Interfacial Binding Energy Research Articles

Ru branched nanostructure on porous carbon nanosheet for superior hydrogen evolution over a wide pH range

Water-electrolytic hydrogen production has attracted extensive attention due to it can fully utilize renewable energy sources and residual secondary energy, while the sluggish kinetics reaction rate seriously hinders the hydrogen evolution reaction (HER) progress. Herein, we reported a novel and simple precipitation-calcination method for the synthesis of Ru branched nanostructures on porous N-doping carbon nanosheets (Ru BCNNs/PNC NNSs) with rough surface and step and edge atoms. The overpotentials for Ru BCNNs/PNC NNSs are 33.4 mV, 81.3 mV, and 99.9 mV in acidic, alkaline, and neutral media, respectively, to achieve the current density of 10 mA cm−2, indicating the superior HER performance over a wide pH range due to the unique rough surfaces and abundant of steps and edges atoms. Meanwhile, the Tafel slopes are 21.7 mV dec−1, 111.1 mV dec−1, and 104.7 mV dec−1 for Ru BCNNs/PNC NNSs in 1.0 M HClO4, 1.0 M KOH, and 1.0 M phosphate buffer solution (PBS, pH=7.0), respectively, much lower than that of commercial Pt/C catalysts with mass loading of 10 % from Macklin Inc. (Pt/C-MK). Furthermore, due to the advantages of the strong interface binding energy between Ru and N-C, the Ru BCNNs/PNC NNSs show outstanding durability for HER not only in mild conditions but also in harsh conditions, outperforming most Ru-based electrocatalysts reported previously.

Spark plasma sintering of boron nitride micron tubes reinforced boron carbide ceramics with excellent mechanical property

AbstractIn this paper, the novel boron nitride micron tubes (BNMTs) were used to reinforce commercial boron carbide (B4C) ceramics prepared via spark plasma sintering technology. The effects of the sintering parameters, sintering temperature, the holding time, and the BNMTs content on the microstructure and mechanical properties of B4C/BNMTs composite ceramics were studied. The results indicated that adding a proper amount of BNMTs could inhibit the grain growth of B4C and improve the fracture toughness of the B4C/BNMTs composite ceramics. The prepared composite ceramic sample with 5 wt% BNMTs at 1850°C, 8 min and 30 MPa displayed the best mechanical properties. The relative density, hardness, fracture toughness, and bending strength of the samples were 99.7% ± .1%, 35.62 ± .43 GPa, 6.23 ± .2 MPa m1/2, and 517 ± 7.8 MPa, respectively. Therein, the corresponding value of hardness, fracture toughness, and bending strength was increased by 10.3%, 43.59%, and 61.5%, respectively, than that of the B4C/BNMTs composite ceramic without BNMTs. It was proved that the high interface binding energy and bridging effect between boron carbide and BNMTs were the toughening principle of BNMTs.

Epitaxial Growth of GaN/AlN on h-BN/Si(111) by Metal–Organic Chemical Vapor Deposition: An Interface Analysis

Among III-nitride semiconductors, hexagonal boron nitride (h-BN) has a two-dimensional crystal structure and can be used as an insulator for nanotransistors or a substrate release layer for flexible electronics, which heavily rely on its interface properties. In this study, h-BN films were successfully grown on 150 mm Si(111) substrates by metal–organic chemical vapor deposition using AlN as a nucleation layer, and van der Waals epitaxy of GaN on the h-BN films was investigated, including the challenges of exfoliation of epilayers. As a result of the accumulated stress in GaN films during growth, self-exfoliation of GaN films was observed on GaN of thickness 1 μm and more. This issue was resolved by decreasing the h-BN thickness from 8 to 3 nm and lower, which results in improved crystal quality as evidenced by the smaller linewidth of the (0002) GaN X-ray rocking curves. Based on the exfoliation behavior of a series of GaN grown with different thicknesses, a self-exfoliation mechanism was proposed and an interface binding energy of 54 meV was estimated for the h-BN/AlN interface.

Modulating the Schottky barriers of metal-2D perovskite junctions through molecular engineering of spacer ligands.

