查看更多>>摘要：Lithium(Li)metal is the most promising elec-trode for next-generation rechargeable batteries.In order to push the commercialization of the lithium metal batteries,a kind of nitrogen(N)-doped composite graphene(NCG)adopted as the Li plating host was prepared to regulate Li metal nucleation and suppress dendrite growth.Further-more,a new kind of sandwich-type composite lithium metal(STCL)electrode was developed to improve its application.The STCL electrode can be used as convenient as a piece of Li foil but no dendrite growth.In a symmetric battery,the STCL electrode cycled for more than 4500 h with the overpotential of less than 40 mV.And due to the creative design,the STCL promises the Li-S battery with a prolonged cycling lifespan.
查看更多>>摘要：Bismuth(Bi),as an alloy-based anode material,has attracted much attention in the development of sodium-ion hybrid capacitors(SIHCs)due to its high theoretical capacity.However,the volume expansion of the Bi-based anode during the sodiation/desodiation process results in limited rate capability.In the present work,a porous Bi-based composite was constructed by a one-step hydrothermal method,and Bi was encapsulated in lignin-derived nitrogen-doped porous carbon(Bi@LNPC)after carbonization.The obtained Bi nanoparticles could effec-tively adapt to the strain and shorten the diffusion distance of Na+.In addition,porous carbon skeleton provides a rigid conductive network for electronic transportation.Therefore,the assembled sodium-ion half-cell with Bi@LNPC anode shows ultra-high-rate capability.When the current density was enhanced from 0.1 to 50 A·g-1,the specific capacity decreased slightly from 351.5 to 342.8 mAh·g-1.Even at an extremely high current density of 200 A·g-1,it retains 81.3％capacity retention when compared to a current density of 1 A·g-1.The SIHCs assembled by Bi@LNPC show a high energy density of 63 Wh·kg-1.This work provides an effective method for developing high-rate Bi anode materials for sodium-ion hybrid capacitors(SIHCs)and sodium-ion batteries(SIBs).
查看更多>>摘要：Exploring wide voltage window materials is not only an available measure to enhance the energy density of hybrid supercapacitor(HSCs),but also avoids the dynamic mismatch caused by different energy storage mechanisms of two electrodes in assembled symmetrical HSC.How-ever,there are few reports about the wide potential window materials except Bi2O3 and VO2.Therefore,the MnF2 synthesized by solvothermal reaction was served as the electrode for HSC.The MnF2 exhibited electrochemical activity in alkaline solution in three-electrode system,especially with a wide potential window from-0.8 to+0.5 V in 2 mol·L-1 NaOH.Furthermore,the assembled MnF2//MnF2 symmetrical HSC had a potential window of 1.5 V,and it exhibited outstanding long-cycle capability.Meanwhile,when MnF2 was taken as the negative and positive respectively,the potential windows of asymmetric devices CoMoO4//MnF2 and MnF2//Activated Carbon(AC)could reach 1.3 and 1.45 V,respectively,showing excellent cycle stability.This work shows that MnF2 material has great research value in HSC,and provides a new research direction for developing high-performance devices.
查看更多>>摘要：The synthesis of a perpendicular growth struc-ture of MoS2 nanosheets on graphene for efficient sodium storage is challenging yet ideal due to the benefits of open ion diffusion channels and high electronic conductivity.In this study,we have successfully fabricated a novel struc-ture of vertical MoS2 nanosheets on graphene,with ZnS nanoparticles serving as bonding points(MoS2/ZnS/G),through a facile hydrothermal method.During the synthesis process,Zn2+not only acts as a landing site for the vertical growth of MoS2 nanosheets but also triggers the formation of a defect-rich structure in the final samples.This unique architecture of MoS2/ZnS/G effectively combines the advantages of a vertically aligned geometry and a defect-rich structure for energy storage.The resulting structure displays shortened transport paths for electrons/ions,enhanced conductivity,improved structural integrity,and an increased number of active sites for promising electro-chemical performance.As expected,when used as anode for sodium-ion batteries,the as-synthesized MoS2/ZnS/G exhibits excellent rate capability(high capacity of 298 mAh·g-1 at 5 A·g-1)and good cycling stability(a capacity decay of 0.056％per cycle after 500 cycles at 1 A·g-1).According to the kinetic investigations,the electrochemical process of the MoS2/ZnS/G sample is primarily governed by a pseudocapacitive behavior,which enhances the charge/discharge kinetics and allows the MoS2/ZnS/G structure to remain intact during cycling.
