KOH-assisted aqueous synthesis of bimetallic metal-organic frameworks and their derived selenide composites for efficient lithium storage

To solve low efficiency,environmental pollution,and toxicity for synthesizing zeolitic imidazolate frameworks(ZIFs)in organic solvents,a KOH-assisted aqueous strategy is proposed to synthesize bimetallic ZIFs polyhedrons,which are used as precursors to prepare bimetallic selenide and N-doped carbon(NC)composites.Among them,Fe–Co–Se/NC retains the three-dimensional(3D)polyhedrons with mesoporous structure,and Fe–Co–Se nanoparticles are uniform in size and evenly distributed.When assessed as anode material for lithium-ion batteries,Fe–Co–Se/NC achieves an excellent initial specific capacity of 1165.9 m Ah·g^(-1)at 1.0 A·g^(-1),and the reversible capacity of Fe–Co–Se/NC anode is 1247.4 m Ah·g^(-1)after 550 cycles.It is attributed to that the uniform composite of bimetallic selenides and N-doped carbon can effectively tune redox active sites,the stable 3D structure of Fe–Co–Se/NCs guarantees the structural stability and wettability of the electrolyte,and the uniform distribution of Fe–Co–S nanoparticles in size esuppresses the volume expansion and accelerates the electrochemical reaction kinetics.

Ultralong nitrogen/sulfur Co-doped carbon nano-hollowsphere chains with encapsulated cobalt nanoparticles for highly efficient oxygen electrocatalysis

The development of simple and effective strategies to prepare electrocatalysts,which possess unique and stable structures comprised of metal/nonmetallic atoms for oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),is currently an urgent issue.Herein,an efficient bifunctional electrocatalyst featured by ultralong N,S-doped carbon nano-hollow-sphere chains about 1300 nm with encapsulated Co nanoparticles(Co-CNHSCs)is developed.The multifunctional catalytic properties of Co together with the heteroatom-induced charge redistribution(i.e.,modulating the electronic structure of the active site)result in superior catalytic activities toward OER and ORR in alkaline media.The optimized catalyst Co-CNHSC-3 displays an outstanding electrocatalytic ability for ORR and OER,a high specific capacity of 1023.6 mAh gZn^(-1),and excellent reversibility after 80 h at 10mA cm^(-2)in a Zn-air battery system.This work presents a new strategy for the design and synthesis of efficient multifunctional carbon-based catalysts for energy storage and conversion devices.

KOH-assisted aqueous synthesis of ZIF-67 with high-yield and its derived cobalt selenide/carbon composites for high-performance Li-ion batteries

To solve the environmental pollution and low yield during the sythesis of zeolitic imidazolate frameworks(ZIFs)and their derived materials,a KOH-assisted aqueous strategy is proposed to synthesize cobalt zeolitic imidazolate framework(ZIF-67)polyhedrons,which are used as precursors to prepare cobalt selenide/carbon composites with different crystal phases(Co_(0.85)Se,CoSe_2).When evaluated as anode material for lithium ion batteries,Co_(0.85)Se/C composites deliver a reversible capacity of 758.7 m A·h·g^(-1)with a capacity retention rate of 90.5%at 1.0 A·g^(-1)after 500 cycles,and the superior rate capability is 620 m A·h·g^(-1)at 2.0 A·g^(-1).The addition of KOH accelerates the production of ZIF-67 crystals by boosting deprotonation of dimethylimidazole,resulting in rapid growth and structures transition from two-dimensional to three-dimensional of ZIF-67 in aqueous solution,which greatly promotes the application of MOFs in the field of energy storage and conversion.

绿色船舶引领‘Chem+’复合型创新人才培养的探索与实践

江苏科技大学面向海洋强国战略和船舶绿色发展需求,构建了以化学为核心的‘Chem+’学科专业群,以立德树人为根本,以培养绿色船舶领域迫切需要的复合型创新人才为目标,通过学科交叉、多元协同、船魂引领,重构‘Chem+’人才培养体系,开设"走向深蓝"系列金课,着重培养学生的绿色理念、创新能力和行业素养,实现知识传授、能力培养、价值塑造深度融合,形成鲜明的船舶与海洋办学特色。‘Chem+’学科专业建设和复合型创新人才培养成效显著,形成了系列化经验,相关成果对应用化学专业特色建设和新工科改造发挥了示范和引领作用。

