Significantly enhanced ion-migration and sodium-storage capability derived by strongly coupled dual interfacial engineering in heterogeneous bimetallic sulfides with densified carbon matrix

The development of highly efficient sodium-ion batteries depends critically on the successful exploitation of advanced anode hosts that is capable of overcoming sluggish reaction kinetics while also withstanding severe structural deformation triggered by the large radius of Na^(+)-insertion.Herein,a hierarchically hybrid material with hetero-Co_(3)S_(4)/NiS hollow nanosphere packaged into a densified N-doped carbonmatrix(Co_(3)S_(4)/NiS@N-C)was designed and fabricated utilizing CoNi-glycerate as the self-sacrifice template,making the utmost of the synergistic effect of hetero-Co_(3)S_(4)/NiS with strong electric field and rich reaction active-sites together with the densified outer-carbon scaffolds with remarkable electronic conductivity and robust mechanical toughness.As anticipated,as-fabricated Co_(3)S_(4)/NiS@N-C anode affords remarkable specific capacity,prolonged cycle lifespan up to 2400 cycles with an only 0.05%fading each cycle at 20.0 A g^(−1),and excellent rate feature(354.9 mAh g^(−1)at 30.0 A g^(−1)),one of the best performances for most existing Co_(3)S_(4)/NiS-based anodes.Ex situ structural characterizations in tandem with theoretical analysis demonstrate the reversible insertion-conversion mechanism of initially proceeding with Na^(+)de-/intercalation and superior heterogeneous interfacial reaction behavior with strong Na^(+)-adsorption ability.Further,sodium-ion full cell and hybrid capacitor based on Co_(3)S_(4)/NiS@N-C anode exhibit impressive electrochemical characteristics on cycling performance and rate capability,showcasing its outstanding feasibility toward practical use.

Phosphorous-doped bimetallic sulfides embedded in heteroatom-doped carbon nanoarrays for flexible all-solid-state supercapacitors

Flexible supercapacitors(SCs)have become a popular research topic due to their extra-long service life,foldability,and wearability.Nevertheless,their low energy density restricts their applications.Here,we synthesized phosphorus-doped bimetallic sulfides embedded in heteroatom-doped(N,S,and P)carbon shells(P-ZCS/HC)using a simple approach to create high-performance flexible electrodes.The three-dimensional architecture made by interlaced nanosheets was preserved,and raised nanoparticles appeared on the rough surface during the annealing operation,increasing the specific surface area and potential exposure to the electrolyte.It is noteworthy that the optimal P-ZCS/HC electrode possessed a remarkable capacity of 1080 C g^(-1)at 1 A g^(-1)along with superb cycling stability.These extraordinary properties were primarily caused by plentiful redox reactions,enhanced conductivity,and synergic effects of the P-doped metal sulfides and heteroatom-doped carbon shells.Density functional theory simulations confirmed the good function of the P-doped electrodes and their ability to boost conductivity,improve reactive dynamics,and promote OH-adsorption.Notably,the assembled all-solid-state hybrid SC exhibited a maximum energy density of 62.9 W h kg^(-1)and a power density of 16 k W kg^(-1),while being able to maintain 92.0%of its initial capacity after 10,000 cycles.This systematic report provides new insight into the design and synthesis of electrodes with complex components and outstanding structures for the flexible energy field.

Influence of Metal Sulfides as Anode Catalysts on Performance of H_2S SOFC

Two anode catalysts with Pt, MoS2 and composite metal sulfides (MoS2+NiS), are investigated for electrochemical oxidation of hydrogen sulfide in solid oxide fuel cell (SOFC) at temperatures 750-850℃. The catalysts comprising MoS2 and MoSa+NiS exhibited good electrical conductivity and catalytic activity. MoS2 and composite catalysts were found to be more active than Pt, a widely used catalyst for high temperature H2S/O2 fuel cell at 750-850℃. However, MoS2 itself sublimes above 450℃. In contrast, composite catalysts containing both Mo and transition metal (Ni) are shown to be stable and effective in promoting the oxidation of H2S in SOFC up to 850℃. However, electric contact is poor between the platinum current collecting layer and the composite metal sulfide layer, so that the cell performance becomes worse. This problem is overcome by adding conductive Ag powder into the anode layer (forming MoS2+NiS+Ag anode material) to increase anode electrical conductance instead of applying a thin layer of platinum on the top of anode.

