Density Functional Theory Molecular Dynamics Research Articles

Size-matched hierarchical porous carbon materials anchoring single-atom Fe-N4 sites for PMS activation: An in-depth study of key active species and catalytic mechanisms

Single-atom catalysts are considered to be one of the most promising catalysts for AOPs. However, how to design and synthesize cost-effective and highly loaded single-atom catalysts is the bottleneck limiting its development and application. In this study, we report a highly loaded single-atom iron catalyst (Fe-SAC-BC) using waste biomass as a carbon carrier to anchor Fe-N4 sites. The catalyst showed excellent catalytic performance and stability in wastewater treatment. Unlike conventional radical oxidation, the non-radical degradation process of Fe-N4 as the active site and high-valent iron-oxygen intermediates as the key active species identified by burst and probe experiments. DFT calculations and molecular dynamics simulations were applied to the catalytic mechanism of Fe-SAC-BC, in which Fe (III)-N4 is the most likely active site and Fe (IV)-OH is the most dominant active species. This study provides new strategies and understanding for the design of novel single-atom catalysts and the mechanistic probing of the non-radical pathways of AOPs.

Atomic-level insights from density functional theory and ab initio molecular dynamics calculations for oxidation mechanism of transition metal doping Nb4AlC3 (0 0 0 1) surface

Poor oxidation resistance limits the further application of Nb4AlC3 MAX phase, a high-temperature structural candidate material. Transition metal doping can significantly address this problem. In this paper, we investigated the oxidation mechanism of the Nb4AlC3 (0 0 0 1) surface with Ti doping by combining density functional theory (DFT) and ab initio molecular dynamics (AIMD). DFT results indicate that the Nb surface has a lower surface energy, making it more easily exposed and reactive towards O2 molecules. O atoms are expected to preferentially occupy the HCP and FCC hollow sites on the surface. The Ti-doped surface has a stronger adsorption capacity for O atoms. O atoms gain electrons, while Nb/Ti atoms lose electrons. The formation of O–Nb/Ti bonds is facilitated by the hybridization of O-p and Nb/Ti-d orbitals. And O–Ti bonds are more stable than O–Nb bonds. AIMD simulation results show that O2 molecules on the clean and doped surfaces gradually dissociate into O atoms over time. These O atoms then combine with surface atoms to form Nb oxides, Ti oxides, and Nb–Ti oxides. With the passage of time, the concentration of Ti oxides increases while that of Nb oxides decreases. And the oxidation rate at 1073K is higher. The O–Nb/Ti bond population gradually increases over time, indicating that the bonding between O atoms and the surface is slowly strengthened. This study provides fundamental insights into the oxidation mechanism of transition metal-doped 413 MAX phase Nb4AlC3 surfaces.

Adsorption of Multi-Collector on Long-Flame Coal Surface via Density Functional Theory Calculation and Molecular Dynamics Simulation

The quantum chemical properties of long-flame coal (LFC) and collectors (kerosene, diesel, diethyl phthalate (DEP), biodiesel collector (BDC), and emulsified biodiesel collector (EBDC)) were analyzed via the density functional theory (DFT). The molecular dynamics (MD) of the coal–collector–water system and the adsorption of collectors on LFC were conducted based on the first principles. The results showed that the frontier molecular orbitals of kerosene, diesel, DEP, and BDC were 0.38 eV, 0.28 eV, 0.27 eV, and 0.20 eV, respectively. The chemical reactivity order of the above mentioned collectors was BDC > DEP > diesel > kerosene. Kerosene, diesel, and DEP adsorbed with carbonyl, hydroxyl, and carboxyl groups in LFC, respectively. Carboxyl groups in BDC and carboxyl groups in LFC bilaterally adsorbed, while BDC repelled water molecules via hydrogen bonds on the LFC surface. In the systems of BDC and EBDC, the diffusion coefficients of a water molecule were 2.83 × 10−4 cm2/s and 3.73 × 10−4 cm2/s. The emulsifier that adsorbed onto the oil–water interface of the coal–BDC–water system improved the dispersion of BDC during flotation, while at the same time increasing the number of hydrogen bonds between BDC and LFC, which accelerated the migration of water molecules from the LFC surface.

