CoB and BN composites enabling integrated adsorption/catalysis to polysulfides for inhibiting shuttle-effect in Li-S batteries

Lithium-sulfur(Li-S)batteries are hampered by the infamous shuttle effect and slow redox kinetics,resulting in rapid capacity decay.Herein,a bifunctional catalysis CoB/BN@rGO with integrated structure and synergy effect between adsorption and catalysis is proposed to solve the above problems.The integrated CoB and BN are simultaneously and uniformly introduced on the rGO substrate through a one-step calcination strategy,applied to modify the cathode side of PP separator.The transition metal borides can catalyze the conversion of lithium polysulfides(Li_(2)Sn,n≥4),whereas the bond of B-S is too weak to absorb LPS.Thus BN introduced can effectively restrict the diffusion of polysulfides via strong chemisorption with LiSnLi+…N,while the rGO substrate ensures smooth electron transfer for redox reaction.Therefore,through the integrated adsorption/catalysis,the shuttle effect is suppressed,the kinetics of redox reaction is enhanced,and the capacity decay is reduced.Using CoB/BN@rGO modified PP separator,the Li-S batteries with high initial capacity(1450 mAh g^(-1)at 0.35 mA cm^(-2))and long-cycle stability(700 cycles at 1.74 mA cm^(-2)with a decay rate of 0.032%per cycle)are achieved.This work provides a novel insight for the preparation of bifunctional catalysis with integrated structure for long-life Li-S batteries.

LiPAA with Short-chain Anion Facilitating Li_(2)S_(x)(x≤4)Reduction in Lean-electrolyte Lithium–sulfur Battery

Lean electrolyte usage in lithium–sulfur battery(LSB)meets the demand of the high energy density.However,lean condition makes the electrolyte-related interface discrete,leading to retardation of ion transfer that depends on interfaces.Consequently,electrochemical reactions face restraint.Herein,lithium polyacrylate acid(LiPAA)with short-chain anions(molecular weight of 2000)is introduced into the cathode.Because of the polysulfide(PS)-philic instinct of the short-chain PAA anions,short-chain PS is captured inside of the cathode.In addition,LiPAA supplies Li^(+)to the short-chain PS captured.The strong interaction between Li_(2)S_(4)and LiPAA effectively decreases Li_(2)S_(4)migration to the anode during discharging.In a sense,the ion mass transfer pattern is thus changed comparing to traditional long-way mode between cathode and anode.Galvanostatic intermittent titration technique(GITT)proves that the interfacial reaction resistance is greatly decreased in the region where Li_(2)S_(x)(x≤4)reduction contributes most.In the same time,the reversibility of electrochemical reduction/oxidation is improved.Owing to the accelerated Li_(2)S_(x)(x≤4)reduction,Li implanting of only 0.3 wt.%plus O introduction up to 1.4 wt.%enables the LSB perform well even with 1/4 of regular electrolyte dosage(5μL mg^(-1))and high-sulfur loading(4.2 mg cm^(-2)),increasing its rate capacity C_(0.8/0.5)from 52.6%(without the LiPAA)to 92.3%(with the LiP AA)as well as a capacity of 518.7 mAh g^(-1)after 400 cycles at 0.8 mA cm^(-2).

Rational design of phosphorus-doped cobalt sulfides electrocatalysts for hydrogen evolution

Moderate anionic doping is an effective approach to improve the performance of electrocatalysts toward hydrogen evolution reaction(HER)since it can adjust the electronic structure,activesite,and phase.The reported studies mainly focus on designing P doped C0S2,while otherphases of cobalt sulfide,such as Co1-xS and Co9S8 doped with P are rarely investigated for HER electrocatalysts.Herein,various cobalt sulfides(including CoSg/Co1-xS,Co1-xS,and Co9S8)doped with P are anchored on carbon cloth through a facile hydrothermal method.Among tested electrocatalysts,P doped Co1-xS exhibits excellent electrocatalytic performance with an overpotential of 110 and 165 mV(vs.RHE)for currentdensities of 10 and 100 mA·cm^-2,respectively.Density functional theory calculations reveal that P doped Co1-xS possesses a smaller bandgapand more optimal hydrogen adsorption sites than pristine Co1-xS.This work initially investigates various cobalt sulfides doped with P and furthergets in sight into the activity improvement mechanism of P dopi ng,which could guide the desig n of earth-abunda nt HER electrocatalysts for the"hydrogen economy".

Subwavelength imaging and detection using adjustable and movable droplet microlenses

We developed adjustable and movable droplet microlenses consisting of a liquid with a high refractive index.The microlenses were prepared via ultrasonic shaking in deionized water,and the diameter of the microlenses ranged from 1 to 50μm.By stretching the microlenses,the focal length can be adjusted from 13 to 25μm.With the assistance of an optical tweezer,controllable assembly and movement of microlens arrays were also realized.The results showed that an imaging system combined with droplet microlenses could image 80 nm beads under white light illumination.Using the droplet microlenses,fluorescence emission at 550 nm from Cd Se@Zn S quantum dots was efficiently excited and collected.Moreover,Raman scattering signals from a silicon wafer were enhanced by^19 times.The presented droplet microlenses may offer new opportunities for flexible liquid devices in subwavelength imaging and detection.

Lipid droplets as endogenous intracellular microlenses

Using a single biological element as a photonic component with well-defined features has become a new intriguing paradigm in biophotonics.Here we show that endogenous lipid droplets in the mature adipose cells can behave as fully biocompatible microlenses to strengthen the ability of microscopic imaging as well as detecting intra-and extracellular signals.By the assistance of biolenses made of the lipid droplets,enhanced fluorescence imaging of cytoskeleton,lysosomes,and adenoviruses has been achieved.At the same time,we demonstrated that the required excitation power can be reduced by up to 73%.The lipidic microlenses are finely manipulated by optical tweezers in order to address targets and perform their real-time imaging inside the cells.An efficient detecting of fluorescence signal of cancer cells in extracellular fluid was accomplished due to the focusing effect of incident light by the lipid droplets.The lipid droplets acting as endogenous intracellular microlenses open the intriguing route for a multifunctional biocompatible optics tool for biosensing,endoscopic imaging,and single-cell diagnosis.

Surface protonation and oxygen evolution activity of epitaxial La(1-x)SrxCoO3 thin films

As an alternative electrode material,transition metal oxides are promising candidates due to multivalent nature and oxygen vacancies present in the structure with facilitate redox reactions.The aim of this study is to explore the intrinsic mechanism of oxygen evolution reaction(OER)using two-dimensional thin film La1-xSrxCoO3 electrode as a model.Herein,we report a planar two-dimensional model La1-xSrxCoO3 electrode grown on a Nb-SrTiO3 single-crystal substrate via pulsed laser deposition.The two-dimensional La1-xSrxCoO3 films offer different oxygen evolution activities at different pH electrolyte solutions.The mechanisms behind the variations of the oxygen evolution activity were discussed after comparing the oxygen evolution activity before and after treatments of the electrodes and measurements by various test methods.The results of this study offer a promising,low-cost electrode material for the efficient OER and a sustainable production of hydrogen fuel.