Etching Mechanism of Ti_(3)C_(2)Cl_(2) MXene Phases by CuCl_(2)-Lewis Molten Salt Method

We described a method for obtaining fluorine-free Ti_(3)C_(2)Cl_(2)MXene phases by melting copper in CuCl_(2)instead of aluminum in Ti_(3)AlC_(2).XRD results show that when molten salt CuCl_(2)etches Ti_(3)AlC_(2),it forms an intermediate product Ti_(3)CuC_(2),and then reacts with Ti_(3)CuC_(2)to obtain Ti_(3)C_(2)Cl_(2).The reaction of Ti_(3)AlC_(2)and CuCl_(2)at a temperature of 800℃for 2 h to obtain Ti_(3)C_(2)Cl_(2)with an optimal lamellar structure is shown in SEM results.The pseudopotential plane-wave(PP-PW)method is used to calculate on the electronic structure.The etching mechanism is investigated by the total energies of each substance.The chemical reaction of Ti_(3)AlC_(2)and CuCl_(2)will first become Ti_(3)CuC_(2)and Cu,and then become Ti_(3)C_(2)Cl_(2)during the Lewis acid etching process,which are consistent with the experimental results.

Low temperature molten salt synthesis of porous La_(1-x)Sr_xMn_(0.8)Fe_(0.2)O_3(0≤x≤0.6) microspheres with high catalytic activity for CO oxidation

A molten salt method was developed to prepare porous La1‐xSrxMn0.8Fe0.2O3 （0≤ x ≤ 0.6） micro‐spheres using hierarchical porous δ‐MnO2 microspheres as a template in eutectic NaNO3‐KNO3. X‐ray diffraction patterns showed that single phase LaMn0.8Fe0.2O3 with good crystallinity was syn‐thesized at 450℃ after 4 h. Transmission electron microscope images exhibited that the LaMn0.8Fe0.2O3 sample obtained at 450？？ after 4 h possessed a porous spherical morphology com‐posed of aggregated nanocrystallites. Field emission scanning electron microscope images indicated that the growth of the porous LaMn0.8Fe0.2O3 microspheres has two stages. SEM pictures showed that a higher calcination temperature than 450？？ had an adverse effect on the formation of a po‐rous spherical structure. The LaMn0.8Fe0.2O3 sample obtained at 450？？ after 4 h displayed a high BET surface area of 55.73 m2/g with a pore size of 9.38 nm. Fourier transform infrared spectra suggested that Sr2＋ions entered the A sites and induced a decrease of the binding energy between Mn and O. The CO conversion with the La1‐xSrxMn0.8Fe0.2O3 （0≤x≤0.6） samples indicated that the La0.4Sr0.6Mn0.8Fe0.2O3 sample had the best catalytic activity and stability. Further analysis by X‐ray photoelectron spectroscopy demonstrated that Sr2＋doping altered the content of Mn4＋ions, oxygen vacancies and adsorbed oxygen species on the surface, which affected the catalytic performance for CO oxidation.

Electrochemical performances of LiFePO_4/C composites prepared by molten salt method

LiFePO4/C composites were synthesized by a molten salt (MS) method using the mixture of LiCl,LiOH and NaCl.The prepared LiFePO4/C composites are characterized by X-ray diffractometry (XRD),field emission scanning electron microscopy (FESEM) and charge-discharge test.XRD patterns indicate that LiFePO4 prepared in the temperature range of 550-700 ℃ crystallizes well in an olivine-type structure.Through FESEM images,the sphere-like and homogeneous particles of 0.2 μm can be observed.The charge-discharge test shows that the materials prepared at 600 ℃ for 12 h have good electrochemical performance.At the rates of 0.2C (34 mA/g) and 0.5C,the discharge capacities are 144.6 and 122.3 mA·h/g,respectively,together with good cycle performances.

Structural and Piezoelectric Properties of Sr_(0.6)Ba_(0.4)Nb_2O_6 Micro-rods Synthesized by Molten-Salt Method

Sr0.6 Ba0.4 Nb2 O6 micro-rods are prepared by the molten-salt method with K2 SO4,KCl-K2 SO4,and KCl as fluxes.It reveals that the Sr0.6 Ba0.4 Nb2 O6 synthesized with KCl as a flux exhibits a single phase with tetragonal tungsten bronze structure.The measurement of X-ray diffraction indicates that the Sr0.6 Ba0.4 Nb2 O6 micro-rods synthesized at 1 300℃are anisotropic.The morphology of the powers is examined by transmission electron microscope.It reveals that the length-diameter ratio of Sr0.6 Ba0.4 Nb2 O6 micro-rods increases with increasing annealing temperature from 900℃to 1 300℃.At 1 300℃,the rod possesses a large length-diameter ratio of 8∶1.Moreover,the analysis of the piezoelectric properties of single micro-rods using apiezo-response force microscope indicates that the domains of the material are arranged along its radial direction.

