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.

Theoretical study on anomalous thermal expansion of two AB_(2)-type compounds

Anomalous thermal expansion,or other words,negative thermal expansion(NTE),resulting from the lattice contraction upon temperature increasing,has been an enduring topic for material science and engineering.The variation of a lattice go with the temperature is straightly originated from its electronic structures and is inseparable from those physical properties.In the past several decades,many efforts have been made to searching new series of NTE compounds or control the thermal expansion performance in order to supply various demands of different extreme applications.These development of new NTE systems also dependences on the theoretical studies.Here,we carried out theoretical calculation on CrB_(2) and FeZr_(2) with anisotropic negative thermal expansion.Intriguingly,theoretical calculations reveal that the binding of either Cr-Cr pair or Fe-Fe pair is relatively small.The results reveal that the origin of NTE is the ordered magnetic state during the increasing of temperature.The localized electrons would prevent the lattice parameters increase with heating,which shows macroscopic NTE phenomenon.

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).

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.

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 Schl?fli symbol of（63）. The adjacent 2 D 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.

A New Cd(Ⅱ) Coordination Polymer Constructed by 1,10-Phenanthroline Derivative: Syntheses, Structure, Physical Properties and Theoretical Calculation

A new Cd（Ⅱ） coordination polymer, [Cd（L）2（H2O）]n（1）, has been hydrothermally synthesized by using 1-（1 H-imidazo[4,5-f][1,10]phenanthrolin-2-yl）naphthalen-2-ol（HL）,(3-（4-（carboxymethoxy）phenyl）acrylic acid and Cd（NO3）·4 H2O. It crystallizes in monoclinic, space group P21/c with a = 19.41（2）, b = 11.078（12）, c = 20.09（2） ?, β = 116.824（17）o, V = 3855（7） ?3, Z = 4, C46H28CdN8O3, Mr = 853.17, Dc = 1.470 g/cm3, F（000） = 1728, μ（Mo Ka） = 0.621 mm-1, R = 0.0338 and wR = 0.0890. 1 shows a one-dimensional（1 D） zigzag chain structure. The neighboring chains are extended into a two-dimensional（2 D） layer structure by π-π interactions between adjacent L ligands. In addition, Natural Bond Orbital（NBO） analysis was performed by the B3LYP/LANL2DZ method in Gaussian 09 Program. The calculation results show the obvious covalent interaction between the coordinated atoms and Cd（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.

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.

Advances in polymer-stabilized Au nano-cluster catalysis : Interplay of theoretical calculations and experiments

Polymer‐stabilized Au nano clusters （NCs） with mean diameters of 2–10 nm exhibit unique catalytic properties. Several studies have shown that the key factors affecting the catalytic activity of poly‐mer‐stabilized Au NCs are control of the Au NC size, appropriate selection of polymers and optimi‐zation of the reaction conditions. This is because polymer‐stabilized Au NCs exhibit a clear size effect in several catalytic reactions, and the catalytic activity differs with the type of polymer used and the reaction conditions. In order to elucidate the reason underlying the catalytic activity of the polymer‐stabilized Au NCs, much attention is being devoted to the interplay of theoretical calcula‐tions and experiments in catalysis by polymer stabilized Au NCs. The present article mainly summa‐rizes our progress in understanding this interplay in polymer‐stabilized Au NC catalysis.

Theoretical investigations on CO oxidation reaction catalyzed by gold nanoparticles

It is crucial to understand the mechanism of low temperature CO oxidation reaction catalyzed by gold nanoparticles so as to find out the origin of the high catalytic reactivity and extend the indus‐trialization applications of nano gold catalysts. In this work, some theoretical works on CO adsorp‐tion, O2 adsorption, atomic oxygen adsorption, formation of surface gold oxide films, reaction mechanisms of CO oxidation involving O2 reaction with CO and O2 dissociation before reacting with CO on gold surfaces and Au/metal oxide were summarized, and the influences of coordination number, charge transfer and relativity of gold on CO oxidation reaction were briefly reviewed. It was found that CO reaction mechanism depended on the systems with or without oxide and the strong relativistic effects might play an important role in CO oxidation reaction on gold catalysts. In particular, the relativistic effects are related to the unique behaviors of CO adsorption, O adsorption, O2 activation on gold surfaces, effects of coordination number and the wide gap between the chem‐ical inertness of bulk gold and high catalytic activity of nano gold. The present work helps us to understand the CO oxidation reaction mechanism on gold catalysts and the influence of relativistic effects on gold catalysis.

