Emerging perovskite materials for supercapacitors:Structure,synthesis,modification,advanced characterization,theoretical calculation and electrochemical performance

As a new generation electrode materials for energy storage,perovskites have attracted wide attention because of their unique crystal structure,reversible active sites,rich oxygen vacancies,and good stability.In this review,the design and engineering progress of perovskite materials for supercapacitors(SCs)in recent years is summarized.Specifically,the review will focus on four types of perovskites,perovskite oxides,halide perovskites,fluoride perovskites,and multi-perovskites,within the context of their intrinsic structure and corresponding electrochemical performance.A series of experimental variables,such as synthesis,crystal structure,and electrochemical reaction mechanism,will be carefully analyzed by combining various advanced characterization techniques and theoretical calculations.The applications of these materials as electrodes are then featured for various SCs.Finally,we look forward to the prospects and challenges of perovskite-type SCs electrodes,as well as the future research direction.

Enhancing effect of choline chloride-based deep eutectic solvents with polyols on the aqueous solubility of curcumin–insight from experiment and theoretical calculation

The development of green solvents for enhancing aqueous solubility of drug curcumin remains a challenge. This study explores the enhancing effect of deep eutectic solvents(DESs) on the aqueous solubility of curcumin(CUR) via experiment and theoretical calculation. Choline chloride-based DESs with polyols 1,2-propanediol(1,2-PDO), 1,3-propanediol, ethylene glycol, and glycerol as hydrogen bond donors were prepared and used as co-solvents. The CUR aqueous solubility increased with increasing the DESs content at temperature of 303.15-318.15 K, especially in aqueous ChCl/1,2-PDO(mole ratio 1:4) solutions. The positive apparent molar volume values and reduced density gradient analysis confirmed the existence of strong interactions between CUR and solvent. The van der Waals interactions and hydrogen bonding coexisted in DESs monomer retained the stability of DESs structure after introducing CUR. Moreover,the lower interaction energy of DESs…CUR system than that of the counterpart DESs further proved the strong interaction between CUR and DESs. The lowest interaction energy of ChCl/1,2-PDO…CUR system indicated that this system was the most stable and ChCl/1,2-PDO was promising for CUR dissolution.This work provides efficient solvents for utilizing curcumin, contributing to a deep insight into the interactions between DES and CUR at the molecular level, and the role of DESs on enhancing drugs solubility.

Precision tuning of highly efficient Pt-based ternary alloys on nitrogen-doped multi-wall carbon nanotubes for methanol oxidation reaction

The electrochemical methanol oxidation is a crucial reaction in the conversion of renewable energy.To enable the widespread adoption of direct methanol fuel cells(DMFCs),it is essential to create and engineer catalysts that are both highly effective and robust for conducting the methanol oxidation reaction(MOR).In this work,trimetallic PtCoRu electrocatalysts on nitrogen-doped carbon and multi-wall carbon nanotubes(PtCoRu@NC/MWCNTs)were prepared through a two-pot synthetic strategy.The acceleration of CO oxidation to CO_(2) and the blocking of CO reduction on adjacent Pt active sites were attributed to the crucial role played by cobalt atoms in the as-prepared electrocatalysts.The precise control of Co atoms loading was achieved through precursor stoichiometry.Various physicochemical techniques were employed to analyze the morphology,element composition,and electronic state of the catalyst.Electrochemical investigations and theoretical calculations confirmed that the Pt_(1)Co_(3)Ru_(1)@NC/MWCNTs exhibit excellent electrocatalytic performance and durability for the process of MOR.The enhanced MOR activity can be attributed to the synergistic effect between the multiple elements resulting from precisely controlled Co loading content on surface of the electrocatalyst,which facilitates efficient charge transfer.This interaction between the multiple components also modifies the electronic structures of active sites,thereby promoting the conversion of intermediates and accelerating the MOR process.Thus,achieving precise control over Co loading in PtCoRu@NC/MWCNTs would enable the development of high-performance catalysts for DMFCs.