The potassium storage performance of carbon nanosheets derived from heavy oils

As by-products of petroleum refining,heavy oils are characterized by a high carbon content,low cost and great variability,making them competitive precursors for the anodes of potassium ion batteries(PIBs).However,the relationship between heavy oil composition and potassium storage performance remains unclear.Using heavy oils containing distinct chemical groups as the carbon source,namely fluid catalytic cracking slurry(FCCS),petroleum asphalt(PA)and deoiled asphalt(DOA),three carbon nanosheets(CNS)were prepared through a molten salt method,and used as the anodes for PIBs.The composition of the heavy oil determines the lamellar thicknesses,sp3-C/sp2-C ratio and defect concentration,thereby affecting the potassium storage performance.The high content of aromatic hydrocarbons and moderate amount of heavy component moieties in FCCS produce carbon nanosheets(CNS-FCCS)that have a smaller layer thickness,larger interlayer spacing(0.372 nm),and increased number of folds than in CNS derived from the other three precursors.These features give it faster charge/ion transfer,more potassium storage sites and better reaction kinetics.CNS-FCCS has a remarkable K^(+)storage capacity(248.7 mAh g^(-1) after 100 cycles at 0.1 A g^(-1)),long cycle lifespan(190.8 mAh g^(-1) after 800 cycles at 1.0 A g^(-1))and excellent rate capability,ranking it among the best materials for this application.This work sheds light on the influence of heavy oil composition on carbon structure and electrochemical performance,and provides guidance for the design and development of advanced heavy oil-derived carbon electrodes for PIBs.

Preparation of titanium dioxide from titania-rich slag by molten NaOH method

Preparing titanium dioxide from titania-rich slag （TiO2 73wt%） by molten NaOH method has been developed. The effects of temperature and reaction time on the titanium conversion were investigated. The results showed that temperature had significant influence on the titanium conversion as well as the structure of the product. About 92% of titanium in the titania-rich slag could be converted after reacting with NaOH at 500℃ for 1 h. Metatitanic acid was formed through the steps of washing treatment, acid dissolution, and hydrolysis. Well-dispersed spherical titanium dioxide particles with an average size of 0.1-0.4μm can be obtained by calcination of metatitanic acid. In addition, the content of titanium dioxide in the product is up to 98.6wt%, which can be used as pigments after further treatment of coating and crushing.

Preparation of CeO_(2) abrasives by reducing atmosphere-assisted molten salt method for enhancing their chemical mechanical polishing performance on SiO_(2)substrates

Ce^(3+)as the active site on the CeO_(2)abrasive surface is the key to enhancing the material removal rate(MRR).The CeO_(2)abrasives with high chemical activity were prepared by the molten salt method under a reducing atmosphere.The crystal structure and morphology of CeO_(2)abrasive s were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FT-IR),ultraviolet—visible diffuse reflectance spectroscopy(UV-Vis DRS),and X-ray photoelectron spectroscopy(XPS).The CeO_(2)abrasives were obtained under different atmospheres(Air,Ar,and Ar/H_(2)).With the enhancement of the reducing atmosphere,the morphology of the abrasives transforms from spherical to octahedral,while more oxygen vacancies and Ce^(3+)are generated on the surface of CeO_(2)abrasives.The CMP experiments show that the MRRs of the CeO_(2)-Air,CeO_(2)-Ar,and CeO_(2)-Ar/H_(2)abrasives on SiO_(2)substrates are 337.60,578.74,and 691.28 nm/min,respectively.Moreover,as confirmed by atomic force microscopy(AFM),the substrate surfaces exhibit low roughness(20.5 nm)after being polished using all of the prepared samples.Especially,the MRR of CeO_(2)-Ar/H_(2)abrasives is increased by 104.76%compared with CeO_(2)-air abrasives.The improved CMP performance is attributed to the increased Ce^(3+)concentration and the octahedral morphology of the abrasives enhancing the chemical reaction and mechanical removal at the abrasive-substrate interface.