Barium isotope fractionation during granitic magmatism and potential of δ138/134Ba for distinguishing magmatic-hydrothermal transition in granitic magma systems

The geochemistry of Ba is commonly used to study igneous processes and fluid-melt interaction in subduction zone and granitic environments. Recent advances in analytical techniques have also indicated that Ba isotope geochemistry has the potential to significantly augment these studies. Understanding the Ba isotope fractionation mechanisms is thus critical if this potential is to be fully realized. Hence, we have used the first-principles calculations based on the density functional theory (DFT) and long-time ab initio molecular dynamics (AIMD) simulation to calculate Ba isotope fractionation during felsic magma evolution. In fluids, the reduced partition function ratio (β factor) of aqueous Ba2+ is highly variable, depending on the coordination number (n) of H2O in the first hydration shell. At ambient surface conditions on the Earth, n = 8 best represents the aqueous Ba2+ species in natural fluid, and the temperature-dependent equilibrium Ba isotope fractionation between barite/witherite and fluids can be described by the relationships: 103lnαwitherite-fluid = −0.00009×(106/T2)2 + 0.0603×(106/T2) + 0.0003 and 103lnαbarite-fluid = −0.0001×(106/T2)2 + 0.0648×(106/T2) + 0.0004, which is consistent with previous theoretical and experimental studies. In hydrothermal fluids, the hydration number of Ba2+ varies from 4 to 6 at high P-T, and the cumulative average of 103lnβ is derived to be 0.0798 ± 0.005‰ in 923.15 K and 0.2 GPa. In silicate minerals, the enrichment of heavy Ba isotopes decreases in the sequence of muscovite > microcline ≈ celsian ≈ sanbornite > barylite > phlogopite. Variations in Ba concentrations and the degree of Al-Si disordering only induce limited Ba isotope fractionation, which would be hard to distinguish analytically. At high temperatures (> 600 °C), the melt phase is enriched in heavy Ba isotopes relative to any coexisting aqueous fluid and crystallizing minerals. During the early stages of felsic magma differentiation involving plagioclase crystallization as the main mineral, the δ138/134Ba and concentration in the residual melt remain close to their initial values, but any fluid exsolved from the melt will have light δ138/134Ba values. The high Ba distribution coefficient of K-feldspar means that the resultant K-feldspar granite inherits > 90% of the Ba contained in the initial magma reservoir. Hence, the δ138/134Ba of K-feldspar is close to that of the initial melt. During the final stage of felsic magma evolution, mixing of exsolved fluids from deeper reservoirs may significantly reduce the δ138/134Ba of the now Ba-depleted melt, and can account for the low δ138/134Ba values measured in highly differentiated leucogranites and pegmatites.

Insight into the effect of functional groups on the inhibition performance for imidazoline: DFT and MD simulations

The imidazoline corrosion inhibitors have been a hot topic in research. The corrosion inhibition performance of imidazoline modified by different functional groups is probed in this study. The quantum chemical parameters for predicting the inhibition performance and adsorption behaviours of modified imidazoline are investigated by density functional theory calculation and molecular dynamics simulation. By evaluating the effect of functional groups on imidazoline corrosion inhibition, the modified imidazoline with better corrosion inhibition performance is screened. Besides, the interactions between modified imidazoline and the Fe(100) surface are explored. The results verify that Imidazoline-CO-CH3 and Imidazoline-CHO have the best corrosion inhibition performance. This work will not only facilitate the design and synthesis of imidazoline corrosion inhibitors with improved corrosion inhibition performance, but also provide guidance for large-scale synthesis of high-efficiency corrosion inhibitors in industry.

Probing pH-Dependent Dehydration Dynamics of Mg and Ca Cations in Aqueous Solutions with Multi-Level Quantum Mechanics/Molecular Dynamics Simulations.

The dehydration of aqueous calcium and magnesium cations is the most fundamental process controlling their reactivity in chemical and biological phenomena, such as the formation of ionic solids or passing through ion channels. It holds particular relevance in light of recent advancements in the development of carbon capture techniques that rely on mineralization for long-term carbon storage. Specifically, dehydration of Ca2+ and Mg2+ is a key step in proposed carbon capture processes aiming to exploit the relatively high concentration of dissolved carbon dioxide in seawater via the formation of carbonate minerals from solvated Ca2+ and Mg2+ cations for sequestration and storage. Nevertheless, atomic-scale understanding of the dehydration of aqueous Ca2+ and Mg2+ cations remains limited. Here, we utilize rare event sampling via density functional theory molecular dynamics and embedded wavefunction theory calculations to elucidate the dehydration dynamics of aqueous Ca2+ and Mg2+. Emphasis is placed on the investigation of the effect pH has on the stability of the different coordination environments. Our results reveal significant differences in the dehydration dynamics of the two cations and provide insight into how they may be modulated by pH changes.