The application of nanostructured transition metal sulfides as anodes for lithium ion batteries

With wide application of electric vehicles and large-scale in energy storage systems, the requirement ofsecondary batteries with higher power density and better safety gets urgent. Owing to the merits of hightheoretical capacity, relatively low cost and suitable discharge voltage, much attention has been paid tothe transition metal sulfides. Recently, a large amount of research papers have reported about the appli-cation of transition metal sulfides in lithium ion batteries. However, the practical application of transitionmetal sulfides is still impeded by their fast capacity fading and poor rate performance. More well-focusedresearches should be operated towards the commercialization of transition metal sulfides in lithium ionbatteries. In this review, recent development of using transition metal sulfides such as copper sulfides,molybdenum sulfides, cobalt sulfides, and iron sulfides as electrode materials for lithium ion batteriesis presented. In addition, the electrochemical reaction mechanisms and synthetic strategy of transitionmetal sulfides are briefly summarized. The critical issues, challenges, and perspectives providing a fur-ther understanding of the associated electrochemical processes are also discussed.

Superhydrophobic Co/Fe sulfide nanoparticles and single-atoms doped carbon nanosheets composite air cathode for high-performance zinc-air batteries

Development of a high-performance bifunctional catalyst is essential for the actual implementation of zinc-air batteries in practical applications.Herein,a bifunctional cathode of Co_(3)S_(4)/FeS heterogeneous nanoparticles embedded in Co/Fe single-atom-loaded nitrogen-doped carbon nanosheets is designed.Cobalt-iron sulfides and single atomic sites with Co-N_(4)/Fe-N_(4)configurations are confirmed to coexist on the carbon matrix by EXAFS spectroscopy.3D self-supported super-hydrophobic multiphase composite cathode provides abundant active sites and facilitates gas–liquid-solid three-phase interface reactions,resulting in excellent electrocatalytic activity and batteries performance,i.e.,an OER overpotential(η_(10))of 260 mV,a half-wave potential(E_(1/2))of 0.872 V for ORR,aΔE of 0.618 V,and a discharge power density of 170 mW cm^(−2),a specific capacity of 816.3 mAh g^(−1).DFT analysis shows multiphase coupling of sulfide heterojunction through single-atomic metal doped carbon nanosheets reduces offset on center of electronic density of states before and after oxygen adsorption,and spin density of adsorbed oxygen with same spin orientation,leading to weakened charge/spin interactions between adsorbed oxygen and substrate,and a lowered oxygen adsorption energy to accelerate OER/ORR.

Manipulating d-d orbital hybridization induced by Mo-doped Co_(9)S_(8) nanorod arrays for high-efficiency water electrolysis

Precisely refining the electronic structure of electrocatalysts represents a powerful approach to further optimize the electrocatalytic performance.Herein,we demonstrate an ingenious d-d orbital hybridization concept to construct Mo-doped Co_(9)S_(8) nanorod arrays aligned on carbon cloth(CC)substrate(abbreviated as Mo-Co_(9)S_(8)@CC hereafter)as a high-efficiency bifunctional electrocatalyst toward water electrolysis.It has experimentally and theoretically validated that the 4d-3d orbital coupling between Mo dopant and Co site can effectively optimize the H_(2)O activation energy and lower H^(*)adsorption energy barrier,thereby leading to enhanced hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)activities.Thanks to the unique electronic and geometrical advantages,the optimized Mo-Co_(9)S_(8)@CC with appropriate Mo content exhibits outstanding bifunctional performance in alkaline solution,with the overpotentials of 75 and 234 mV for the delivery of a current density of 10 mA cm^(-2),small Tafel slopes of 53.8 and 39.9 mV dec~(-1)and long-term stabilities for at least 32 and 30 h for HER and OER,respectively.More impressively,a water splitting electrolylzer assembled by the self-supported Mo-Co_(9)S_(8)@CC electrode requires a low cell voltage of 1.53 V at 10 mA cm^(-2)and shows excellent stability and splendid reversibility,demonstrating a huge potential for affordable and scalable electrochemical H_(2) production.The innovational orbital hybridization strategy for electronic regulation herein provides an inspirable avenue for developing progressive electrocatalysts toward new energy systems.