Fabrication plate-like BaBi_(4)Ti_(4)O_(15) single-crystalline particles by the molten salt synthesis method

Plate-like single-crystalline BaBi_(4)Ti_(4)O_(15) particles were synthesized by the molten salt synthesis(MSS)method.The effects of sintering temperature,holding time,and NaCl-KCl molten salt content on the phase structure and morphology of plate-like BaBi_(4)-Ti_(4)O_(15) particles were investigated.The results show that plate-like BaBi_(4)Ti_(4)O_(15) particles can be synthesized when the sintering temperature is above 800°C.The size of particles increases with increasing sintering temperature and molten salt content.Largely anisotropic plate-like BaBi_(4)Ti_(4)O_(15) particles with diameter≥10μm and thickness of~0.3μm can be obtained under the optimum process parameters.The crystal structure of BaBi_(4)Ti_(4)O_(15) was determined as A21am by TEM,which should be attributed to the Bi3+and Ba2+diffusing into[TiO6]octahedrons.

One-pot molten salt method for constructing CdS/C_(3)N_(4) nanojunctions with highly enhanced photocatalytic performance for hydrogen evolution reaction

The construction of heterojunction photocatalysts for efficiently utilizing solar energy has attracted considerable attention to solve the energy crisis and reduce environmental pollution.In this study,we use the energy released from an easily-occurred exothermic chemical reaction to serve as the drive force to trigger the formation of Cd S and C_(3)N_(4) nanocomposites which are successfully fabricated with cadmium nitrate and thiourea without addition of any solvents and protection of inert gas at initial temperature,a little higher than the melting point of thiourea.The as-prepared Cd S/C_(3)N_(4) materials exhibit high efficiency for photocatalytic hydrogen evolution reaction(HER)with the HER rate as high as 15,866μmol/(g·hr)under visible light irradiation(λ>420 nm),which is 89 and 9 times those of pristine C_(3)N_(4) and Cd S,respectively.Also,the apparent quantum efficiency(AQE)of Cd S/C_(3)N_(4)–1:2–200–2(Cd S/C_(3)N_(4)–1:2–200–2 means the ratio of Cd to S is 1:2 and the reaction temperature is set at 200℃ for two hours)reaches 3.25%atλ=420±15 nm.After irradiated for more than 24 hr,the HER efficiencies of Cd S/C_(3)N_(4) do not exhibit any attenuation.The DFT calculation suggests that the charge difference causes an internal electric field from C_(3)N_(4) pointing to Cd S,which can more effectively promote the transfer of photogenerated electrons from Cd S to C_(3)N_(4).Therefore,most HER should occur on C_(3)N_(4) surface where photogenerated electrons accumulate,which largely protects Cd S from photo-corrosion.

Two tetravalent uranium silicate and germanate crystals with three membered single-ring by molten salt method:K_(2)USi_(3)O_(9)and Cs_(2)UGe_(3)O_(9)

Two tetravalent uranium silicate and germanate M_(2)U^(Ⅳ)T_(3)O_(9)(M=K,Cs;T=Si,Ge)crystals were crystalized under inert gas by molten salt flux growth method.K_(2)USi_(3)O_(9)(1)crystallizes in the monoclinic space group P1_(21)/n1 with lattice parameters a=7.1076?,b=10.4776?,c=12.2957?,γ=120°and V=915.67?^(3).Cs_(2)UGe_(3)O_(9)(2)crystallizes in a hexagonal space group P-6 with lattice constants of a=7.5138?,b=7.5138?,c=11.0114?,γ=120°and V=538.38?^(3).Bond valence calculations indicate tetravalent uranium in both structures,which contain three-membered single-ring T_(3)O_(9)^(6-) trimers.K_(2)USi_(3)O_(9) is the first uranium silicate that contains the Si_(3)O_(9)^(6-) trimers.

Effects of indium doping concentration on the morphology and electrical properties of one-dimensional SnO_2 nanostructures prepared by a molten salt method

In this paper,indium doped SnO2 nanorods and nanowires have been prepared by the molten salt method,and the effects of indium doping concentration on the morphology and electrical properties of one-dimensional(1D) SnO2 nanostructures have been studied.It is found that indium doping concentration can affect the epitaxial growth,morphology and the electrical conductance of 1D SnO2 nanostructures.It is also found that the element made by using 6 mol% indium doped SnO2 nanorods responds to nitrogen gas.