Constructing Efficient Mg(CF3SO3)2 Electrolyte via Tailoring Solvation and Interface Chemistry for High‐Performance Rechargeable Magnesium Batteries

AbstractNon‐passivating and chlorine‐free electrolytes are crucial for making rechargeable magnesium batteries practically feasible. Rational design of a brand‐new electrolyte should balance both Mg salt and solvent considering that the interfacial reactions occurring at electrolyte/electrode interface involve with ion solvation structure. Herein, nitrogenous 2‐methoxyethylamine (MOEA) is employed as co‐solvent to regulate the coordination behavior of cations/anions in Mg(CF3SO3)2‐G2 electrolyte after a series of screenings, which enables significantly ameliorated physiochemical properties. In‐depth insight on the mechanism of MOEA participating in the solvation structure formation and interfacial reactions is deduced via density functional theory calculations and molecular dynamics simulations. The decompositions of MOEA‐tailored cationic/anionic complexes shield Mg anode and Mo6S8 cathode with Mg3N2 and CxNy‐rich layers, respectively, which enable to suppress side reaction and accelerate Mg2+ transportation with competing desolvation at the interfacial layer. All the merits endow remarkable performances of symmetric/asymmetric cells with ultralong‐cycle lives over 5000 h and a remarkable average Coulombic efficiency of 98.3% after 8200 cycles (≈11 months), respectively. Additionally, a cheerful discharge capacity of ≈59.3 mAh g−1 is obtained over 1000 cycles at 0.5 C in Mo6S8||Mg full cell.

Mechanistic Basis for Oxoammonium Salt‐Mediated Tertiary Alcohol Oxidative Transformation Decoded by Computations and Experiments

AbstractOxoammonium salts have demonstrated superior efficacy as reagents in mediating various reactions involving tertiary alcohols, including the eliminative functionalization of tertiary benzylic alcohols, oxidative rearrangement of tertiary allylic alcohols, and oxidative Nazarov cyclization. These reactions have been believed to be triggered by the addition of alcohols to the N−O double bonds of oxoammonium cations. However, in this work, a combination of density functional theory (DFT) and ab initio molecular dynamics (AIMD) calculations shows that the formation of this adduct is thermodynamically unfavorable. A thorough exploration of the possible mechanisms has shown that the reaction occurs through the ring opening of the oxoammonium cation. The oxoammonium cation acted as a masked tertiary carbocation and triggered the subsequent reactions. The computational results were further supported by control experiments and high‐resolution mass spectroscopy (HRMS) characterization.

The base versus tip growth mode of carbon nanotubes by catalytic hydrocarbon cracking: Review, challenges and opportunities

Hydrogen gas production using catalytic hydrocarbon cracking on metal nanoparticles has become a vital bridge technology, as this process, unlike the traditional methane-based reforming process, does not co-produce carbon gasses (e.g., CO, CO2). The major benefit of direct catalytic methane cracking using a nanostructured catalyst is the formation of solid carbon in high-value products, such as carbon nanotubes (CNTs) or filaments. This solid carbon can then be removed physically and valorized. However, it is challenging to design a catalyst capable of sustaining its activity after solid carbon has started to deposit and grow, meanwhile preventing the formation of coke. For CNTs, in particular, the base growth mode of CNTs is the desired pathway, as the catalyst can then be regenerated and re-used. If the CNTs are formed under the tip-growth mode, the catalyst particle will be lifted off the support of the regeneration and reusability is lost. Therefore, the study of CNTs growth modes is a vital topic, both experimentally and theoretically, of designing appropriate catalysts. To date, enormous efforts have been made to investigate conditions where the CNTs base growth mode can be maintained during the carbon deposition process. Several possible correlations and mechanisms regarding the base growth mode have been explored and established. Theoretical calculations and numerical simulations across length scales were conducted to investigate the nucleation mechanism and growth of CNTs. Density functional theory (DFT), classical and quantum-based molecular dynamics (MD) and Monte Carlo (MC) simulations were also carried out to study the initial CNT cap formation and its encapsulation during the catalytic hydrocarbon cracking process. A thermodynamics-based nucleation formula of CNTs for both the base and tip growth modes was also established. However, there is still no consensus on what determines the CNT growth modes and what the roles are of the various influencing factors such as the nanoparticle size, the oxidation state of the catalyst, the mechanical properties of CNT, and the catalyst-support interaction. This paper reviews the current status of CNT's growth mechanism development. The benefits and limitations of theory and modeling approaches concerning CNT growth modes are discussed.