The crucial role of spacer ligands in affecting the contact properties of metal-2D perovskite junctions, which can severely affect device performance, is revealed in this work. We studied the contact properties of Ag, Au, and Pt with 2D perovskites that possess ligands with different sizes and functional groups. It is found that the interface binding energy, Schottky barrier height (SBH), and tunneling property depend strongly on the ligand size and functional group type. Small-size ligands can induce effective interface coupling and result in perturbed perovskite electronic properties and a high tunneling probability. In addition, high work-function metals and more electronegative functional groups can induce more severe band shifts at the interface. The features of diverse ligands ensure a widely tunable SBH ranging from 0-1.07 eV. This study provides guidance for developing more effective 2D perovskite-based electric nanodevices by tuning the contact properties through molecular engineering of spacer ligands.

Diamond/c-BN van der Waals heterostructure with modulated electronic structures

The structural and electronic properties of (100), (110), and (111) diamond/cubic boron nitride (c-BN) heterostructures are systematically investigated by first principles calculation. The interface between diamond and c-BN shows the weak van der Waals interactions, which is confirmed by the interface distance and interface binding energy. The diamond/c-BN structures are the direct bandgap semiconductors with moderate bandgap values ranging from 0.647 eV to 2.948 eV. This work helps to promote the application of diamond in electronic and optoelectronic devices.

Effect of the mesoporous size, structure and surface on the melting and heat transport properties of solar salt

Molecular dynamics simulations combined with experimental methods were used to summarize the changes of thermophysical parameters such as bulk thermal expansion coefficient, thermal conductivity, specific heat capacity at constant pressure and melting point, which based on the radial distribution function and interaction energy. The micro-mechanisms of the melting and heat transport properties of solar salts at the nanoscale were analyzed. The simulation and experimental results show that the bulk thermal expansion coefficient of solar salt decreases with the increase of the mesopore size. At the same scale, the bulk thermal expansion coefficient of the nanopillar solar salt is smaller than that of the spherical structure solar salt in the nanopore. The raising of the scale enhances the thermal conductivity of the solar salt, but has little effect on the specific heat capacity. The thermal conductivity and specific heat capacity of the CPCM are improved with the increase of Al 2 O 3 in the skeleton. The variation of the skeleton structure has a certain influence on the specific heat capacity of CPCM. The melting point of solar salt shows a trend of increasing and then decreasing with the raising of nanopore size. The change of the mesoporous structure affects the melting point of CPCM. The addition of the porous alumino silicate ceramic skeleton reduces the melting point of the solar salt. And the melting point of the CPCM with larger interfacial binding energy is relatively higher. • Correspondence between microscopic simulation and macroscopic thermal analysis data. • Micro analysis of scale effect on melting and heat transport proportions of CPCMs. • Micro analysis of structure effect on the melting and heat transport proportions of CPCMs. • Micro analysis of surface effect on the melting and heat transport proportions of CPCMs.

Improvement of the performance of graphene/Al(1 1 1) interface with defect mode and doped mode

We investigated the effects of vacancy defect and heteroatom doped (B, N, and Si) on the properties of the graphene/Al (111) interface by using density functional theory. The results show that the interface binding energy can be changed by vacancy defect and heteroatom doped. B-doped can reduce the interface interlayer distance. It is found that the defect or heteroatom doped can improve the charge transport and orbital hybridization ability in the interface. It shows that the bonding strength of the graphene/Al interface can be controlled by graphene modification, which can improve the performance of the graphene/Al interface for optoelectronic devices.

Investigation of the interface electronic characteristics of β-Ga2O3 (1 0 0)/4H-SiC (0 0 0 1)