查看更多>>摘要：An efficient electrocatalyst is indispensable to significantly reduce energy consumption and accelerate the conversion efficiency of water splitting.In this work,the honeycomb-like porous MoCo alloy on nitrogen-doped three-dimensional(3D)porous graphene substrate(Mo0.3Co0.7@NPG)has been synthesized from the annealing of layered double hydroxide(MoCo-LDH@NPG).Especially,the Mo0.3Co0.7@NPG exhibits low hydrogen evolution overpotential of 75 mV(10 mA.cmr-2)and a Tafel slope of 69.9 mV·dec-1,which can be attributed to highly conductive NPG substrate,the unique nanostructure and the synergistic effect of Mo and Co.Moreover,the Mo0.3Co0.7@NPG can maintain the original morphology and high catalytic activity after 50-h stability test.This work proposes a general strategy to synthesize a multi-element alloy on conductive substrates with high porosity for electrocatalytic reaction.
查看更多>>摘要：Metal-organic frameworks(MOFs)have attracted widespread attention due to their large surface area and porous structure.Rationally designing the nanostructures of MOFs to promote their application in ethanol electrooxidation is still a challenge.Here,a novel Cu-NCNs(Cu-nitrogen-doped carbon nanotubes)support was synthesized by pyrolysis of melamine(MEL)and Cu-ZIF-8 together,and then,Pd-Au nanoalloys were loaded by sodium borohydride reduction method to prepare PdAu@Cu-NCNs catalysts.The generating mesoporous carbon with high specific surface area and favorable elec-tron and mass transport can be used as a potential excellent carrier for PdAu nanoparticles.In addition,the balance of catalyst composition and surface structure was tuned by controlling the content of Pd and Au.Thus,the best-per-formed Pd2Au2@Cu-NCN-1000-2(where 1000 means the carrier calcination temperature,and 2 means the calcina-tion constant temperature time)catalyst exhibits better long-term stability and electrochemical activity for ethanol oxidation in alkaline media(4.80 A·mg-1),which is 5.05 times higher than that of commercial Pd/C(0.95 A·mg-1).Therefore,this work is beneficial to further promoting the application of MOFs in direct ethanol fuel cells(DEFCs)and can be used as inspiration for the design of more efficient catalyst support structures.
查看更多>>摘要：Electrocatalytic water splitting coupled with sustainable energies is identified as an environmentally friendly and renewable strategy to generate high-quality hydrogen for the fuel cells.However,the main challenge is to develop high performance,low cost and chemically stable electrocatalysts to decline the energy barriers and enhance the sluggish kinetics of hydrogen evolution reac-tion(HER).Herein,a three-dimensional hierarchically ordered macroporous Ru-CoP@NC electrocatalyst(3DOM Ru-CoP@NC)derived from ordered macro-microporous metal-organic frameworks has been prepared using the precursor@template and double-solvent methods.The prepared 3DOM Ru-CoP@NC catalyst exhibits an overpotential of 15 mV(j=10 mA·cm-2)and a reaction Tafel slope of 38 mV.dec-1 in alkaline electrolyte,which are superior to commercial Pt@C catalyst.Additionally,the overpotential and reaction Tafel slope of this catalyst in acidic media are 45 mV and 50 mV·dec-1,respectively.The outstanding HER activities of 3DOM Ru-CoP@NC catalysts are ascribed to the 3D highly interconnected-reticular nanospaces that can increase effective reaction active sites.The N doped carbon framework improves the electronic properties and conductivity.Moreover,the strong interaction of Ru and CoP nanoparticles also boosts the HER process.These results indicate that 3DOM Ru-CoP@NC catalysts with high catalytic activities have a broad application prospect in the future.