Progress in Mechanical Modeling of Implantable Flexible Neural Probes

Implanted neural probes can detect weak discharges of neurons in the brain by piercing soft brain tissue,thus as important tools for brain science research,as well as diagnosis and treatment of brain diseases.However,the rigid neural probes,such as Utah arrays,Michigan probes,and metal microfilament electrodes,are mechanically unmatched with brain tissue and are prone to rejection and glial scarring after implantation,which leads to a significant degradation in the signal quality with the implantation time.In recent years,flexible neural electrodes are rapidly developed with less damage to biological tissues,excellent biocompatibility,and mechanical compliance to alleviate scarring.Among them,the mechanical modeling is important for the optimization of the structure and the implantation process.In this review,the theoretical calculation of the flexible neural probes is firstly summarized with the processes of buckling,insertion,and relative interaction with soft brain tissue for flexible probes from outside to inside.Then,the corresponding mechanical simulation methods are organized considering multiple impact factors to realize minimally invasive implantation.Finally,the technical difficulties and future trends of mechanical modeling are discussed for the next-generation flexible neural probes,which is critical to realize low-invasiveness and long-term coexistence in vivo.

Theoretical Calculation Model of Heat Transfer for Deep-derived Supercritical Fluids with a Case Study

Based on a set of equations established by Duan et al. (1992, 1996) for a geofluid system H2O-CO2-CH4(-N2), a formula is obtained to calculate the heat changes. Combining the geological T-P conditions (geothermal gradients and lithostatic and hydrostatic pressures), the enthalpy of some typical geofluids is figured out. Then the principles of heat transfer of deep-derived supercritical fluids are discussed. The result shows that deep-derived geofluids can bring a large amount of thermal heat and release most heat to the shallow surroundings as they move up, because the molar enthalpies vary very greatly from the deep to shallow, increasing with the increases of T and P. Generally, more than tens of kilojoules heat per molar can be released. Furthermore, the molar enthalpy is affected by the compositions of the geofluids, and the molar enthalpy of CO2, CH4, or N2 is greater than that of H2O, being twice, more than twice, and about 140% of H2O, respectively. Finally, a case study is conducted by investigating a source rock sequence affected hydrothermally by magmatic fluids in the Huimin depression of Shengli Oilfield. The thermal heat calculated theoretically of the fluids related to a diabase intrusion is quite large, which can increase the temperature near the diabase to about 300℃, and that can, to some extent, account for the abnormal rise of the vitrinite reflectance, with the highest of about 3.8% (Ro).

Theoretical and numerical simulation study on jet formation and penetration of different liner structures driven by electromagnetic pressure

The use of a shaped liner driven by electromagnetic force is a new means of forming jets. To study the mechanism of jet formation driven by electromagnetic force, we considered the current skin effect and the characteristics of electromagnetic loading and established a coupling model of "ElectriceMagnetic eForce" and the theoretical model of jet formation under electromagnetic force. The jet formation and penetration of conical and trumpet liners have been calculated. Then, a numerical simulation of liner collapse under electromagnetic force, jet generation, and the stretching motion were performed using an ANSYS multiphysics processor. The calculated jet velocity, jet shape, and depth of penetration were consistent with the experimental results, with a relative error of less than 10%. In addition, we calculated the jet formation of different curvature trumpet liners driven by the same loading condition and obtained the influence rule of the curvature of the liner on jet formation. Results show that the theoretical model and the ANSYS multiphysics numerical method can effectively calculate the jet formation of liners driven by electromagnetic force, and in a certain range, the greater the curvature of the liner is, the greater the jet velocity is.

A New One-dimensional Coordination Polymer Based on 3,5-Dinitro-salicylic Acid:Synthesis,Crystal Structure,Luminescent Property and Theoretical Calculation