A computational investigation on the roles of binding affinity and pore size on CO2/N2 overall adsorption process performance of MOFs through modifying MIL-101 structure

To develop an appropriate metal-organic framework to capture CO2 from dry flue gas, understanding the roles of structural modifications, location of primary adsorption sites and underlying adsorption mechanisms is crucial. Herein, effects of type, position and concentration of nitrogen-containing functional groups and C/N-substituted ligands are investigated on overall CO2/N2 adsorption process performance and mechanism of pristine and metal-substituted MIL-101 MOFs. In this investigation, density functional theory computations, grand-canonical Monte-Carlo, and molecular dynamics simulations are applied. Taguchi-based overall evaluation criteria objective function is also used to assess the overall adsorption performances of these MIL-101 MOFs in terms of CO2 uptake capacity, CO2/N2 selectivity, isosteric heat of adsorption and mass transfer resistance. The PBE/DZVP computations resulted in the CO2-framework binding energies ranging from −3.85 to −21.01 kJ/mol implying an acid-base type of physisorption. A correlation is introduced to estimate the CO2 uptake capacity from binding affinity and pore diameter of these MIL-101 MOFs. Mechanistic investigations show that to enhance CO2 uptake capacity and CO2/N2 selectivity, functionalization of the linker ligands is more successful than functionalization of the open metal sites having strong interactions with CO2 molecules. Results also showed that the best possible scenario to improve the overall adsorption process performance of MIL-101 is to substitute the C atom(s) of the BDC ligands with the N atom(s), regardless of the central metal atom type. The comprehensive molecular design approach introduced in this work can be used as a methodology by scientists for the development of new MOFs for practical CO2 capture applications.

Surface Interaction Effect and Mechanism of Methionine Derivatives as Novel Inhibitors for Alkaline Copper CMP: Insights from Molecular Simulation and Experimental Analysis

To prevent excessive corrosion caused by the slurry in the copper (Cu) chemical mechanical polishing (CMP) process, a corrosion inhibitor is normally required. In this study, the methionine (Met) derivative FMOC-L-Methionine (Fmoc-Met-OH) was explored as a corrosion inhibitor for Cu film CMP in weak alkaline conditions (pH = 8.5). A comprehensive evaluation was conducted to confirm the efficiency of Fmoc-Met-OH as a corrosion inhibitor, combining experiments and theoretical calculations. The results showed that Fmoc-Met-OH could effectively inhibit the corrosion of Cu, with a high inhibition efficiency (IE) of 78.26% while maintaining a high removal rate (RR) of 5703 Å min−1, a low static etch rate (SER) of 676 Å min−1, and a low surface root mean square deviation (Sq) of 1.41 nm. Simultaneously, the results of X-ray photoelectron spectroscopy (XPS) tests and electrochemical analysis confirm that Fmoc-Met-OH molecules can form a dense and ordered adsorption film on the Cu surface. According to the density functional theory (DFT) calculations and molecular dynamics (MD) simulation, it was verified that Fmoc-Met-OH exhibited strong chemical adsorption on Cu substrates, as evidenced by the high binding energy (E Binding) value, low energy gap (ΔE), and radial distribution function (RDF) analysis. The findings provided theoretical evidence of the better inhibition effectiveness of Fmoc-Met-OH at a molecular or atomic level.

Ultrafast Laser Pulse Induced Transient Ferrimagnetic State and Spin Relaxation Dynamics in Two-Dimensional Antiferromagnets.