Preparation, Characterizations and Magnetic Properties of Doped Barium Hexaferrites BaFe_(12-2x)Mn_xSn_xO_(19) (x = 0.0-1.0)

A series of doped barium hexaferrites BaFe12-2xMnxSnxO19 （x = 0.0-1.0） particles were prepared by the co-precipitation/molten salt method. The particle size and crystalline of the samples BaFe12-2xMnxSnxO19 decrease with an increase in the doping amount x. When x is less than 0.8, the pure BaFe12-2xMnxSnxO19 particles with hexagonal plate morphology are obtained. The effects of substitution on magnetic properties were evaluated and compared to nomal BaFe12O19. The specific magnetizations （Ms） of doped materials have been significantly improved. Among all these compositions, the BaFe10.4Mn0.8Sn0.8O19 sample has the highest Ms value of 81.8 A？m2？kg-1 at room temperature and its intrinsic coercivity （Hc） is 44.5 kA？m-1. The as-prepared doped barium ferrites exhibit a low temperature coefficient of coercivity close to zero. The coercivity is independent of temperature when x is in the a range 0.5-0.7.

Preparation of Al-Si-Ti Master Alloys by Electrolysis of Silica and Titania in Cryolite-Alumina Melts

Aluminum silicon titanium master alloys were prepared in the laboratory by electrolysis of silica and titania dissolved in cryolite alumina melts. Alloys containing up to 12 mass% Si and 2.6 mass% Ti were formed after about 90 min of electrolysis at 950℃. The current efficiency for the preparation of the Al Si Ti alloys varied with time, temperature and cathodic current density. It is concluded that this electrolytic method may be an interesting alternative to the direct metal mixing process for formation of Al Si Ti master alloys.

MgO/Carbon nanocomposites synthesized in molten salts for catalytic isomerization of glucose to fructose in aqueous media

Isomerization of glucose into fructose has always been an important step in the biorefining process.This study synthesized a novel Mg-decorated carbonaceous catalyst by molten salt method for the application of glucose isomerization.The morphology of carbon microspheres was formed with high specific surface area and pore volume.The effects of Mg loading,catalyst dosage,reaction temperature,and reaction time were investigated and optimized.The highest fructose yield of 34.58%and fructose selectivity of 81.17%were achieved by the catalyst named Mg(100mg)/Carbon at hydrothermal temperature of 100℃ with reaction time of 1.5-2 h,showing the superiority of the catalyst.The results of recycling tests indicated Mg(100mg)/Carbon has good recyclability and can restore its activity after a simple regeneration.And the possible mechanism of glucose isomerization by Mg(100mg)/Carbon was indicated.This study provided a new method for overcoming the difficulty of high energy barrier required for glucose isomerization in the biorefining process.

Enhanced electrochemical performance of nanoscale single crystal NMC811 modification by coating LiNbO_(3)

Single crystallization is an important strategy to resolve intergranular cracks and unnecessary side reactions with electrolytes in layered transition metal oxide cathodes LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)(NMC811).Due to the limitations of high-temperature sintering and multi-step calcination,single crystal NMC811 generally shows irregular particles with a size of 2-3μm.However,the prolonged Li-ion diffusion pathway and the stress generated by the uneven de-/intercalation sluggish Li-ion diffusion kinetics,what is more,cause structural damage such as intragranular cracks.A slow Li extraction rate or particle size reduction will ameliorate the structural damage and improve the cycling stability.As the most promising cathodes for next-generation power batteries,NMC811 required fast charge performance and cycle stability.Particle size reduction appears to be the displacement option.Nanonization is an effective strategy to mitigate intragranular cracks of single crystal NMC811.However,the serious aggregation and increased specific surface area become new challenges.In this article,we synthesized monodisperse nanoscale single crystal NMC811 by molten salt method and modified the surface by LiNbO3 coating.The electrochemical performance shows that nanoscale single crystal NMC811 has faster kinetic and higher capacity retention,so the strategy of combining nanonization and surface coating is an alternative way to prepare high specific capacity and cycle stable single crystal NMC811.