A new one-dimensional Mg（Ⅱ） coordination polymer, [Mg（L）（phen）（H2O）]（1）, has been hydrothermally synthesized by using 3,5-dinitro-salicylic acid（H2L） and 1,10-phenanthroline（phen）. It crystallizes in monoclinic, space group C2/c with a = 33.038（7）, b = 6.6481（13）, c = 22.750（5） A, β = 126.99（3）°, V = 3991.1（14） A3, Z = 8, C19H12 MgN4O8, Mr = 448.64, Dc = 1.493 g/cm3, F（000） = 1840, μ（Mo Ka） = 0.146 mm-1, R = 0.0559 and w R = 0.0975. In 1, each L anion bridges two Mg（Ⅱ） atoms to give one-dimensional zigzag chains with the Mg…Mg separation of 5.34 ？, which are extended by π-π stacking interactions between 1,10-phenanthroline ligands into a two-dimensional supramolecular layer. Moreover, the O–H…O hydrogen-bonding interactions further stabilize the layer structure of 1. The luminescent property was also studied for 1 in solid state at room temperature. In addition, natural bond orbital（NBO） analysis was performed by the B3LYP/LANL2 DZ method in Gaussian 09 Program. The calculation results show obvious covalent interaction between the coordinated atoms and Mg（Ⅱ） ion.

Experimental and Theoretical Study on Bonding Properties between Steel Bar and Bamboo Scrimber

To further verify the feasibility of newly designed reinforced bamboo scrimber composite(RBSC)beams used in building construction,the bonding properties between steel bar and bamboo scrimber were investigated by anti-pulling tests.Results indicated that the anti-pulling mechanical properties were significantly correlated to the diameter,thread form and buried depth of steel bar,forming density of bamboo scrimber as well as the heat treatment of bamboo bundle.There were two failure modes for anti-pulling tests:the tensile fracture and pulling out of steel bar.Both the ultimate load and average shear strength of anti-pulling specimen could be increased greatly with the ribbed bar,high forming density of bamboo scrimber and un-heated bamboo bundle.Furthermore,a theoretical calculation model of the bonding interface between steel bar and bamboo scrimber was developed.Based on the theoretical calculation model,the change laws of normal stress of bamboo scrimber,and shear stress of glue layer along the buried depth of steel bar were revealed.This study is beneficial for the safety application of RBSC beams in building construction.

Synthesis, Crystal Structure and Theoretical Calculation of a Novel 2D Network of Manganese(Ⅱ) Complex

A novel complex, [Mn(2-NCP)(H2BTC)(H2O)]n(1, 1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid, 2-HNCP = 2-(2-carboxyphenyl)-1 H-imidazo(4,5-f)-(1,10)phenanthroline), was hydrothermally synthesized and structurally characterized by elemental analysis, IR, XRD and single-crystal X-ray diffraction. Structural analyses reveal that complex 1 exhibits a(6, 6)-connected topology network with a Schlafli symbol of(6^3). The adjacent 2D layers are further stacked via strong hydrogen-bonding interactions, giving a 3 D supramolecular framework. In addition, the structure of complex 1 was calculated by the B3LYP/LANL2 DZ method by Gaussian program. The results from natural bond orbital(NBO) analysis shows obvious covalent interaction between the coordinated atoms and Mn(Ⅱ) ion.

Synthesis, Crystal Structure and Theoretical Calculation of [2-(2,6-Dioxacyclohexyl)-5-methoxylphenols]_2

The title compound [2-（2,6-dioxacyclohexyl）-5-methoxylphenols]2 was synthesized by the reaction of 2-hydroxyl-3-methoxylbenzaldehyde and 1,3-propanediol in the presence of DMF-DMS adduct and characterized by IR spectrum, UV-Vis spectrum and X-ray crystallography. The title compound belongs to monoclinic, space group P21 with a = 9.8967（10）, b = 8.2240（9）, c = 13.3654（14） A^°, β= 90.016（2）°, C11H14O4, Mr = 210.22, V = 1087.8（2）A^°3, Z = 4, Dc = 1.284 Mg/m^3, F（000） = 448,μ = 0.098 mm^-1, the final R = 0.0300 and wR = 0.0761 for 2070 observed reflections with I 〉 2σ（I）. The molecules are connected via intermolecular O-H…O hydrogen bonds into a 2D network structure. Moreover, theoretical investigations of the title compound with HF/6-31G（d） method were performed, and its stability, frontier molecular orbital composition and Mulliken charge distribution were also discussed. The compound is a bis-molecule. The two molecules stay together and could not be separated. Two crystallographically independent molecules exist in an asymmetric unit. The bond lengths and bond angles of the two molecules are slightly different with each other.