We employ real-time time-dependent density functional theory (rt-TDDFT) and ab initio nonadiabatic molecular dynamics (NAMD) to systematically investigate the ultrafast laser pulses induced spin transfer and relaxation dynamics of two-dimensional (2D) antiferromagnetic-ferromagnetic (AFM/FM) MnPS3/MnSe2 van der Waals heterostructures. We demonstrate that laser pulses can induce a ferrimagnetic (FiM) state in the AFM MnPS3 layer within tens of femtoseconds and maintain it for subpicosecond time scale before reverting to the AFM state. We identify the mechanism in which the asymmetric optical intersite spin transfer (OISTR) effect occurring within the sublattices of the AFM and FM layers drives the interlayer spin-selective charge transfer, leading to the transition from AFM to FiM state. Furthermore, the unequal electron-phonon coupling of spin-up and spin-down channels of AFM spin sublattice causes an inequivalent spin relaxation, in turn extending the time scale of the FiM state. These findings are essential for designing novel optical-driven ultrafast 2D magnetic switches.

(Invited) Modeling of the Bulk and Electrical Double-Layer Structures of Localized High-Concentration Electrolytes

A new class of electrolytes, localized high-concentration electrolytes (LHCE), have shown many benefits to high-capacity electrodes (lithium (Li)-metal, silicon, sodium, zinc, and potassium).[1] These electrolytes combine high-concentration electrolytes (HCE) with salt and solvent with low-viscosity diluents. The dilutes were added to increase ionic conductivity while the locally highly concentrated salt-solvent clusters will facilitate stable solid-electrolyte interphase (SEI) formation while preventing metallic-dendrite formation. For example, it was demonstrated that an LHCE based on lithium bis(fluorosulfonyl)imide (LiFSI) salt, Dimethoxyethane (DME) solvent, and tris(2,2,2-trifluoroethyl)orthoformate (TFEO) diluent (e.g., LiFSI-1.2DME-2TFEO by mol) forms inorganic-rich, monolithic SEI and shows excellent cycling performance for Li-metal batteries under practical conditions.[2] Here, the interactions among cations, anions, solvent molecules, and diluent molecules create a complex design space, making the trial-and-error empirical approach less efficient.Using density functional theory and classical molecular dynamics simulations, we reveal several important design principles:a) The dielectric constant of the pure solvent or diluent is not a good descriptor to describe the solubility of the salt in solvent and diluent.b) The single ion–solvent (diluent) binding energy is insufficient to predict the solubility, which also depends on the molecular structures and the corresponding solvation shell structure.c) The salt-solvent, salt-diluent, and diluent-solvent solubilities jointly determine the solvation structures in LHCE. For example, at certain concentrations, the Li+ solvation shells contain both anions and solvent molecules with minimal participation of the diluent molecules. The local salt concentration can be even higher than its counterpart in the HCE. These simulated solvation structures in bulk electrolytes compare well with Raman spectrum and SAXS data.d) Moreover, the solvation structures are temperature-sensitive. We revealed why the local salt concentration is higher at a certain temperature by MD simulations, which is further validated through Raman deconvolution analyses.e) The SEI formation is sensitive to the electrolyte structure near a charged surface. Therefore, the electrical double-layer (EDL) structure of LHCE needs to be resolved. Here we give a statistical representation of the LHCE in the EDL and show how it differs from the bulk structure and its impact on SEI formation.Reference:[1] J. Electrochem. Soc., 2021, 168, 010522[2] Nat. Energy 2019, 4, 796-805

Supramolecular Assemblies of Melamine-2-Thiobarbiturate and Melamine-Barbiturate-2-Thiobarbiturate: Experimental and Theoretical Studies

In this work, we considered the formation of supramolecular assemblies of melamine-thiobarbiturate and melamine-barbiturate-thiobarbiturate. It is known that thiobarbituric acid can form many tautomers, as well as different motifs due to the change of C2=O to C2=S hydrogen bonds. We formed the crystal. The resulting crystals were studied with scanning electron microscopy (SEM), optical fluorescence microscopy, single crystal and powder (PXRD) X-ray diffraction analyses, and solid state nuclear magnetic resonance (ss NMR). These systems were theoretically studied using density functional theory (DFT) and classical molecular dynamics (MD) simulations. Interestingly, just as in the case of melamine barbiturate, during the crystallization process, hydrogen from the C5 moiety of thiobarbituric acid migrates to the melamine molecule. In addition, the resulting melamine thiobarbiturate crystals exhibit fluorescence behavior in the red region (~565–605 nm), while the melamine barbiturate crystals are fluorescent in the green region (512–542 nm).