Fabricating titanium dioxide/N-doped carbon nanofibers as advanced interlayer for improving cycling reversibility of lithium-sulfur batteries

"Shuttle effect" is detrimental for maintaining the high capacity and cycling reversibility of lithium-sulfur batteries(LSBs).To inhibit polysulfide migration,N-doped carbon nanofibers(N-CNFs) membrane comprising TiO_(2)nanoparticles(TiO_(2)/N-CNFs) is fabricated using an electrospinning-calcination method and further applied as interlayer in LSBs.The TiO_(2)/N-CNFs interlayer helps the battery to deliver a high specific capacity of 1155.2 mA·h·g^(-1)at 0.2 C with high Coulombic efficiency,good rate capability and stability.When cycling at 0.5 C,a capacity retention rate of 62.4% is achieved over 300 cycles,which is higher than that of CNFs and TiO_(2)/CNFs counterparts.The excellent performance should mainly be attributed to the alleviated "shuttle effect" deriving from high polysulfide trapping ability of TiO_(2)nanoparticles and N heteroatoms in interwoven CNFs.

Cobalt-based multicomponent nanoparticles supported on N-doped graphene as advanced cathodic catalyst for zinc-air batteries

To improve the efficiency of cathodic oxygen reduction reaction(ORR)in zinc-air batteries(ZABs),an adsorption-complexation-calcination method was proposed to generate cobalt-based multicomponent nanoparticles comprising Co,Co_(3)O_(4)and CoN,as well as numerous N heteroatoms,on graphene nanosheets(Co/Co_(3)O_(4)/CoN/NG).The Co/Co_(3)O_(4)/CoN nanoparticles with the size of less than 50 nm are homogeneously dispersed on N-doped graphene(NG)substrate,which greatly improve the catalytic behaviors for ORR.The results show that the half-wave potential is as high as 0.80 V vs.RHE and the limiting current density is 4.60 mA·cm^(−2),which are close to those of commercially available platinum/carbon(Pt/C)catalysts.Applying as cathodic catalyst for ZABs,the battery shows large specific capacity and open circuit voltage of 843.0 mAh∙g^(−1) and 1.41 V,respectively.The excellent performance is attributed to the efficient two-dimensional structure with high accessible surface area and the numerous multiple active sites provided by highly scattered Co/Co_(3)O_(4)/CoN particles and doped nitrogen on the carbon matrix.

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.

High N-doped hierarchical porous carbon networks with expanded interlayers for efficient sodium storage

Sodium-ion batteries (SIBs) have been attracting considerable attention as a promising candidate for large-scale energy storage because of the abundance and low-cost of sodium resources. However, lack of appropriate anode materials impedes further applications. Herein, a novel self-template strategy is designed to synthesize uniform flowerlike N-doped hierarchical porous carbon networks (NHPCN) with high content of N (15.31 at.%) assembled by ultrathin nanosheets via a self-synthesized single precursor and subsequent thermal annealing. Relying on the synergetic coordination of benzimidazole and 2-methylimidazole with metal ions to produce a flowerlike network, a self-formed single precursor can be harvested. Due to the structural and compositional advantages, including the high N doping, the expanded interlayer spacing, the ultrathin two-dimensional nano-sized subunits, and the three-dimensional porous network structure, these unique NHPCN flowers deliver ultrahigh reversible capacities of 453.7 mAh·g^−1 at 0.1 A·g^−1 and 242.5 mAh·g^−1 at 1 A·g^−1 for 2,500 cycles with exceptional rate capability of 5 A·g^−1 with reversible capacities of 201.2 mAh·g^−1. The greatly improved sodium storage performance of NHPCN confirms the importance of reasonable engineering and synthesis of hierarchical carbon with unique structures.

Zephyranthes-like Co2NiSe4 arrays grown on 3D porous carbon frame-work as electrodes for advanced supercapacitors and sodium-ion batteries