Regulation of the pore structure of carbon nanosheets based electrocatalyst for efficient polysulfides phase conversions

The practical applications of lithium-sulfur(Li-S)batteries are hampered by the sluggish redox kinetics and polysulfides shuttle in the cyclic process,which leads to a series of problems including the loss of active materials and poor cycling efficiency.In this paper,the pore structures of carbon nanosheets based electrocatalysts were precisely controlled by regulating the content of water-soluble KCl template.The relationship between pore structures and Li-S electrochemical behavior was studied,which demonstrates a key influence of pore structure in polysulfides phase conversions.In the liquid-sloid redox reaction of polysulfides,the micropores and small mesopores(d<20 nm)exhibited little impact,while the meso-pores(d>20 nm)and macropores played a decisive role.As a typical exhibition,the nickel-embedded carbon nanosheets(Ni-CNS)with a high content of large mesopores and macropores can aid Li-S batteries in exhibiting stable cycling performance(760.1 mAh g^(-1)at 1 C after 300 cycles)and superior rate capac-ity(847.8 mAh g^(-1)at 2 C).Furthermore,even with high sulfur loading(8 mg cm^(−2))and low electrolyte(E/S is around 6μL mg^(-1)),the high area capacity of 7.7 mAh cm^(−2)at 0.05 C could be achieved.This work can provide a guideline for the design of the pore structure of carbon-based electrocatalysts toward high-efficiency sulfur species redox reactions,and afford a general,controllable,and simple approach to constructing high performance Li-S batteries.

In-situ scalable fast fabrication of Cu-Cu_(2+1)O nanorods for highly efficient electrocatalytic reduction into ammonia under neutral medium

The development of a highly efficient and durable electrocatalyst for nitrate reduction reaction(NO_(3)RR)wastewater valorization to ammonia(NH_(3))is a promising strategy.However,it is challenging to design scalable low-cost electrocatalysts with high activity,high selectivity,and long-term stability by a facile and simple method.Herein,we construct this scalable Cu-based nanoarray with muti-oxidation states grown directly on nickel foam(NF)substrate(Cu_(2+1)O@Cu/NF)using a facile molten salt method combined in-situ electrochemical reduction.The as-prepared Cu_(2+1)O@Cu/NF nanoarrays reveal a high NH_(3) yield of 20.14 mg h^(−1) cm^(−2) at−0.95 V vs.a reversible hydrogen electrode(vs.RHE),Faradaic efficiency of 99.38%at−0.55 V vs.RHE in the neutral potassium phosphate(PBS)buffer solution with 50 mM NaNO_(3),which is ascribed to its electron redistribution with abundant oxygen vacancies and favorable charge/mass transfer.

Experimental and DFT studies of flower-like Ni-doped Mo_(2)C on carbon fiber paper:A highly efficient and robust HER electrocatalyst modulated by Ni(NO_(3))_(2)concentration

Developing highly efficient and stable non-precious metal catalysts for water splitting is urgently required.In this work,we report a facile one-step molten salt method for the preparation of self-supporting Ni-doped Mo_(2)C on carbon fiber paper(Ni–Mo_(2)CCB/CFP)for hydrogen evolution reaction(HER).The effects of nickel nitrate concentration on the phase composition,morphology,and electrocatalytic HER performance of Ni-doped Mo_(2)C@CFP electrocatalysts was investigated.With the continuous increase of Ni(NO_(3))_(2)concentration,the morphology of Mo_(2)C gradually changes from granular to flower-like,providing larger specific surface area and more active sites.Doping nickel(Ni)into the crystal lattice of Mo_(2)C largely reduces the impedance of the electrocatalysts and enhances their electrocatalytic activity.The as-developed Mo_(2)C–3 M Ni(NO_(3))_(2)/CFP electrocatalyst exhibits high catalytic activity with a small overpotential of 56 mV at a current density of 10 mA·cm^(-2).This catalyst has a fast HER kinetics,as demonstrated by a very small Tafel slope of 27.4 mV·dec^(-1),and persistent long-term stability.A further higher Ni concentration had an adverse effect on the electrocatalytic performance.Density functional theory(DFT)calculations further verified the experimental results.Ni doping could reduce the binding energy of Mo–H,facilitating the desorption of the adsorbed hydrogen(Hads)on the surface,thereby improving the intrinsic catalytic activity of Ni-doped Mo_(2)C-based catalysts.Nevertheless,excessive Ni doping would inhibit the catalytic activity of the electrocatalysts.This work not only provides a simple strategy for the facile preparation of non-precious metal electrocatalysts with high catalytic activity,but also unveils the influence mechanism of the Ni doping concentration on the HER performance of the electrocatalysts from the theoretical perspective.