Due to lower thermal conductivity of β-Ga2O3, gallium oxide power device based on high thermal conductivity substrates has received extensive attention. As a high thermal conductivity semiconductor material, 4H-SiC is suitable as a substrate to combine with β-Ga2O3 due to its small lattice mismatches. Herein, first principle is utilized to analyze the interfacial geometry structures, formation energy, interface binding energy and the electronic properties of the bonding mechanism at different β-Ga2O3 (100)/4H-SiC (0001) interfacial models. The interface formation energy and interface binding energy of β-Ga2O3 (100)/4H-SiC (0001) heterointerfaces are studied by using first principles. The results show that six different β-Ga2O3 (100)/4H-SiC (0001) heterostructures can be stable. Among the six interface models, Si-O interface possesses the smallest values of interface formation energy and interface binding energy after geometry relaxation, indicating highest thermodynamic stability. The differential charge density, bader charge, electron local function and partial density of states (PDOS) of β-Ga2O3 (100)/4H-SiC (0001) interface models are comprehensively investigated to understand the interfacial bonding strength and stability. It is shown that electrons are mainly transferred from the 4H-SiC side to the β-Ga2O3 side. Compared to other interface models, Si-O models, Si-GaO models can form strong Si-O chemical bond at the interface, while the interaction between the C-O models and C-GaO models forms a C-O bond with covalent bond properties.

Local lattice structures and electronic properties of β-Li3PS4/CuS interface

In all-solid-state lithium–sulfur batteries (ASSLBs), unfavorable solid–solid contact at the interfaces with sulfide electrolyte (SE) is one of the important reasons affecting the properties of ASSLBs. CuS is a promising cathode material, and [Formula: see text]-Li3PS4 (LPS) is a newly found SE used for ASSLBs. In order to deeply explore the electronic properties at the interface between these two materials, we used the first-principles calculation method to investigate the local lattice structures, electronic properties, work-function, and charge distribution of LPS/CuS interface. The interface binding energy of the LPS/CuS interface is about −0.568 J/m2. Hence, the LPS/CuS interface structure is thermodynamically reasonable and stable with newly formed chemical bonds at the interface. The interfacial electron density of state shows the metallic properties, which are mainly contributed by Cu-[Formula: see text], [Formula: see text] orbitals and S-[Formula: see text], [Formula: see text] orbitals in CuS and S-[Formula: see text] orbital electrons in LPS. Furthermore, the work function of the interface means the formation of a space charge layer, which has a certain influence on the charge and discharging process.

Deterioration of FRP/RPUF interfacial bond strength under moisture intrusion: An analysis from the perspective of adsorption

Fiber-reinforced polymer (FRP) / rigid polyurethane foam (RPUF) interface is a typical bonding interface composed of two layers of material. Adsorption theory is widely used in the analysis of such interfacial bonding. The mechanism of influence of water on the interfacial bonding strength of FRP/RPUF was discussed from the perspective of adsorption effect. Water intrusion experiments of FRP/RPUF interface samples were conducted at 98 °C for 672 h. The change characteristics of interfacial mechanical properties were obtained by compression-shear test, and the change characteristics of active groups were obtained by X-ray photoelectron spectroscopy (XPS) analysis. Based on the XPS results, the functional groups between interfaces were directionally regulated, and the contribution of active groups to surface free energy was evaluated. A molecular dynamics simulation method was used to simulate the process of water intrusion into the interface. Experiments and simulations show that water intrusion will cause a significant decrease in the macroscopic mechanical properties of the interface. The chemical adsorption caused by active functional groups of oxygen and nitrogen has little effect on the interface bonding strength and decreases with the water intrusion. Interface bonding mainly depends on the physical adsorption caused by non-bonded interaction. The simulation results show that the hydrogen bond energy makes a significant contribution to the interface binding energy. The invasion of water molecules will recombine the original hydrogen bonds of the interface system, resulting in the decrease of the stability of the interface structure.

Enhanced Aramid/Al2O3 interfacial properties by PDDA modification for the preparation of composite insulating paper

To further improve the electrical insulation properties of meta-aramid paper, polydimethyldiallyl ammonium chloride (PDDA) was used for the modification of nano-Al2O3 in this work. The modified products were characterized by means of transmission electron microscopy, Fourier transform infrared spectrometer and liquid Zeta potential. The original and PDDA-modified nano-Al2O3 was doped into the aramid fiber composite, and the effects of PDDA and filler mass fraction on several properties such as electrical conductivity, breakdown strength and surface charge dissipation rate of insulating paper were studied. Finally, the interfacial properties of the composites were investigated using molecular dynamics. The results showed that PDDA was successfully coated on the surface of nano-Al2O3, and its surface potential was changed from negative to positive, which could improve the interface characteristics between filler and matrix and enhance the dielectric strength of aramid paper. Besides, saturation effect of PDDA modification was observed, and when the amount of PDDA was 10% and the content of modified nano-Al2O3 was 3%, the breakdown strength of aramid paper was increased by 20%, and the volume conductivity was decreased by 68%. The simulation result revealed that PDDA could improve the insulation performance of aramid paper by reducing the interfacial binding energy between aramid and filler.

