Activation Barrier Research Articles

Theoretical investigation of Diels–Alder reaction mechanism and regioselectivity with functionalized fullerene derivatives

AbstractDensity functional theory (DFT) was used to study the mechanism of Diels–Alder (DA) reaction between 2‐Methyl‐ 1,3 Butadiene (MBD) with B12N12, B6N6C12 and B6C12N6 fullerens in the gas phase. In this mechanism, B‐N bonds of four‐membered and six‐membered rings of nanocages were chosen to react with MBD. Due to the existence of two types of B‐N bonds, two competitive pathways (a and b) were investigated. The effect of the substitution of carbon atoms instead of boron and nitrogen atoms on the stability of the structures and the regioselectivity of the DA reaction was examined. The potential energy of all structures and the activation barrier for all reaction pathways was evaluated. The chemical reactivity of fullerens using the molecular quantum descriptors was assessed. To evaluate the global electron density transfer in transition states (TS) structures, the natural bond orbital (NBO) analysis was performed.

Reactions of Aluminum Oxide Cluster Cations with Ethane: A Mass-Spectrometric and Vibrational Spectroscopy Study.

The pathways for the reactions of aluminum oxide cluster ions with ethane have been measured. For selected ions (Al2O+, Al3O2 +, Al3O4 +, Al4O7 +) the structure of the collisionally-stabilized reaction intermediates were explored by measuring the photodissociation vibrational spectra from 2600 cm-1-3100 cm-1. Density functional theory was used to calculate features of the potential energy surfaces for the reactions and the vibrational spectra of intermediates. Generally, more than one isomer contributes to the observed spectrum. The oxygen-deficient clusters Al2O+ and Al3O2 + have large C-H activation barriers, so only the entrance channel complexes in which intact C2H6 binds to aluminum are observed. This interaction leads to a substantial (~200 cm-1) red shift of the C-H symmetric stretch in ethane, indicating significant weakening of the proximal C-H bonds. In Al3O4 +, the complex formed by interactions with three C2H6 is investigated and, in addition to entrance channel complexes, the C-H activation intermediate Al3O4H+(C2H5)(C2H6)2 is observed. For oxygen-rich Al4O7 +, the C2H6 is favored to bind at an aluminum site far from the reactive superoxide group, reducing the reactivity. As expected, oxygen-rich species and open-shell cluster ions have smaller barriers for C-H bond activation, except for Al3O4 + which is predicted and observed to be reactive.

Origins of Catalysis in Non-Heme Fe(II)/2-Oxoglutarate-Dependent Histone Lysine Demethylase KDM4A with Differently Methylated Histone H3 Peptides.

Histone lysine demethylase 4A (KDM4A), a non-heme Fe(II)/2-oxoglutarate (2OG) dependent oxygenase that catalyzes the demethylation of tri-methylated lysine residues at the 9, 27, and 36 positions of histone H3 (H3K9me3, H3K27me3, and H3K36me3). These methylated residues show contrasting transcriptional roles; therefore, understanding KDM4A's catalytic mechanisms with these substrates is essential to explain the factors that control the different sequence-dependent demethylations. In this study, we use molecular dynamics (MD)-based combined quantum mechanics/molecular mechanics (QM/MM) methods to investigate determinants of KDM4A catalysis with H3K9me3, H3K27me3 and H3K36me3 substrates. In KDM4A-H3(5-14)K9me3 and KDM4A-H3(23-32)K27me3 ferryl complexes, the O-H distance positively correlates with the activation barrier of the rate-limiting step, however in the KDM4A-H3(32-41)K36me3, no direct one-to-one relationship was found implying that the synergistic effects between the geometric parameters, second sphere interactions and the intrinsic electric field contribute for the effective catalysis for this substrate. The intrinsic electric field along the Fe-O bond changes between the three complexes and shows a positive correlation with the HAT activation barrier, suggesting that modulating electric field can be used for fine engineering KDM catalysis with a specific substrate. The results reveal how KDM4A uses a combination of strategies to enable near equally efficient demethylation of different H3Kme3 residues.

In-depth investigation of corrosion inhibition mechanism: Computational, electrochemical, and theoretical studies of vanillin meldrum’s acid on mild steel surface in 1 M HCl

