Highly uniform Co-Cu bimetallic sulfides for rechargeable alkaline aqueous zinc batteries

Rechargeable alkaline aqueous zinc batteries(RAZBs)have attracted increasing attention.However,most RAZBs are hindered by the limited availability of cathode materials.The practical electrochemical performance of most cathode materials is lower than the theoretical value due to their poor electrical conductivity and low utilization capacity.In this work,we develop a facile hydrothermal procedure to prepare highly uniform bimetallic sulfides as novel cathode materials for RAZBs.Copper-cobalt binary metallic oxides materials possess higher conductivity and larger capacity compared with their mono-metal oxides compounds due to bimetallic synergistic effects and multiple oxidation states.Furthermore,bimetallic sulfide compounds have smaller bond energy and longer bond length than their oxides,leading to less structural damage,faster kinetics of electrochemical reactions,and better stability.The as-prepared Co-Cu bimetallic sulfides show enhanced electrochemical performance due to various valences of Co and Cu as well as the existence of S.As a result,aqueous Zn/CuCo_(2)S_(4) battery shows a high specific capacity of 117.4 mAh/g at 4 A/g and a good cycle life of over 8000 cycles.Based on PANa hydrogel electrolytes,a flexible Zn/CuCo_(2)S_(4) battery demonstrates excellent cycling stability.This battery can also meet the requirements of electronic devices with different shapes and performs well in extreme environments,such as freezing,drilling,and hammering.This work opens new avenues to obtain high-rate and long-life cathode materials for RAZBs by utilizing the synergistic effects of bimetallic sulfides and provides a new platform for flexible energy storage devices.

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.

Controllable fabrication of FeCoS_(4) nanoparticles/S-doped bowl-shaped hollow carbon as efficient lithium storage anode

To address the low conductivity and easy agglomeration of transition metal sulfide nanoparticles,FeCoS_(4) nanoparticles embedded in S-doped hollow carbon(FeCoS_(4)@S-HC)composites were successfully fabricated through a combination of hydrothermal processes and sulfidation treatment.The unique bowlshaped FeCoS_(4)/S-HC composites exhibit excellent structural stability with a high specific surface area of 303.7 m^(2)·g^(-1) and a pore volume of 0.93 cm^(3)·g^(-1).When applied as anode material for lithium-ion batteries,the FeCoS_(4)@S-HC anode exhibits efficient lithium storage with high reversible specific capacity(970.2 mA·h·g^(-1) at 100 mA·g^(-1))and enhanced cycling stability(574 mA·h·g^(-1) at 0.2 A·g^(-1) after 350 cycles,a capacity retention of 84%).The excellent lithium storage is attributed to the fact that the bimetallic FeCoS_(4) nanoparticles with abundant active sites can accelerate the electrochemical reaction kinetics,and the bowl-shaped S-HC structure can provide a stable mechanical structure to suppress volume expansion.

Bifunctional oxygen electrode cobalt–nickel sulfides catalysts originated from intercalated LDH precursors

Bimetallic cobalt-nickel sulfide nanoparticles anchored on S-,N-codoped holey carbon nanosheets(CoNiS-T@NCFs)with a hydrangea-like morphology,were synthesized via a confinement synthesis route,in which an intercalated LDH precursor was subjected to the interlayer-confined carbonization and host-layer sulfurization.The phase transformation and structure evolution(e.g.,atom site occupancy,crystallite size,and cell volume)of the CoNi-S-T@NCFs electrocatalysts,as a function of sulfurization temperatures,were confirmed by X-ray diffraction and Rietveld analyses.The sulfur vacancies effectively enhance the electrocatalytic activity,while the synergistic effect of(Co,Ni)7 S8 alloy and S,N-codoped carbon matrix facilitates the electron transfer and accelerates reaction kinetics,making CoNi-S-900@NCFs an efficient and stable bifunctional electrocatalyst for oxygen reduction reaction(ORR).The rich highvalence Co(Ⅲ)and Ni(Ⅲ)of CoNi-S-900@NCFs facilitates the in-situ transformation of the metal(oxy)hydroxides intermediates with high catalytic activity for oxygen evolution reaction(OER).Thus,with a bifunctional parameter,ΔE,of 0.75 V(E_(j=10,OER)-E_(1/2,ORR)),this electrocatalyst slightly outperforms the state-of-the-art commercial Pt/C+RuO_(2)/C catalyst(ΔE=0.76 V)in alkaline medium.This work demonstrates the influence that the sulfurization temperature has on the relationship between the structure and electrocatalytic performance of bimetallic sulfides prepared by the synthesis strategy using the intercalated LDH precursor.This strategy can be extended to prepare other chalcogenides with binary or ternary transition metals.