First-Principles Study on the Adsorption Characteristics of Corrosive Species on Passive Film TiO2 in a NaCl Solution Containing H2S and CO2

The adsorption characteristics of corrosive anions (Cl−, HS−, S2−, HCO3− and CO32−) on TiO2 of TC4 titanium alloy in a NaCl solution containing H2S and CO2 were studied by density functional theory (DFT). The stable adsorption configuration of each corrosive species on the TiO2 (110) surface was obtained by geometric optimization, and the electronic structure and interface binding energy were calculated and analyzed. The results showed that the optimal adsorption positions of Cl−, HS−, S2−, HCO3− and CO32− on TiO2 (110) were all bridge positions. There was a strong charge interaction between the negatively charged Cl, S and O atoms in Cl−, HS−, S2−, HCO3− and CO32− and the positively charged Ti atoms of TiO2. The interface bonding was mainly caused by charge movement from around Ti atoms to around Cl, O, S atoms. The energy levels were mainly caused by the electron orbital hybridization of Cl-3p5, S-3p4, O-2p4 and Ti-3d2. All adsorption configurations were chemical adsorption. The order of influence of the five ions on the stability of TiO2 was S2− > CO32− > Cl− > HS− > HCO3−. Finally, a novel corrosion mechanism was proposed to illustrate the dynamic evolution processes of pits.

Thermal conductivities of Ti3C2Tx MXenes and their interfacial thermal performance in MXene/epoxy composites – a molecular dynamics simulation

Ti-based MXene has been widely investigated for its excellent electronic properties but the thermal performance of Ti3C2Tx still remains uncharted on the molecular scale, which could significantly affect the thermal conductivity of their composites. This work adopted molecular dynamics method and effective medium theory (EMT) to analyze the thermal conductivity of 4 types of MXenes, including Ti3C2, Ti3C2F2, Ti3C2O2 and Ti3C2(OH)2, as well as their epoxy composites. The results showed that the terminal groups could reduce the phonon scattering in MXenes which could increase the thermal conductivity and also the interfacial affinity between MXene and epoxy molecules by improving interfacial binding energy. The Ti3C2O2 has the highest thermal conductivity of 140.25 Wm−1K−1, while Ti3C2(OH)2 has the lowest interfacial thermal resistance, which could lead a higher thermal conductivity in composite when its flake was under the critical size. The EMT results showed that Ti3C2O2 could significantly improve the TC of epoxy under a lower filler content; and the MD simulation parameters were validated by the comparison between other works and EMT prediction in this work. The current study provides suggestions for selecting Ti3C2Tx as fillers in composites that need fast heat dissipation.

Electron transport at TiO2/perovskite interfaces by considering the defect effects: a first-principles insight

The interface property of perovskite solar cells (PSCs) is very important, which can influence the electron transmission efficiency and stability of the cells. In this text, we have discussed the stability and bonding characteristics of PbI2/TiO2 interfaces by using the first-principles method. The PbI2/TiO2 interfaces have a high interfacial binding energy of -0.93 J/m2, where the Ti-I and Pb-O bonds could form. Furthermore, the electron transport at the interfaces has been analyzed by the partial density of states by comparing the clean interfaces and interfaces with different defects. The results show that the clean PbI2/TiO2 interfaces could cause a stronger internal electric field, which might make the electron-hole pairs separate more easily at the interfaces. Also, it is found that common defects VI and Ii are relatively easy to form at the interfaces. Some defects at low concentrations might have little effect on the electron transport at the interfaces, while they are harmful only when the concentration increases. However, VPb with a high formation energy could adversely affect the electron transmission even at low concentrations. Controlling the defects at the interfaces is essential to improve the power conversion efficiencies (PCEs) and stability of PSCs.