Synthesis,Crystal Structure,Theoretical Calculations,and Photoluminescent Property of a Mn(Ⅱ)Complex Assembled by 5-Aminoisophthalic Acid and Phen Ligands

A coordination polymer [Mn2（ctpt）2（aic）2]n （1, ctpt = 2-（4-chloro-phenyl）-1H- 1,3,7,8-tetraaza-cyclopenta[l]phenanthrene, H2aic = 5-amino-isophthalic acid） was hydrother- mally designed and synthesized. The complex was characterized by elemental analysis, IR spectro- scopy, single-crystal X-ray diffraction, and thermogravimetric analysis （TGA）. Each Mn（II） atom is linked by the aic ligands with neighbor Mn（II） atoms, forming an infinite one-dimensional （1D） double-chain structure. Complex 1 crystallizes in monoclinic, space group C2/c, with a = 18.23（1）, b = 17.27（1）, c = 16.69（1） ？, V = 4814.0（7） ？3, C27H16ClMnN5O4, Mr = 564.84, Dc = 1.559 g/cm3, μ（MoKα） = 0.706 mm-1, F（000） = 2296, Z = 8, the final R = 0.0487 and wR = 0.1269 （I 〉 2σ（I））. The 1D chain structure of complex 1 is stable below 458 ℃. In addition, to elucidate the essential electronic characters of this complex, theoretical calculation analysis of 1 was performed by the PBE0/LANL2DZ method in Gaussian 03 Program.

Synthesis, Structure and Theoretical Calculation of Imidazolium 3,5-Dinitrobenzoate

The title adduct imidazolium 3,5-dinitrobenzoate has been synthesized in aqueous solution and characterized by elemental analyses, IR spectrum and X-ray crystallography. The title compound belongs to monoclinic, space group P21/n with a = 7.5540（9）, b = 21.333（2）, c = 7.7823（9）A, β = 102.741（2）^o, C10H8N4O6, Mr = 280.20, V= 1223.3（2）A^3, Z = 4, Dc = 1.521 g/cm^3, F（000） = 576, p = 0.129 mm^-1, the final R = 0.0433 and wR = 0.1092 for 2001 observed reflections with I 〉 2a（I）. The structural analysis indicates the component ions are linked by N-H...O hydrogen bonds into an infinite one-dimensional C2^2 （8） chain parallel to the [1 0 -1] direction. Moreover, the theoretical investigations of the title compound with HF/6-31G（d） method were performed, and its stability, frontier molecular orbital composition and Mulliken charge distribution were also discussed.

Synthesis, Crystal Structure and Theoretically Study of 2-(Dimethylamino)-1,3-dithiocyanatopropane and Its Isomer

2-（Dimethylamino）-1,3-dithiocyanatopropane（1） has been prepared as a key intermediate synthesizing a natural insecticide Cartap by the reaction of 1-dimethylamino-2,3-dichloropropane with sodium thiocyanate. The crystal structures of compound 1 and its isomer 1-（dimethylamino）-2,3-dithiocyanotopropane（2） formed during the reaction were determined by X-ray single-crystal diffraction. Bond lengths in both the compounds are common and fall within normal ranges. There are some weak C―H×××N hydrogen bonds in the lattice of compound 1, which makes it form a three-dimensional network, which stabilize the crystal structure. No classic hydrogen bonds were founded in its isomer（2）, only van der Waals forces contribute to the stability of the structure. In addition, DFT and MP2 calculations with 6-311＋G（d, p） basis set have also been carried out to investigate the thermodynamic properties of compounds 1 and 2. The research will be applied to the further investigation of the tautomerization of compounds 1 and 2.

Theoretical Chemistry Study of the Hydrogen-bonded Interaction between Acylamine and Chloromethane Compounds

The hydrogen-bonded interaction between acylamine and chloromethane was studied using theoretical calculation methods. Looking the interaction system as a hydrogen-bonded complex, the geometric optimization of the interaction system was performed with HF and B3LYP methods at 6-311＋＋G^＊＊ level. Stable structures of these complexes were obtained. Binding energies and some other physical chemistry parameters of them were computed and compared. According to the calculation results, it can be identified that DMA （DMF or DEF） can form stable complex with chloromethane by the hydrogen-bonded interaction between them. The stable orders of these hydrogen-bonded complexes were obtained and described as： DMF-CHCl3〉DMF-CH2Cl2〉 DMF-CH3Cl, DEF-CHCl3 〉 DEF-CH2Cl2 〉 DEF-CH3Cl, DMA-CHCl3 〉 DMA-CH2Cl2 〉 DMA-CH3Cl, respectively.

