in resins and asphaltenes, into the hydrogenolysis reactions. Irreversible reduction of heavy oil viscosity in-place not only eases the further downstream processes such as pipeline transportation and refinery, but also decreases carbon footprints of the produced oil owing to the increase in the intensity of hydrogenation processes. [Display omitted] [ABSTRACT FROM AUTHOR]