Dynamic Reconfiguration of Compressed 2D Nanoparticle Monolayers.

A Gibbs monolayer of jammed, or nearly jammed, spherical nanoparticles was imaged at a liquid surface in real time by in-situ scanning electron microscopy performed at the single-particle level. At nanoparticle areal fractions above that for the onset of two-dimensional crystallization, structural reorganizations of the mobile polymer-coated particles were visualized after a stepwise areal compression. When the compression was small, slow shearing near dislocations and reconfigured nanoparticle bonding were observed at crystal grain boundaries. At larger scales, domains grew as they rotated into registry by correlated but highly intermittent motions. Simultaneously, the areal density in the middle of the monolayer increased. When the compression was large, the jammed monolayers exhibited out-of-plane deformations such as wrinkles and bumps. Due to their large interfacial binding energy, few (if any) of the two-dimensionally mobile nanoparticles returned to the liquid subphase. Compressed long enough (several hours or more), monolayers transformed into solid nanoparticle films, as evidenced by their cracking and localized rupturing upon subsequent areal expansion. These observations provide mechanistic insights into the dynamics of a simple model system that undergoes jamming/unjamming in response to mechanical stress.

Mechanical Properties of Amide Functionalized CNT/NBR at Different Temperatures: A Molecular Dynamics Study.

A comprehensive study on the mechanical properties of a pure carbon nanotube (PCNT)/nitrile butadiene rubber (NBR) composite and an amide-functionalized carbon nanotube (CONH2–CNT)/nitrile butadiene rubber (NBR) composite was carried out using molecular dynamics (MDs) simulations at different temperatures. The effects of temperature on the mechanical properties, fractional free volume (FFV), MSD, dipole autocorrelation function, number of hydrogen bonds of PCNT composites, and functionalized CNT composites were analyzed and compared, and the pull-out behavior of the composites under different condition temperatures was simulated. The enhancement mechanism of the interface interaction between the functionalized carbon nanotubes and the NBR matrix was explained from an atomic point of view. The results show that, due to the existence of hydrogen bonds, higher interfacial binding energies were formed between PCNT and NBR, and FFVs and MSDs were restricted at each temperature, with the mechanical properties of the composites being improved by 5.02–25.93%.

Molecular Simulation Study on Mechanical Properties of Microcapsule-Based Self-Healing Cementitious Materials.

Microcapsule-based self-healing concrete can effectively repair micro-cracks in concrete and improve the strength and durability of concrete structures. In this paper, in order to study the effect of epoxy resin on the cement matrix at a microscopic level, molecular dynamics were used to simulate the mechanical and interfacial properties of microcapsule-based self-healing concrete in which uniaxial tension was carried out along the z-axis. The radial distribution function, interface binding energy, and hydrogen bonding of the composite were investigated. The results show that the epoxy resin/C-S-H composite has the maximum stress strength when TEPA is used as the curing agent. Furthermore, the interface binding energy between epoxy resin and cement matrix increases with increasing strain before the stress reaches its peak value. The cured epoxy resin can enhance both the interfacial adhesion and the ductility of the composite, which can meet the needs of crack repair of microcapsule-based self-healing cementitious materials.

Tearing behavior induced by van der Waals force at heterogeneous interface during two-dimensional MoS<sub>2</sub> nanoindentation

