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.

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.

F127 assisted fabrication of Ge/r GO/CNTs nanocomposites with three-dimensional network structure for efficient lithium storage

To solve the volume expansion and poor electrical conductivity of germanium-based anode materials,Ge/rGO/CNTs nanocomposites with three-dimensional network structure are fabricated through the dispersion of polyethylene-polypropylene glycol(F127)and reduction of hydrogen.An interesting phenomenon is discovered that F127 can break GeO_(2)polycrystalline microparticles into 100 nm nanoparticles by only physical interaction,which promotes the uniform dispersion of GeO_(2)in a carbon network structure composed of graphene(rGO)and carbon nanotubes(CNTs).As evaluated as anode material of Lithium-ion batteries,Ge/rGO/CNTs nanocomposites exhibit excellent lithium storage performance.The initial specific capacity is high to 1549.7 mAh/g at 0.2 A/g,and the reversible capacity still retains972.4 mAh/g after 100 cycles.The improved lithium storage performance is attributed to that Ge nanoparticles can effectively slow down the volume expansion during charge and discharge processes,and threedimensional carbon networks can improve electrical conductivity and accelerate lithium-ion transfer of anode materials.

N/S-Doped Hierarchical Porous Bamboo Carbon Fibers with Ultra-Large Surface Area and Highly Exposed Active Sites for Flexible Zinc-Air Battery

Facile mass transport channel and accessible active sites are crucial for binder-free air electrode catalysts in rechargeable flexible zinc-air battery(ZAB).Herein,a ZnS/NH3 dual-assisted pyrolysis strategy is proposed to prepare N/S-doped hierarchical porous bamboo carbon cloth(HP-NS-BCC)as binder-free air electrode catalyst for ZAB.BCC fabric with abundant micropores is firstly used as flexible carbon support to facilitate the heteroatom-doping and construct the hierarchical porous structure.ZnS nanospheres and NH3 activization together facilitate the electronic modulation of carbon matrix by N/S-doping and optimize the macro/meso/micropores structure of carbon fibers.Benefiting from the highly-exposed N/S-induced sites with enhanced intrinsic activity,the optimized mass transport of biocarbon fibers,as well as the ultra-large specific surface area of 2436.1 m^(2)·g^(-1),the resultant HP-NS-BCC catalyst exhibits improved kinetics for oxygen reduction/evolution reaction.When applied to rechargeable aqueous ZABs,it achieves a significant peak power density of 249.1 mW·cm^(-2).As binder-free air electrode catalyst,the flexible ZAB also displays stable cycling over 500 cycles with a minimal voltage gap of 0.42 V,showcasing promising applications in flexible electronic devices.

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.

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.

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.

Intrinsic Peroxidase-like Activity of Porous CuO Micro-/nanostructures with Clean Surface

Porous CuO micro-/nanostructures with clean surface,prepared through Cu_(2)(OH)_(2)CO_(3) precursor followed by calcination in air,were proven to be an effective peroxidase mimic.They can quickly catalyze oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine(TMB)in the presence of H_(2)O_(2),producing a blue color.The obtained porous CuO micro-/nanostructure have potential application in wastewater treatment.The apparent steady-state kinetic parameter was studied with TMB as the substrate.In addition,the potential application of the porous CuO in wastewater treatment was demonstrated with phenol-containing water as an example.Such investigation not only confirms the intrinsic peroxidase-like activity of micro-/nanostructured CuO,but also suggests its potential application in wastewater treatment.