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

Herein,a facile synthetic strategy is proposed to fabricate high-performance electrocatalysts for rechargeable Zn-air batteries(ZABs).Heterostructured NiCo/NiCo_(2)S_(4) nanoparticles encapsulated in N-,S-co-doped CNT(NiCo/NiCo_(2)S_(4)@NSCNT) are synthesized via co-precipitation,thermal carbonization,and partial sulfidation processes.The strongly coupled NiCo/NiCo_(2)S_(4) heterostructure can improve the redox property and charge transfer ability.Also,the CNTs with abundant foreign dopants provide high electrical conductivity and abundant defect sites for both the oxygen evolution reaction(OER) and oxygen reduction reaction(ORR).The prepared NiCo/NiCo_(2)S_(4)@NSCNT electrocatalyst exhibits a low overpotential of 349 mV at a current density of 10 mA cm-2 and a half-wave potential of 0.865 V for the OER and ORR,respectively.Moreover,the ZAB assembled using as-prepared NiCo/NiCo_(2)S_(4)@NSCNT can provide superior specific capacity(756.16 mA h g_(Zn)^(-1)],peak power density(155.82 mW cm^(-2)),and long-term cyclability compared to those of the precious metal-based electrocatalyst(Pt/C+RuO_(2)).

Open and close-ended CoMoS_(3) nanotubes for hydrogen evolution in acidic and basic conditions

Electrochemical hydrogen evolution reaction(HER) is a promising route to harvest high-purity hydrogen(H_(2)).Efficient and selective energy transformations rely on the development of novel catalytic materials in terms of compositions and structures that survive under harsh conditions.This study focuses on a unique nanostructured CoMoS_(3) catalyst for HER under strong acidic and basic electrolyte.The morphologies of the catalysts are fine-tuned by altering reaction times in a hydrothermal reaction.Limited reaction time generates twisted thin-sheet CoMoS_(3)(12 h),which spins into a nanotube with an extended synthetic time(16 h).As the reaction time increases to 20 h,the CoMoS_(3) composite creates open-ended nanotubes,facilitating reactants to penetrate and react actively in the inner space of the nanotubes.Further,prolonged reaction time(24 h) results in the formation of the close-ended CoMoS_(3) nanotubes.We find out that the open-ended structure plays an important role in achieving fast kinetics as well as creating more active sites in HER reaction.The catalyst delivers a profound performance under both acidic and basic conditions,with overpotentials of 93 mV and 115 mV(at a current density of 10 mA/cm^(2)) in the acidic and basic electrolytes,respectively.Moreover,it shows superior long-term durability in both solutions.This work will provide a great foundation for understanding the morphology effect with the same composited catalyst towards energy conversion reactions,not limited to HER.

Oil-soluble Ni-Mo sulfide nanoparticles and their hydrogenation catalytic properties

Oil-soluble bimetallic Ni-Mo sulfide nanoparticles（NiMoS） with narrow size distribution were successfully synthesized through a composite-surfactants-assisted-solvothermal process.The surface functionality and lipophilicity of the Ni-Mo sulfides were shown by transmission electronic microscopy,Fourier transform infrared and ultraviolet spectroscopy.The as-prepared Ni-Mo sulfides supported on activated carbon（NiMoS/AC） exhibited enhanced catalytic activity towards naphthalene hydrogenation instead of cracking.For comparison,CoMoS/AC and MoS2/AC catalysts were also prepared through similar procedures,and it was found that their catalytic performance decreased in the order of NiMoS/AC〉CoMoS/AC〉MoS2/AC.Furthermore,the activity of the bimetallic NiMoS nanocatalyst can be effectively tuned via variation of the atomic ratio of Ni/（Ni＋Mo）.