Effect of pyrite, elemental sulfur and ferrous ions on EPS production by metal sulfide bioleaching microbes

Extracellular polymeric substances （EPS） produced by acidophilic bioleaching microorganisms play an important role in the production of acid mine drainage and metal sulfide bioleaching. EPS mediate the contact between microbial cells and growth substrates, having a pivotal role in organic film formation and bacterium-substratum interactions. The production and chemical composition of EPS produced by seven bioleaching strains grown with different substrates were studied. Analysis of the EPS extracted from these strains indicated that the EPS consisted of carbohydrates, proteins and galacturonic acid. The contents of EPS, carbohydrates, proteins and galacturonic acid of EPS were largely related to the kind of strain used and culture condition. The results show that EPS productions of microbes grown with pyrite were significantly higher than those of microbes grown with sulfur or FeSO4·7H2O. The highest EPS production of the seven acidiphilic strains was （159.43±3.93） mg/g, which was produced by Leptospirillum ferriphilum CBCBSUCSU208015 when cultivated with pyrite.

Interfacial engineering of graphitic carbon nitride(g-C_3N_4)-based metal sulfide heterojunction photocatalysts for energy conversion: A review

As one of the most appealing and attractive technologies, photocatalysis is widely used as a promising method to circumvent the environmental and energy problems. Due to its chemical stability and unique physicochemical, graphitic carbon nitride (g-C3N4) has become research hotspots in the community. However, g-C3N4 photocatalyst still suffers from many problems, resulting in unsatisfactory photocatalytic activity such as low specific surface area, high charge recombination and insufficient visible light utilization. Since 2009, g-C3N4-based heterostructures have attracted the attention of scientists worldwide for their greatly enhanced photocatalytic performance. Overall, this review summarizes the recent advances of g-C3N4-based nanocomposites modified with transition metal sulfide (TMS), including (1) preparation of pristine g-C3N4,(2) modification strategies of g-C3N4,(3) design principles of TMS-modified g-C3N4 heterostructured photocatalysts, and (4) applications in energy conversion. What is more, the characteristics and transfer mechanisms of each classification of the metal sulfide heterojunction system will be critically reviewed, spanning from the following categories:(1) Type I heterojunction,(2) Type II heterojunction,(3) p-n heterojunction,(4) Schottky junction and (5) Z-scheme heterojunction. Apart from that, the application of g-C3N4-based heterostructured photocatalysts in H2 evolution, CO2 reduction, N2 fixation and pollutant degradation will also be systematically presented. Last but not least, this review will conclude with invigorating perspectives, limitations and prospects for further advancing g-C3N4-based heterostructured photocatalysts toward practical benefits for a sustainable future.