Synthesis, Structure, Luminescence and Theoretical Investigations on a New Tin Complex with (2,3-f)-pyrazino(1,10)phenanthroline-2,3-dicarboxylic Acid

A new tin complex Sn（CH3HPPDA）Ch （1） was prepared from SnCh＇5H2O with （2,3-f）-pyrazino（1,10）phenanthroline-2,3-dicarboxylic acid （H2PPDA） by solvothermal reaction in methanol, and characterized by single-crystal X-ray diffraction analysis, optical absorption spectrum and photoluminescence. Compound 1 crystallizes in a monoclinic centrosymmetric space group of P21/c with a = 12.418（2）, b = 11.9467（12）, c = 15.845（3） A, β= 107.948（7）°, V= 2236.2（6） A3, Z = 4, Mr = 594.78, D, = 1.767 g/cm3, μ= 1.651 mm-1, F（000） = 1160, S= 1.023 and T= 293（2） K. The final R = 0.0847 and wR = 0.2431 for 3144 observed reflections with 1 〉 2σ（I）. The discrete mononuclear Sn（CH3HPPDA）CI4 complex is connected into a supramolecular network of 1 by intramolecular and intermolecular C-H...C1 and intermolecular C-H……O hydrogen bonding interactions. Compound 1 displays fluorescence with a lifetime value of about 7.58 ns in the visible region under visible-light excitation, and the origin of the luminescent emission is primarily assigned to the combination of intraligand charge-transfer of CH3HPPDA and C1-to-CH3HPPDA charge-transfer mechanism which is probed by the density of states （DOS） calculations.

Blue-emissions Modulated by Packing Forces in Alkaline-earth Metal OrganicFrameworks Based on Thiophene-2,5-dicarboxylic: Structures and Theoretical Calculations

Solvothermal reactions of Ca(NO), Sr(NO)with thiophene-2,5-dicarboxylic in DMF afforded two new inorganic-organic hybrid frameworks, [M(TDC)(DMF)]n(M = Ca(1), Sr(2), TDC = thiophene-2,5-dicarboxylic, DMF = N,N?-dimethylformamide), which have been characterized by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analysis and IR spectra. Both compounds feature three-dimensional(3D) frameworks based on the versatile coordinated modes(μ-η~2:η~2, μ-η~2:η~1, μ-η~2:η~1) of carboxylic groups in tdc ligands. C–H···S hydrogen bonds and C–H···π interactions contribute to the stabilization of the structures. They exhibit weaker packing force compared with their literature isomers. Consequently, blue and blue/green luminescence of two compounds has been observed. Their luminescence mechanism can be ascribed to ligand-to-metal charge transfer(LMCT) compared with the ligand-centered luminescence in their isomers. Electronic structural calculations illustrate that under the condition of weaker packing forces, larger gaps can be achieved, which facilitate the LMCT. This work suggests that the introduction of S-heteroatom can result in more electrons rich in the metal centers, thus giving rise to metal-involved luminescence.

Heterostructured bimetallic phosphide nanowire arrays with latticetorsion interfaces for efficient overall water splitting

Designing cost-effective and high-efficiency electrocatalysts is critical to the water splitting performance during hydrogen generation.Herein,we have developed Fe_(2)P-Co_(2)P heterostructure nanowire arrays with excellent lattice torsions and grain boundaries for highly efficient water splitting.According to the microstructural investigations and theoretical calculations,the lattice torsion interface not only contributes to the exposure of more active sites but also effectively tunes the adsorption energy of hydrogen/oxygen intermediates via the accumulation of charge redistribution.As a result,the Fe_(2)P-Co_(2)P heterostructure nanowire array exhibits exceptional bifunctional catalytic activity with overpotentials of 65 and 198 mV at 10 mA cm^(-2) for hydrogen and oxygen evolution reactions,respectively.Moreover,the Fe_(2)P-Co_(2)P/NF-assembled electrolyzer can deliver 10 mA cm^(-2) at an ultralow voltage of1.51 V while resulting in a high solar-to-hydrogen conversion efficiency of 19.8%in the solar-driven water electrolysis cell.