Effective removal of chlorinated organic pollutants by bimetallic iron-nickel sulfide activation of peroxydisulfate

Chlorinated organic pollutants(COPs)have caused serious contaminants in soil and groundwater,hence developing methods to remove these pollutants is necessary and urgent.By a simple hydrothermal method,we synthesized the bimetallic iron-nickel sulfide(FeNiS)particles which exhibited excellent catalytic property of COPs removal.FeNiS was chosen as the peroxydisulfate(PDS)activator to removal COPs including 4-chlorophenol(4-CP),1,4-dichlorophenol(1,4-DCP)and 2,4,6-trichlorophenol(2,4,6-TCP).The results show that FeNiS can efficiently activate PDS to produce sulfate radical(SO4·-)which plays major role in the oxidative dechlorination and degradation due to its strong oxidizing property and the ability of producing hydroxyl radicals(·OH)in the alkaline condition.Meanwhile,the Cl-abscised from COPs during the dechlorination can turn into the chlorine radicals and enhance the degradation and cause further mineralization of intermediate products.This bimetallic FeNiS catalyst is a promising PDS activator for removal of chlorinated organics.

Bimetallic Sulfide/Sulfur Doped T3C2TA:MXene Nanocomposites as High-performance Anode Materials for Sodium-ion Batteries

The application of transition metal dichalcogenides(TMDs)as anode materials in sodium-ion batteries(SIBs) has been hindered by low conductivity and poor cyclability.Herein,we report the synthesis of CoxFe1-xS2 bimetallic sulfide/sulfur-doped Ti3C2 MXene nanocomposites(CoxFe1-xS2@S-Ti3C2)by a facile co-precipitation process and thermal-sulfurization reaction.The interconnected 3D frameworks consisting of MXene nanosheets can effectively buffer the volume change and enhance the charge transfer.In particular,sulfur-doped MXene nanosheets provide rich active sites for sodium storage and restrain sulfur loss during charging/discharging processes,leading the increase of specific capacity and cycling the stability of anode materials.As a result,CoxFe1-xS2@S-Ti3C2 anodes exhibited high capacity,high rate capability and long cycle life(399mA·h/g at 5A/g with an 94% capacity retention after 600 cycles).

Heterostructured NiS_(2)@SnS_(2) hollow spheres as superior high-rate and durable anodes for sodium-ion batteries

Tin-based sulfides have attracted increasing attention as anodes for sodium-ion batteries(SIBs) owing to their high theoretical capacity;however, the poor rate capability and inferior cycling stability caused by the low electrical conductivity, sluggish kinetics and drastic volume variations during cycling have greatly hampered their practical applications. Herein, heterostructured NiS_(2)@SnS_(2) hybrid spheres were delicately designed and constructed by anchoring interconnected SnS_(2) nanosheets on metalorganic frameworks(MOFs)-derived Ni S_(2) hollow spheres coupled with N-doped carbon skeleton through facile solvothermal and sulfurization/carbonization processes. The unique hollow heterostructure with highly conductive carbon matrix can effectively facilitate the charge transfer kinetics and ensure the desired buffer space while endowing more active sites and enhanced structural integrity, as demonstrated by the experimental and density functional theory(DFT) results. Benefitting from these merits, the NiS_(2)@SnS_(2) hybrid composite displays a high reversible capacity of 820 m Ah g^(-1) after 250 cycles at 1 A g^(-1), and retains a value of 673 m Ah g^(-1)after 1,300 cycles at 5 A g^(-1), manifesting the excellent high-rate and durable sodium storage behaviors when applied in SIBs. This study shall shed more light on the fabricating and interface engineering of other transition metal-based composite anodes for high-performance SIBs.