Recent developments in metal phosphide and sulfide electrocatalysts for oxygen evolution reaction

Oxygen evolution reaction(OER),as an important half‐reaction involved in water splitting,has been intensely studied since the last century.Transition metal phosphide and sulfide‐based compounds have attracted increasing attention as active OER catalysts due to their excellent physical and chemical characters,and massive efforts have been devoted to improving the phosphide and sulfide‐based materials with better activity and stability in recent years.In this review,the recent progress on phosphide and sulfide‐based OER electrocatalysts in terms of chemical properties,synthetic methodologies,catalytic performances evaluation and improvement strategy is reviewed.The most accepted reaction pathways as well as the thermodynamics and electrochemistry of the OER are firstly introduced in brief,followed by a summary of the recent research and optimization strategy of phosphide and sulfide‐based OER electrocatalysts.Finally,some mechanistic studies of the active phase of phosphide and sulfide‐based compounds are discussed to give insight into the nature of active catalytic sites.It is expected to indicate guidance for further improving the performances of phosphide and sulfide‐based OER electrocatalysts.

Heavy Metals in a Sulfldic Minespoil: Fractions and Column Leaching

Fractions of various heavy metals in a sulfidic minespoil were investigated. Column leaching experimentwas also conducted to simulate 'acid mine drainage' (AMD) from the minespoil. The results show thatleaching of heavy metals from the minespoil was extremely significant during the initial water flushing.The amounts of heavy metals leached out dramatically reduced after leaching twice. It is worthwhile tonote that in this study, Zn, Mn, Fe, As and Ni in the first leachate exceeded the total amount of eachcorresponding water-extractable (1:5, soil:water) metal contained in the minespoil sample. This appears tosuggest that 1:5 water extraction did not allow accurate estimation of water-leachable concentrations of theabove heavy metals. This work has implications for the management of sulfidic minespoils. Acid drainageof great environmental concerns is likely to occur only during heavy rainfall events after substantial solubleand readily exchangeable acid and metals are accumulated in the minespoils. The slow-reacting fractionsother than water-soluble and readily exchangeable fractions may pose little environmental hazards. This isparticularly true for Pb, As and Ni.

Multi-Dimensional Composite Frame as Bifunctional Catalytic Medium for Ultra-Fast Charging Lithium-Sulfur Battery

The shuttle effect of soluble lithium polysulfides(LiPSs)between electrodes and slow reaction kinetics lead to extreme inefficiency and poor high current cycling stability,which limits the commercial application of Li-S batteries.Herein,the multi-dimensional composite frame has been proposed as the modified separator(MCCoS/PP)of Li-S battery,which is composed of CoS_(2) nanoparticles on alkali-treated MXene nanosheets and carbon nanotubes.Both experiments and theoretical calculations show that bifunctional catalytic activity can be achieved on the MCCoS/PP separator.It can not only promote the liquid-solid conversion in the reduction process,but also accelerate the decomposition of insoluble Li_(2)S in the oxidation process.In addition,LiPSs shuttle effect has been inhibited without a decrease in lithium-ion transference numbers.Simultaneously,the MCCoS/PP separator with good LiPSs adsorption capability arouses redistribution and fixing of active substances,which is also beneficial to the rate performance and cycling stability.The Li-S batteries with the MCCoS/PP separator have a specific capacity of 368.6 mAh g^(−1) at 20C,and the capacity decay per cycle is only 0.033%in 1000 cycles at 7C.Also,high area capacity(6.34 mAh cm^(−2))with a high sulfur loading(7.7 mg cm^(−2))and a low electrolyte/sulfur ratio(7.5μL mg^(−1))is achieved.

Interface enhanced well-dispersed Co9S8 nanocrystals as an efficient polysulfide host in lithium–sulfur batteries

The high specific capacity and energy density of lithium-sulfur batteries have attracted strong considerations on their fundamental mechanism and energy applications.However,polysulfide shuttle is still the key issue that impedes the development of Li-S batteries.Exploring nanocrystal hosts for polysulfide immobilization and conversion is a promising way.In this contribution,we have investigated well-dispersed Co9S8 nanocrystals grown on graphene oxide(GO)nanosheets with different degrees of dispersion as cathode host materials for Li-S batteries.The Co9S8-GO composite with 1 wt%GO(GCS1)has an average crystal size of 76 nm and shows the strongest adsorption capability toward lithium polysulfides.When used as the host material for the cathode of Li-S batteries,the GCS1-sulfur composite exhibits an initial specific capacity of^-1000 mAh g^-1 at 0.5 C and shows an average decay rate of 0.11%for 500 cycles.This work on the dispersion control of Co9S8 nanocrystals may inspire more investigations on well-dispersed nanocrystal based hosts for Li-S batteries.