Progress of gaseous arsenic removal from flue gas by adsorption:Experimental and theoretical calculations

Because of its high mobility and difficult capture,gaseous arsenic pollution control has become the focus of arsenic pollution control.It mainly exists in the form of highly toxic As_(2)O_(3)in the flue gas.Therefore,removing gaseous As_(2)O_(3)from flue gas is of great practical significance for arsenic pollution control.Stabilizing gaseous As_(2)O_(3)on the surface of adsorbents by physical or chemical adsorption is an effective way to reduce the content of arsenic in the flue gas and alleviate arsenic pollution.Over the past few decades,various adsorbents have been developed to capture gaseous As_(2)O_(3)in the flue gas,and their adsorption mechanisms have been studied in detail.Thus,it is necessary to review the strategies of arsenic removal from flue gas by adsorption,which can inspire further research.Based on summarizing the morphological distribution of gaseous As_(2)O_(3)in the flue gas,this review further summarizes the removal of gaseous As_(2)O_(3)by several adsorbents and the effect of temperature and the main components of the flue gas on arsenic adsorption.In addition,the mechanism of arsenic removal based on adsorption in the flue gas is discussed in depth through theoretical calculations,which is the particular focus of this review.Finally,prospects based on the present research state of arsenic removal by adsorption are proposed to provide ideas for developing effective and stable adsorbents for arsenic removal from flue gas.

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.

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.

Kinetics of hydrogen constrained graphene growth on Cu substrate

Chemical vapor deposition (CVD) has shown great promise for the large-scale production of high-quality graphene films for industrial applications. Atomic-scale theoretical studies can help experiments to deeply understand the graphene growth mechanism, and serve as theoretical guides for further experimental designs. Here, by using density functional theory calculations, ab-initio molecular dynamics simulations, and microkinetic analysis, we systematically investigated the kinetics of hydrogen constrained graphene growth on Cu substrate. The results reveal that the actual hydrogen-rich environment of CVD results in CH as the dominating carbon species and graphene H-terminated edges. CH participated island sp2 nucleation avoids chain cyclization process, thereby improving the nucleation and preventing the formation of non-hexameric ring defects. The graphene growth is not simply C-atomic activity, rather, involves three main processes: CH species attachment at the growth edge, leading to a localized sp3 hybridized carbon at the connecting site;excess H transfer from the sp3 carbon to the newly attached CH;and finally dehydrogenation to achieve the sp2 reconstruction of the newly grown edge. The threshold reaction barriers for the growth of graphene zigzag (ZZ) and armchair (AC) edges were calculated as 2.46 and 2.16 eV, respectively, thus the AC edge grows faster than the ZZ one. Our theory successfully explained why the circumference of a graphene island grown on Cu substrates is generally dominated by ZZ edges, which is a commonly observed phenomenon in experiments. In addition, the growth rate of graphene on Cu substrates is calculated and matches well with existing experimental observations.

Topological Structure-Modulated Collagen Carbon as Two-in-One Energy Storage Configuration toward Ultrahigh Power and Energy Density

Efficient energy storage devices with suitable electrode materials,that integrate high power and high energy,are the crucial requisites of the renewable power source,which have unwrapped new possibilities in the sustainable development of energy and the environment.Herein,a facile collagen microstructure modulation strategy is proposed to construct a nitrogen/oxygen dual-doped hierarchically porous carbon fiber with ultrahigh specific surface area(2788 m^(2)g^(-1))and large pore volume(4.56 cm^(3)g^(-1))via local microfibrous breakage/disassembly of natural structured proteins.Combining operando spectroscopy and density functional theory unveil that the dual-heteroatom doping could effectively regulate the electronic structure of carbon atom framework with enhanced electric conductivity and electronegativity as well as decreased diffusion resistance in favor of rapid pseudocapacitive-dominated Li^(+)-storage(353 mAh g^(-1)at 10 A g^(-1)).Theoretical calculations reveal that the tailored micro-/mesoporous structures favor the rapid charge transfer and ion storage,synergistically realizing high capacity and superior rate performance for NPCF-H cathode(75.0 mAh g^(-1)at 30 A g^(-1)).The assembled device with NPCF-H as both anode and cathode achieves extremely high energy density(200 Wh kg^(-1))with maximum power density(42600 W kg^(-1))and ultralong lifespan(80%capacity retention over 10000 cycles).

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.

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.