Developing suitable electrode materials for electrochemical energy storage devices by biomorph assisted design has become a fascinating topic due to the fantastic properties derived from bio-architectures.Herein,zephyranthes-like Co_(2)NiSe_(4)arrays grown on butterfly wings derived three-dimensional(3D)carbon framework(Z-Co_(2)NiSe_(4)/BWC)is fabricated via hydrothermal assembly and further conversion method.Benefiting from its unique structure and multi-components,the obtained Z-Co_(2)NiSe_(4)/BWC electrode for supercapacitor delivers an excellent specific capacitance of 2,280 F·g^(-1)at 1 A·g^(-1).Impressively,the constructed asymmetric supercapacitor using Co_(2)NiSe_(4)/BWC as positive electrode and activated butterfly wings carbon as negative electrode acquires a high energy density of 42.9 Wh·kg^(-1)at a power density of 800 W·kg^(-1)with robust stability of 94.6%capacitance retention at 10 A·g^(-1)after 5,000 cycles.Moreover,the Z-Co_(2)NiSe_(4)/BWC as anode for sodium-ion batteries exhibits a high specific capacity of 568 mAh·g^(-1)at 0.1 A·g^(-1)and high cycling stability(maintaining 80.1%of the second cycle after 100 cycles).The outstanding electrochemical performances are ascribed to that the synergistic effect of bimetallic selenides and N-doped carbon improves electrochemical activities and conductivity.One-dimensional(1D)nanoneedles grown on 3D porous framework increase the exposure of redox-active sites,endow adequate transmission channels of electrons/ions,and guarantee stability of the electrode during charge/discharge processes.This study will shed light on the avenue towards extending such nanohybrids to excellent energy storage applications.

A channel-confined strategy for synthesizing CoN-CoO_(x)/C as efficient oxygen reduction electrocatalyst for advanced zinc-air batteries

Designing hybrid transition metal compounds with optimized electronic structure and firmly dispersing them on a matrix to avoid aggregation and shedding is of great significance for achieving high electrocatalytic performances.Herein,an adsorption-complexation-calcination strategy based on channel confining effect is explored to obtain CoN-CoO_(x)hybrid nanoparticles uniformly dispersed in mesoporous carbon.The CoN-CoO_(x)/C composite exhibits excellent electrocatalytic behavior for oxygen reduction reaction(ORR).The half-wave potential and durability are comparable or superior to those of Pt/C.When applying as cathode catalyst for a primary zinc-air battery,the open-circuit voltage and peak power density reach up to 1.394 V and 109.8 mW·cm^(−2),respectively.A high gravimetric energy density of 950.3 Wh·kgZn^(−1) is delivered at 10 mA·cm^(−2) with good rate capability and stability.Density functional theory(DFT)calculation demonstrates the favorable ORR intermediate adsorbability and metallic characteristics of CoN grains with oxide hybridization to optimize the electronic structure.This work provides a facile adjustable approach for obtaining highly dispersed nanoparticles with controllable hybrid composition on a substrate,which is important for future design and optimization of high-performance electrocatalysts.

Preparation and lithium storage performances of g-C_(3)N_(4)/Si nanocomposites as anode materials for lithium-ion battery

As the anode material of lithium-ion battery,silicon-based materials have a high theoretical capacity,but their volume changes greatly in the charging and discharging process.To ameliorate the volume expansion issue of silicobased anode materials,g-C_(3)N_(4)/Si nanocomposites are prepared by using the magnesium thermal reduction technique.It is well known that g-C_(3)N_(4)/Si nanocomposites can not only improve the electronic transmission ability,but also ameliorate the physical properties of the material for adapting the stress and strain caused by the volume expansion of silicon in the lithiation and delithiation process.When g-C_(3)N_(4)/Si electrode is evaluated,the initial discharge capacity of g-C_(3)N_(4)/Si nanocomposites is as high as 1033.3 mAh/g at 0.1 A/g,and its reversible capacity is maintained at 548 mAh/g after 400 cycles.Meanwhile,the improved rate capability is achieved with a relatively high reversible specific capacity of 218 mAh/g at 2.0 A/g.The superior lithium storage performances benefit from the unique g-C_(3)N_(4)/Si nanostructure,which improves electroconductivity,reduces volume expansion,and accelerates lithiumion transmission compared to pure silicon.

Recent progress on preparation and applications of layered double hydroxides

The properties of layered double hydroxides(LDHs),including the adjustability of cations in host layers,exchangeability of anions between layers,and tunability of the crystal structure,render them unique characteristics in preparation and applications.Relating to the structural characteristics of LDHs,this work analyzes the research status,advantages and disadvantages of the synthetic methods for LDHs,including hydrothermal,electrodeposition,co-precipitation and anion exchange methods.In addition,the application status and prospects are reviewed,such as photo/electrocatalysis,electrochemical energy storage,magnetic materials,pollutant adsorption,and other fields.Lastly,the critical issues and solutions in the developing process of LDHs are analyzed and proposed.