Regulating the d band in WS_(2)@NC hierarchical nanospheres for efficient lithium polysulfide conversion in lithium-sulfur batteries

The performance of lithium-sulfur batteries is deteriorated by the inferior conductivity of sulfur,the shuttle effect of lithium polysulfides(LiPSs),sluggish redox kinetics of polysulfide intermediates and serious volumetric expansion of sulfur.To overcome these challenges,we report a versatile route to prepare multi-functional nanocomposites with tuable hierarchical structure via ammonium hydroxide(NH_(3)·H_(2) O)induced self-assembly.The versatility of the system has been demonstrated that the organization of the hierarchical structure can be regulated by adding different amounts of NH_(3)·H_(2) O,and WS_(2) and Co_(9)S_(8) with nitrogen-doped carbon coating(denoted as WS_(2)@NC and Co_(9)S_(8)@NC)can be prepared by adding different precursor salts.When the as-prepared materials are applied for Li-S batteries,the WS_(2)@NC composite exhibits a reversible capacity of 1107.4 mAh g^(-1) at 0.1 C after 500 cycles and even 728.9 mAh g^(-1) at2 C for 1000 cycles,which is significantly better than the Co_(9)S_(8) counterpart and other reported WS_(2) sulfur hosts.Experimentally,the advantageous performance of WS_(2) could be attributed to its higher surface area and total pore volume,giving rise to the easier access to electrolyte and better ability to buffer the volume change during the charge/discharge process.Theoretically,the density function theory(DFT)calculation reveals that the as-prepared WS_(2) has a higher binding energy towards LiPSs as well as a lower energy barrier for Li^(+)diffusion on the surface than Co_(9)S_(8).More significantly,the density of states(DOS)analysis further confirms that the superior performance is mainly ascribed to the more prominent shifting and the more charge compensation from d band of W than Co,which increase electronic concentration and give more hybridization of d-p orbitals in the Fermi level of the adsorbed Li2 S4 to accelerate the lithium polysulfide interfacial redox and conversion dynamics in WS_(2).By proposing this mechanism,this work sheds new light on the understanding of catalytic conversion of lithium polysulfides at the atomic level and the strategy to develop advanced cathode materials for high-performance lithium-sulfur batteries.

Advanced metal sulfide anode for potassium ion batteries

Potassium-ion batteries（KIBs） are a promising alternative to lithium-ion batteries owning to the abundance of potassium on Earth and the relatively low K/K＋redox couple. To date, KIBs remains its infancy and the investigation of anode materials mainly focused on carbon-based materials, which deliver limited reversible capacity. Hence, it is imperative to explore alternative anode materials with high reversible capacity for KIBs. Recently, a pioneering work from Chen’s group reported a nanocomposite of Sb2S3 nanoparticles anchored on porous S,N-codoped graphene（denoted as Sb2S3-SNG） as an advanced anode material for KIBs, which exhibited remarkable enhancements of both capacity and cycling stability, highlighting the rational structure design of Sb2S3-SNG for maximum utilization of Sb2S3 nanoparticles and graphene layers for energy storage applications in high-performance KIBs.