查看更多>>摘要：As an effective strategy to improve the prop-erties of electrocatalysts,magnetic field-assisted electro-catalytic water splitting has attracted increasing attention recently.However,the corresponding enhancements mostly depend on the exertion of an external magnetic field during electrochemical reactions,which results in a high cost of industrial production,and makes the magnetic field manipulation of electrocatalysis become a challenging task.In this work,instead of the external magnetic field,a bias magnetic field is self-supplied by the remanence state of a ferromagnetic electrocatalyst of FePt.Owing to the assistance of this bias magnetic field,the FePt film in the remanence state shows the overpotential of 229 mV during hydrogen evolution reaction,which is much lower than that in its demagnetization state(283 mV).Our findings demonstrate that the remanence in ferromagnetic electro-catalysts can improve the catalytic performance,which is attributed to the decrease in domain walls.
查看更多>>摘要：Photocatalytic reductive amination of biomass-derived aldehydes is a desirable way to selectively upgrade biomass into value-added nitrogen-containing chemicals under mild conditions.However,it is challenging to pro-duce imines in high selectivity because of the undesirable side reactions caused by the activity of functional groups.Here,we demonstrate the highly reactive and selective production of imines from biomass derived aldehydes via the photocatalytic reductive amination,using a defective TiO2 supported nickel catalyst.The employment of methanol as the hydrogen donor and ammonia solution as the nitrogen source avoids the use of high-pressure H2 and expensive amines,rendering the current catalytic process safe,economical,and environmentally friendly.In depth investigations attribute the improved separation and trans-fer of photogenerated charge carriers to the presence of oxygen vacancies and decorated Ni nanoparticles,thereby accelerating the production of imines from benzaldehyde amination(conversion,95.8％;selectivity,95.2％).Fur-thermore,the developed system could be easily translated to the photocatalytic conversions of various biomass derived aldehydes,which provided an example of a cost-effective and sustainable approach for the valorization of biomass derived feedstocks.
查看更多>>摘要：At present,industrial synthetic ammonia was still obtained through the Hubble-Bosch process,with large energy consumption.It is a research hotspot to realize green synthetic ammonia by using solar energy.The dif-ficulty of photocatalytic ammonia synthesis was that the photo-excited electrons have not enough energy to active N ≡ N.In this study,Ti was doped into BiOBr by one-step hydrothermal method,which was oxidized into TiO2 when the doping amount reaches the maximum,in situ forming Ti0.31B0.69OB/TiO2 composites.Benefiting from the syn-ergistic effect of Ti doping and S-scheme heterojunction,the synthetic ammonia efficiency of Ti0.31B0.69OB/TiO2-11.96 reached 1.643 mmol·g-1cat at mild conditions and without hole scavenger for up to 7 h,the efficiency of synthetic ammonia is 115 times,10.5 times and 3.3 times of that of BiOBr,Ti0.31B0.69OB and TiO2,respectively.Specifically,DFT calculation confirms that Ti doping accurately refine the electronic structure of BiOBr,facili-tate nitrogen adsorption activation and reduce hydrogena-tion reaction energy barrier,thus accelerating the reaction kinetics of photocatalytic nitrogen reduction(NRR).Meanwhile,constructing S-scheme heterojunction boosts the separation and transfer of photogenerated electron-hole pairs,improving the reduction ability of electrons in the conduction band of TiO2 and the oxidation ability of holes in the valence band of Ti0.31B0.69OB.
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