Vanillin Meldrum’s acid (VanMA) was successfully synthesized and thoroughly examined using techniques like elemental analysis, FTIR, NMR, UV–Vis spectroscopies, and single crystal X-ray diffraction. It crystallizes in a triclinic crystal system under the P-1 space group. A quantitative analysis of the intermolecular interactions in the crystal structures was performed using Hirshfeld surface analysis, which reveals that H···H contacts are the most significant contributing 43.2 % and the O···H/H···O contacts contributing 36.2 % of the total Hirshfeld surfaces. VanMA proved effective as a corrosion inhibitor in 1 M HCl, demonstrating a 62.19 % inhibition efficiency at an optimal concentration of 0.1 mM. It creates a protective layer on mild steel surfaces, adhering to the Freundlich adsorption isotherm (R2 = 0.9983) and displaying a physical adsorption mechanism (−12.72 kJ/mol). The corrosion inhibition efficacy of VanMA (0.1 mM) decreases in 1 M HCl as the temperature increases from 303 to 383 K. A shift towards physisorption is indicated by the increase in activation energy (Ea) from 12.37 to 16.42 kJ/mol. VanMA’s adsorption efficacy reduces at higher temperatures, increasing surface exposure and corrosion rates, but increasing activation enthalpy (ΔH° = 31.32 kJ/mol) and ΔS° = −113.63 J mol−1 K−1). The diameter of the semicircle rose as the concentration of VanMA increased, indicating that VanMA adsorption is responsible for the mild steel surface’s greater resistance to corrosion with increasing Rct values from 224 to 641 Ω cm2 and decreasing capacitance double layer (Cdl) values from 4.480 × 10−5 to 1.560 × 10−5 μFcm2, confirming VanMA’s efficacy as a corrosion inhibitor at 65.05 %. The SEM-EDX and AFM images show the smoother mild steel surface at 0.1 mM VanMA. VanMA was verified as a mixed-type inhibitor by showing shifts of less than 85 mV with respect to the blank PDP. The inhibition efficiency (IE%) increased up to 77.89 % while the icorr values decreased to 1.1850 × 10−5 A/cm2 as the VanMA concentration rose. In XPS, the presence of VanMA was identified by the presence of FeO (713.60 eV) and CO (287.93 eV), which signifies the adsorption of VanMA onto mild steel by the O atom and the negatively charged O ion via a mixed adsorption. DFT and Mulliken population analysis deduced that the VanMA interacted with the mild steel through mixed adsorption. VanMA adsorbs almost parallel to the Fe (1 1 0) surface, forming a barrier that protects from corrosion, according to the MD modeling. While the significant negative adsorption energy (−309.490 kcal/mol) verifies the stability and spontaneity of the adsorption process.

Rationally Designed L12-Pt2RhFe Intermetallic Catalyst with High CO-Tolerance for Alkaline Methanol Electrooxidation.

It is a grand challenge to deep understanding of and precise control over functional sites for the rational design of highly efficient catalysts for methanol electrooxidation. Here, an L12-Pt2RhFe intermetallic catalyst with integrated functional components is demonstrated, which exhibits exceptional CO tolerance. The Pt2RhFe/C achieves a superior mass activity of 6.43 A mgPt -1, which is 2.23-fold and 3.53-fold higher than those of PtRu/C and Pt/C. Impressively, the Pt2RhFe/C exhibits a significant enhancement in durability owing to its high CO-tolerance and stability. Density functional theory calculations reveal that high performance of Pt2RhFe intermetallic catalyst arises from the synergistic effect: the strong OH binding energy (OHBE) at Fe sites induce stably adsorbed OH species and thus facilitate the dehydrogenation step of methanol via rapid hydrogen transfer, while moderate OHBE at Rh sites promote the formation of the transition state (Pt-CO···OH-Rh) with a low activation barrier for CO removal. This work provides new insights into the role of OH binding strength in the removal of CO species, which is beneficial for the rational design of highly efficient catalysts.

First-principles study of selective CO2 activation to methanol on PdZn/TiO2: Unveiling Zn/Pd ratio on catalysis performance

In this study, a series of Pd(8-n)Znn/TiO2(n=0–8) were investigated via density functional theory (DFT) to understand the influence of Zn/Pd ratio on their catalysis performance of conversion CO2 to methanol. It is revealed that Zn prefers to replace the bottom-layered Pd when its molar concentration in composition increases. For all surface models, interface between cluster and support plays a key role in CO2 stabilization and activation. Increasing Zn/Pd ratio could weaken the binding strength of CO2 over catalyst, which further hinders the “RWGS” pathway while promotes the “Formate” pathway. Based on the calculation results, a Brønsted–Evans–Polanyi (BEP) relation between the activation barrier (Ea) of key elementary steps from both mechanisms and the binding strength of key intermediates has been established, from which the optimum Zn/Pd ratio leading to the best catalysis performance has been determined. Moreover, it is found that water inclusion in the system does not change the Ea of rate-determining step much even though it has a promotion effect on OH formation steps. Overall, this work provides some meaningful insight into the influence of cluster composition on the catalysis performance of PdZn-based catalyst and provides valuable information about rational design of the supported bimetallic catalyst.