Fe/Co and Ni/Co-pentlandite type electrocatalysts for the hydrogen evolution reaction

Metal-rich transition metal sulfides recently gained increasing attention as electrocatalysts for the hydrogen evolution reaction(HER),as they are capable to overcome major challenges faced by sulfide-rich metal catalysts such as limited conductivity and the necessity of nanostructuring.Herein,we present the synthesis,characterization and electrocatalytic investigation of ternary metal-rich sulfide composites FexCo9-xS8 as well as Ni_(y)Co_(9-y)S_(8)(x=y=0-4.5),which possess pentlandite-type structures.In this study,we show a stepwise alteration of the binary cobalt pentlandite Co9S8 and report on the replacement of cobalt with up to 4.5 equivalents of either iron or nickel.These altered pentlandite composites facilitate the proton reduction in acidic media at different temperatures.We furthermore show that the stoichiometric variation has a decisive influence on the electrochemical activation/deactivation behavior of the catalysts under reductive electrocatalytic conditions.Here,Co-deficient composites display an improved HER performance in contrast to Co_(9)S_(8).Notably,Ni/Co compounds generally tend to show higher catalytic activities towards HER than their respective Fe/Co compounds.

Copper‐doped zinc sulfide nanoframes with three‐dimensional photocatalytic surfaces for enhanced solar driven H_(2) production

Solar‐to‐chemical energy conversion is perceived as one of the most potential solutions to the current energy and environmental crisis,yet requires major scientific endeavors on the development of efficient and sustainable photocatalysts.Remolding the composition and morphology of a semiconductor jointly for the purpose of improving photocatalysis efficiency remains challenging.Herein,we rationally fabricated Cu‐doped ZnS nanoframes via a simple conjunct strategy of substitutional doping,chemical acidic etching,and sulfidation,aiming at enhancing the light utilization and charge separation/transfer efficiency for solar‐light‐driven hydrogen generation.Cu‐doped zeolitic imidazolate framework‐8(ZIF‐8)rhombic dodecahedrons are transformed to hollow Cu‐ZIF‐8 nanoframes converted to Cu‐ZnS nanoframes with three‐dimensional photocatalytic active surfaces via anisotropic chemical etching,which is further converted to Cu‐ZnS nanoframes.By combining the merits of optimal heteroatom doping and frame‐like open architecture,the obtained 1%Cu‐doped ZnS nanoframe exhibits high photocatalytic activity under solar light irradiation with improved hydrogen production rate up to 8.30 mmol h^(–1) g^(–1) and excellent stability in the absence of cocatalysts,which is significantly improved in comparison with those of the bare ZnS and Cu‐ZnS with different morphologies.This work inspired by merging the merits of metal doping and anisotropic chemical etching may shed light on the rational design and fabrication of advanced photocatalysts.

“All‐In‐One” integrated ultrathin SnS2@3D multichannel carbon matrix power high‐areal–capacity lithium battery anode

Construction of a thickness‐independent electrode with high active material mass loading is crucial for the development of high energy rechargeable lithium battery.Herein,we fabricate an all‐in‐one integrated SnS2@3D multichannel carbon matrix(SnS2@3DMCM)electrode with in‐situ growth of ultrathin SnS2 nanosheets inside the inner walls of three dimensional(3D)multichannels.The interconnected conductive carbon matrix derived from natural wood acts as an integrated porous current collector to avail the electrons transport and accommodate massive SnS2 nanosheets,while plenty of 3D aligned multichannels facilitate fast ions transport with electrode thickness‐independent even under high mass loading.As expected,the integrated SnS2@3DMCM electrode exhibits remarkable electrochemical lithium storage performance,such as exceptional high‐areal‐capacity of 6.4 mAh cm−2,high rate capability of 3 mAh cm−2 under current of 6.8 mAcm−2(10 C),and stable cycling performance of 6.8 mAcm−2 with a high mass loading of 7mg cm−2.The 3D integrated porous electrode constructing conveniently with the natural source paves new avenues towards future high‐performance lithium batteries.