Structural, electronic and mechanical properties of double core carbon nanothreads

The synthesis of double core carbon nanothreads (NTHs) has been recently achieved through compression of aromatic molecules containing two rings connected by short chains featuring either double or triple bonds (such as stilbene, azobenzene and diphenylacetylene). Their structure are characterized by two conventional 1D NTHs cores, interconnected by covalent bonds arranged in several ways. In this paper, we provide a comprehensive analysis of the possible atomic structures for double core NTHs, evaluate their relative stability, and calculate some electronic and mechanical properties, using Density Functional Theory calculations and Molecular Dynamics simulations. Many isomers are possible for these 1D materials, differing by the intrinsic structure of the cores and the nature of the covalent bonds crosslinking them. For stilbene and diphenylacetylene NTHs, the most stable isomers feature continuous sp3 or sp2 C-C chains connecting the cores, while those that preserve the original unsaturation of the molecule (azo group) are the most stable for azobenzene. The mechanical behavior of these NTHs are similar to that of conventional single core ones, with enhanced 1D strength and stiffness when continuous chains connect the cores. Their electronic behavior range from metallic to insulating depending on the arrangement of the bonds connecting the cores, and the materials with the narrowest band gaps feature electron delocalization along the chain connecting the cores. The variations in properties associated to the presence of bonds connecting the cores bring new opportunities to the design of electronic and optical devices employing this class of strong and flexible materials.

Automated potential development workflow: Application to BaZrO3

We present a Python workflow, Automated Potential Development (APD), for automating the development of interatomic potentials, including calculation of density functional theory (DFT) fitting data, optimization of potentials, and potential-driven molecular dynamics (MD) simulations. The workflow currently supports CASTEP and VASP DFT codes and the MEAMfit potential optimization code for optimization of reference-free modified embedded atom method (RF-MEAM) potentials. The LAMMPS software is supported for calculating the relaxed geometry, elastic constants, phonon dispersion, thermal expansion and radial distribution functions using the optimized potentials. These same properties are also computed at the DFT level and APD automatically generates plots and tables of these data. Query-by-committee active learning is supported, using multiple fitted potentials to evaluate the energies of atomic configurations generated from LAMMPS MD runs. The workflow is demonstrated on BaZrO3, an oxide-based perovskite material, with RF-MEAM results found in good agreement with DFT. Program summaryProgram title: Automated potential development (APD) workflowCPC Library link to program files:https://doi.org/10.17632/pd9gbxyy8d.1Developer's repository link:https://gitlab.com/AndyDuff123/meamfitLicensing provisions: BSD 3-clauseProgramming language: Python, BashNature of problem: Development of new interatomic potentials is a time-consuming process and requires expertise in density functional theory (DFT), potential optimization, and molecular dynamics (and statics) simulations using the optimized potential. Furthermore repeated cycles are usually required to fix numerical issues and improve the potential, requiring further DFT calculations and potential reoptimization. There are also many tedious steps including setting up inputs, submitting jobs (including continuation jobs where jobs terminated prematurely), analyzing outputs, and validating predictions of the interatomic potential. The latter requires multiple calculations of properties computed at both the DFT and potential level.Solution method: The APD workflow provides a black-box solution to fully automate the generation of interatomic potentials. The workflow takes as input a Materials Project id and temperature range of interest. All DFT, potential optimization, and potential molecular dynamics simulations are automatically set-up, submitted and analyzed. Active-learning is incorporated, and properties are computed both at the DFT and potential-level for validation purposes, with tables and graphs for relaxed geometry, elastic constants, phonon dispersion, partial radial distribution functions, and thermal expansion automatically generated.Additional comments including restrictions and unusual features: A full guide to installation, including setting up an environment with all relevant packages and libraries, are included in the distribution. The APD workflow is currently restricted to RF-MEAM potentials and the properties listed above. Some materials which are particularly challenging at the DFT level, e.g. complex magnetic structures, may require intervention in tuning DFT input parameters.