Effect of homojunction structure in boosting sodium-ion storage: The case of MoO_(2)

High-efficiency sodium-ion batteries(SIBs) are in great demand for energy storage applications,which are dominated by the Na+storage performance of electrode materials.Here,a one-pot solvothermal method is developed to construct amorphous/crystalline MoO_(2)(a/c-MoO_(2)) homojunction for boosting Na+storage.Theoretical simulations signify that electrons redistribute at the homogenous interface of a/c-MoO_(2),resulting in an inbuilt driving force to easily adsorb charge carriers and promote the electron/ion transfer ability.Relying on its crystallographic superiorities,the a/c-MoO_(2)homojunction with high Na adsorbability(-1.61 eV) and low Na diffusion energy barrier(0.519 eV) achieves higher capacity(307 mA h g^(-1)at 0.1 A/g),better rate capability and cycling stability than either a-MoO_(2)or c-MoO_(2)counterpart.Combining in-situ X-ray diffraction(XRD) and ex-situ X-ray photoelectron spectroscopy(XPS)techniques,the ’adsorption-insertion-conversion’ mechanism is well established for Na+storage of MoO_(2).Our work opens new opportunities to optimize electrode materials via crystallographic engineering for efficient Na+storage,and helps to better understand the effects of homojunction structure in enhanced electrochemical performance.

Damage-ignition mechanism studies on modified propellant with different crosslinking density under dynamic loading

The study of high-energy and low-vulnerability propellants is important for the power performance and safety of solid propellant rocket motors.The modified split Hopkinson pressure bar(SHPB)tests are performed on two kinds of propellant with different crosslinking density to study the dynamic mechanical responses and damage-ignition mechanism.SHPB apparatus is equipped with a highperformance infrared camera and high-speed camera to capture the deformation,damage-ignition feature and temperature evolution images in the impact process.The results suggested that the mechanical responses and damage-ignition mechanism of the propellants were affected by the strain rates and crosslinking density.The damage-ignition degree is more intense and the reaction occurs earlier with the increase of strain rates.For propellant 1 with higher crosslinking density,the critical ignition strain rate is 4500 s^(-1).Two kinds of propellants show different ignition mechanism,i.e.crack generation,propagation and final fracture for propellant 1 while viscous shear flow for propellant 2.Meanwhile,the SEM images also reveal the difference of damage-ignition mechanism of the two kinds of propellants.Finally,the ignition mechanism under different strain rates and critical ignition strain rate of propellants are further explained by the theoretical calculation of temperature variations.

Alternative lead-free mixed-valence double perovskites for high-efficiency photovoltaic applications

Lead-based organic-inorganic hybrid perovskites have exhibited great potential in photovoltaics,achieving power conversion efficiencies(PCEs) exceeding 25%.However,the toxicity of lead and the instability of these materials under moist conditions pose significant barriers to large-scale production.To overcome these limitations,researchers have proposed mixed-valence double perovskites,where Cs_(2)Au~ⅠAu~ⅢI_6 is a particularly effective absorber due to its suitable band gap and high absorptance efficiency.To further extend the scope of these lead-free materials,we varied the trivalent gold ion and halogen anion in Cs_(2)Au~ⅠAu~ⅢI_6,resulting in 18 new structures with unique properties.Further,using first-principles calculations and elimination criteria,we identified four materials with ideal band gaps,small effective carrier mass,and strong anisotropic optical properties.According to theoretical modeling,Cs_(2)AuSbCl_6,Cs_(2)AuInCl_6,and Cs_(2)AuBiCl_6 are potential candidates for solar cell absorbers,with a spectroscopic limited maximum efficiency(SLME) of approximately 30% in a 0.25 μm-thick film.These three compounds have not been previously reported,and therefore,our work provides new insights into potential materials for solar energy conversion.We aim for this theoretical exploration of novel perovskites to guide future experiments and accelerate the development of high-performance photovoltaic devices.