Electrolyte/Structure‑Dependent Cocktail Mediation Enabling High‑Rate/Low‑Plateau Metal Sulfide Anodes for Sodium Storage

As promising anodes for sodium-ion batteries,metal sulfides ubiquitously suffer from low-rate and high-plateau issues,greatly hindering their application in full-cells.Herein,exemplifying carbon nanotubes(CNTs)-stringed metal sulfides superstructure(CSC)assembled by nano-dispersed SnS_(2) and CoS_(2) phases,cocktail mediation effect similar to that of high-entropy materials is initially studied in ether-based electrolyte to solve the challenges.The high nano-dispersity of metal sulfides in CSC anode underlies the cocktail-like mediation effect,enabling the circumvention of intrinsic drawbacks of different metal sulfides.By utilizing ether-based electrolyte,the reversibility of metal sulfides is greatly improved,sustaining a long-life effectivity of cocktail-like mediation.As such,CSC effectively overcomes low-rate flaw of SnS_(2) and highplateau demerit of CoS_(2),simultaneously realizes a high rate and a low plateau.In half-cells,CSC delivers an ultrahigh-rate capability of 327.6 mAh g^(−1) anode at 20 A g^(−1),far outperforming those of monometallic sulfides(SnS_(2),CoS_(2))and their mixtures.Compared with CoS_(2) phase and SnS_(2)/CoS_(2) mixture,CSC shows remarkably lowered average charge voltage up to ca.0.62 V.As-assembled CSC//Na1.5VPO4.8F0.7 full-cell shows a good rate capability(0.05~1.0 A g^(−1),120.3 mAh g^(−1) electrode at 0.05 A g^(−1))and a high average discharge voltage up to 2.57 V,comparable to full-cells with alloy-type anodes.Kinetics analysis verifies that the cocktail-like mediation effect largely boosts the charge transfer and ionic diffusion in CSC,compared with single phase and mixed phases.Further mechanism study reveals that alternative and complementary electrochemical processes between nano-dispersed SnS_(2) and CoS_(2) phases are responsible for the lowered charge voltage of CSC.This electrolyte/structure-dependent cocktail-like mediation effect effectively enhances the practicability of metal sulfide anodes,which will boost the development of high-rate/-voltage sodium-ion full batteries.

Single-phase bimetal sulfide or metal sulfide heterojunction:Which one is better for reversible oxygen electrocatalyst?

Bimetallic sulfides,integrating the merits of individual components,are ideal structures for efficient electrocatalysis.However,for bimetallic sulfides including metal sulfide heterojunctions(MSH)and singlephase bimetallic sulfides(SBS),it is still unclear about which one has better catalytic activity toward reversible oxygen catalysis and its difference on catalytic mechanism.In this work,we demonstrate a bimetallic sulfide electrocatalyst that could transform from metal sulfide heterojunction(CoS/FeS)to single-phase bimetallic sulfide(CoFeS_(2))through a facile temperature control strategy.The single-phase bimetallic sulfide(CoFeS_(2))affords high intrinsic activity,fast reaction kinetics and superior durability toward oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).Density functional theory(DFT)simulations reveal that the(CoFeS_(2))has homogeneous electron distribution of the CoFeS_(2)structure,improves the central energy level of d band,and optimizes the O*and OOH*intermediate and efficiently reduces the energy barrier of the reaction rate-determining step(RDS).The assembled rechargeable zincair battery is more stable than the Pt/C and IrO_(2) assemblies due to the excellent electrocatalytic activity and stability of CoFeS_(2)/NC,suggesting that it has potential for use in practical applications.

ZIF-67 derived CoSx/NC catalysts for selective reduction of nitro compounds

Transition metal sulfides(TMSs)-based materials have been extensively investigated as effective non-noble catalysts for various applications.However,the exploration of TMSs-based catalysts for hydrogenation of nitro compounds is limited.Herein,CoSx/NC catalysts were prepared by solvothermal sulfurization of ZIF-67,followed by high-temperature annealing(300–600℃)under NH3 atmosphere.It was found that the structures and compositions of the as-prepared CoSx/NC can be readily tuned by varying the annealing temperature.Particularly,CoSx/NC-500,which possesses higher degree of S defects and larger specific surface areas,can achieve high conversion,selectivity and stability for catalytic reduction of nitro compounds into amines under mild reaction conditions.