Combining with <i>in situ</i> nanomechanical testing system and video module of scanning electron microscope, the nanoindentation testing is performed to study the peeling-tearing behavior of two-dimensional material van der Waals heterostructures. After two-dimensional MoS<sub>2</sub> nanosheets prepared by chemical vapor deposition are assembled into MoS<sub>2</sub>/SiO<sub>2</sub> heterostructures by wet transfer, the nanoindentation is carried out by manipulating the tungsten probe in the<i> in situ</i> nanomechanical testing system. When the tungsten probe is tightly indenting into MoS<sub>2</sub> nanosheets, a new W/MoS<sub>2</sub>/SiO<sub>2</sub> heterostructure is assembled. With the tungsten probe retracting, the adhesive effect makes the two-dimensional MoS<sub>2</sub> nanosheet peel off from SiO<sub>2</sub>/Si substrate to form a bulge. After reaching a certain height, under the van der Waals adhesion interaction, an incomplete penetration fracture occurs along the arc line contacting the needle. Then cleavage appears and produces two strip cracks and MoS<sub>2</sub>/SiO<sub>2</sub> interface separation takes place simultaneously, before a large area of MoS<sub>2</sub> nanosheet is teared. Based on the density functional theory calculation of interface binding energy density of van der Waals heterogeneous interface, the interface binding energy density of MoS<sub>2</sub>/W is verified to be larger than that of MoS<sub>2</sub>/SiO<sub>2</sub>, which explains the adhesion peeling behavior of MoS<sub>2</sub> induced by van der Waals force between heterogeneous interfaces, perfectly. By using the peeling height and tearing length of MoS<sub>2</sub> recorded by video module, the fracture strength of MoS<sub>2</sub> is obtained to be 27.055 GPa and stress-strain relation can be achieved according to the film tearing model. The density functional theory simulation results show that the fracture strength of MoS<sub>2</sub> is in a range of 21.7–32.5 GPa, and the stress-strain relation is consistent with the experimental result measured based on film tearing model. The present work is expected to play an important role in measuring the fracture strengths of two-dimensional materials, the assembly, disassembly manipulation and reliability design of two-dimensional materials and van der Waals heterostructures devices.

Effect of temperature and water penetration on the interfacial bond between epoxy resin and glass fiber: A molecular dynamics study

According to the hydrothermal working environment, accidents related to composite insulator string rupture are frequently encountered in transmission line, which cause serious hazard to the stability of power system. The interface between epoxy resin matrix and glass fiber fillers is one of the microscopic interfaces in the insulator core rod. The adhesion strength of that interface has important implications for the overall mechanical properties of the core rod. This study aims to analyze the influence of temperature and water intrusion on the interfacial adhesions. By molecular dynamics (MD) simulation, a molecular modelling of epoxy resin / glass fiber interface under water molecular environment was established. The mechanism of deterioration is indicated through the interfacial binding energy, ester number, radial distribution function (RDF) and H-bonds number of the interface model. It was found that when the temperature increased to a certain level, the water molecules were easy to migrate to the interface through the holes in the epoxy resin. When the temperature reaches 373 K, the epoxy resin occurs hydrolysis reaction, which will promote the cracking of epoxy resin. Meanwhile, water molecules migrated to the interface can hinder the formation of hydrogen bonds between epoxy resin and glass fiber. Under the synergistic effect of the above factors, water gradually causes the degradation of epoxy resin / glass fiber interface.

Compound Cleaning Agent for Oily Sludge from Experiments and Molecular Simulations.

This paper reported a new oily sludge compound cleaning agent formula, which used a combination of molecular simulation and experimental methods to study its interfacial formation energy (IFE), and exciting results were obtained. From a total of 24 surfactants in five categories, sodium silicate (Na2SiO3), sodium dodecylbenzene sulfonate, and fatty alcohol polyoxyethylene polyoxypropylene ether (JFC-SF) were screened out because of their excellent washing oil effect. Under a reasonable orthogonal system, when the mass ratio of the three surfactants was 3:1:1, the oil desorption effect was the best, the oil residual rate could reach 2.13%, and the oil removal efficiency could reach 93.53%. Verified by the molecular dynamics simulation module, the absolute value of the interface binding energy was the largest at this compound ratio, which was 465.71 kcal/mol. More importantly, we have discussed in depth the mechanism of adsorption and permeation of oily sludge by cleaning agents. Through single-factor influence experiments, the following optimized working condition parameters of the cleaning agent were determined: cleaning conditions with an agent content of 4%, a temperature of 70 °C, a stirring speed of 400 rpm, a cleaning time of 30 min, and a liquid–solid ratio (L/S) of 4:1. The research results laid the foundation for resource utilization, harmlessness, and reduction of oily sludge in the Liaohe oilfield.