Adsorption and Corrosion Mitigation Effect of Two New Salen-type Schiff Bases on Mild Steel in Acidic Medium: Experimental and Computational Studies

The quest for more green inhibitors for suppression of material corrosion continues to appreciate due to rising industrialization and advancement in technology. In this work, the abilities of two new salen-type Schiff bases: bis(3,5-dibromosalicylaldehyde) ethylenediamine (DBSE) and bis(3,5- dichlorosalicylaldehyde) ethylenediamine (DCSE) to suppress corrosion of mild steel in 1 M HCl solution were investigated by weight loss method, scanning electron microscopy (SEM), conceptual DFT calculation and molecular dynamics (Monte-Carlo) simulation. The results showed that these compounds are excellent suppressors of mild steel degradation in the acid solution as the degradation process was efficiently retarded to the tune of 92.9% and 97.5% by DCSE and DBSE, respectively at 500 µM inhibitor concentration and 313 K. Suppression efficiency was found to increase with concentration and decrease at elevated temperature due to prevalence of desorption. Adsorption of the inhibitor molecules on mild steel surface occurred by physisorption and in compliance with the Temkin isotherm. The results of SEM analysis confirmed successful formation of protective layers of the inhibitor molecules on the steel surface. Interaction descriptors from DFT calculations and Monte Carlo simulations confirmed the observed ranking of suppression ability as DBSE > DCSE with suspected contributions from both the neutral and protonated forms of the Schiff bases. We conclude that both DCSE and DBSE can be deployed as efficient green inhibitors for the mitigation of mild steel corrosion especially at low to moderately high temperatures.

Design and performance analysis of a PV-assisted alkaline electrolysis for hydrogen production: An experimental and theoretical study

The PV assisted alkaline electrolysis cell was established for hydrogen generation. Lab-made AgNiCu modified nickel foam cathodes were used in this system. The characterization was achieved using field emission scanning electron microscopy, energy-dispersive X-ray and X-Ray diffraction analysis. The electrochemical performance was investigated via linear sweep voltammetry, cyclic voltammetry, Tafel polarization measurements and electrochemical impedance spectroscopy. The electrolysis potential and time depended efficiency was monitored. The structural theoretical analysis of the electrode surface and hydrogen evolution characteristics were also determined applying Density Functional Theory and Ab-initio Molecular Dynamics simulations which identified the role of Ag decoration and Cu incorporation on the surface against water and proton adsorptions. The modified cathode (AgNiCuF) improved the hydrogen production performance owing to lower hydrogen onset potential (−1.1 V) and charge transfer resistance (0.362 ohm at −1.5 V).

Assessment of New Imidazol Derivatives and Investigation of Their Corrosion-Reducing Characteristics for Carbon Steel in HCl Acid Solution

This study assessed the corrosion inhibitory and adsorption properties of two imidazol derivatives, namely 5-((2,4,5-triphenyl-1H-imidazol-1-yl)methyl)quinolin-8-ol (TIMQ) and 5-((2-(4-chlorophenyl)-4,5-diphenyl-1H-imidazol-1-yl)methyl)quinolin-8-ol (CDIQ), on carbon steel (CS) in 1 M of HCl using electrochemical methods, including electrochemical impedance spectroscopy (EIS), potentiodynamic polarization measurements (PDP), UV–visible spectroscopy (UV–v), scanning electron microscopy (SEM), and molecular modeling. The findings showed that TIMQ and CDIQ were potent inhibitors with inhibition efficiencies of 94.8% and 95.8%, respectively. The potentiodynamic polarization experiments showed that the inhibitors worked as mixed-type inhibitors, and the impedance investigations supported the improvement of a protective layer for the inhibitor on the metal surface. Each inhibitor was adsorbed onto the carbon steel surfaces, according to the Langmuir adsorption method. The steel was shielded from acidic ions by an adsorbed coating of the inhibitor molecules, according to SEM. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations were used to inspect the results, and a good correlation was found between these results and those of the study. This information can be applied to determine the effectiveness of inhibitors in a HCl acid solution.

First-principles calculations of the solvent effects on magnesium polysulfides in magnesium-sulfur batteries

Magnesium-sulfur (Mg-S) batteries have gained much attention in research community of rechargeable magnesium batteries (RMBs) due to the high energy density, safety, and low cost. The main challenge in the development of practical Mg-S batteries is the dissolution of intermediate magnesium polysulfides (Mg-PSs) in the electrolyte and their migration to the Mg anode, which results in the notorious shuttle effect. In this study, we combine static density functional theory (DFT) calculations and molecular dynamics (MD) simulations to explore the solvated structures of Mg-PSs with different solvents (THF, DOL and DME) and the reduction processes of solvated Mg-PSs, and the diffusion of S8 for the first time, helping to address the challenges of developing novel electrolytes for Mg-S batteries. Our results demonstrate the effect of solvents on the electrochemical reactions of S cathode in Mg-S batteries and could contribute to the advancement of efficient and high-energy Mg-S batteries.