Microwave Dielectric Study of Binary Mixture of Ethyl Acetate with Propylene Glycol using Time Domain Reflectometry Technique

Microwave dielectric study for the binary mixtures of ethyl acetate with propylene glycol was performed over the frequency range of 10 MHz –20 GHz and in the temperature range of 288 K to 318 K using time domain reflectometry technique. Dielectric parameters such as static dielectric constant (εs), relaxation time (τ), excess dielectric constant (εs)E, excess inverse relaxation time (1/τ)E, Kirkwood correlation factor (geff), Bruggeman factor (fB) and thermodynamic parameters viz. molar enthalpy of activation, molar entropy of activation were also determined. Variation of measured dielectric and thermodynamic parameters have been used to explain the intermolecular interactions between the ethyl acetate and propylene glycol.

Twisted Nanographenes with Robust Conformational Stability.

Owing to a lack of methodology for rationally and selectively synthesizing twisted nanographenes, it is usually inevitable that we obtain nanographenes as a mixture with various geometries, such as unidirectionally twisted, alternatively twisted, randomly twisted, and even wavy structures, reflecting the high activation barriers among them. Otherwise, they are interconvertible if the barriers are low enough such that only averaged properties can be observed under a thermal equilibrium. Recently, we reported on a double-twisted nanographene containing four [6]helicene units within the skeleton. In this paper, we discuss the robust conformational stability of the nanographene, both experimentally and computationally. The results indicate that the nanographene could only be racemized at temperatures exceeding 200 °C, and the first flip of one of the four [6]helicene units is the rate-degerming step.

Confinement Effects of Two-dimensional Surfaces on Water Adsorption and Dissociation over Pt(111).

It has been established that the confined space created by stacking a two dimensional (2D) surface atop a metal catalyst serves as a nano-reactor. According to recent research, when a graphene (Gr) overlayer encloses a Pt catalyst from above, the activation barrier for the water dissociation reaction, a process with major industrial significance, decreases. In order to investigate how the effect of confinement varies among different two-dimensional (2D) materials, we study the adsorption and dissociation barriers of water molecule on Pt(111) under graphene, hexagonal boron nitride (h-BN), and heptazine-based graphitic carbon nitride (g-C3N4) layers using density functional theory calculations. Our findings reveal that the strength of adsorption does not decrease consistently with a reduction in the height of the 2D overlayer. Furthermore, a smaller barrier is not always the consequence of poorer adsorption of the reactant. We also examine the effect of confinement on the shape of the reaction path, on the frequencies of vibrational modes, and on the rate constants derived using the harmonic transition state theory. Overall, all three of the 2D surfaces cause a decrease in barrier height and a weakening of adsorption, though to differing degrees due to a mix of mechanical, geometric and electronic variables.

Syntheses, Structures, and Thermal Decomposition Kinetics of Two Silver/Copper‐Based Coordination Compounds with 1,2,4‐Triazole‐Containing Ligand

AbstractIn this work, two silver/copper‐based coordination compounds {[Ag(tty)]⋅NO3}n (1) and {[Cu2Cl2(tty)2(H2O)2]⋅Cl⋅NO3 ⋅ (H2O)2}n (2) (tty=1,2,4,5‐tetra(1H‐1,2,4‐triazol‐1‐yl))benzen), were synthesized using the different metal salts under the hydrothermal condition. Structural analyses show that compound 1 features tilted L‐shaped 1D Ag chains structure and compound 2 presents a 2D layer with free Cl−, NO3− and water molecules. The experimental results reveal that 1 displays considerably high thermal stability with the thermal decomposition temperature above 337 °C compared to compound 2, which further exemplifies that the framework structures may have a crucial effect on the resultant thermal stability. Additionally, the non‐isothermal kinetics parameters were evaluated at different heating rates by Kissinger's and Ozawa‐Doyle's methods. Importantly, the kinetic triplets (the apparent activation energy (Ea), the preexponential factor (logA) and the mechanism function (ƒ(α)) and the related thermodynamic parameters (the Gibbs energy of activation, ▵G≠, the enthalpy of activation, ▵H≠, and the entropy of activation, ▵S≠) of the thermal decomposition processes are discussed and calculated in detail.

Growth Kinetics of Graphene on Cu(111) Foils from Methane, Ethyne, Ethylene, and Ethane

AbstractChemical vapor deposition of carbon precursors on Cu‐based substrates at temperatures exceeding 1000 °C is currently a typical route for the scalable synthesis of large‐area high‐quality single‐layer graphene (SLG) films. Using molecules with higher activities than CH4 may afford lower growth temperatures that might yield fold‐ and wrinkle‐free graphene. The kinetics of growth of graphene using hydrocarbons other than CH4 are of interest to the scientific and industrial communities. We measured the growth rates of graphene islands on Cu(111) foils by using C2H2, C2H4, C2H6 and CH4, respectively (each mixed with H2). From such kinetics data we obtain the activation enthalpy (ΔH≠) of graphene growth as shown in parentheses (C2H2 (0.93±0.09 eV); C2H4 (2.05±0.19 eV); C2H6 (2.50±0.11 eV); CH4 (4.59±0.26 eV)); C2Hy (y=2, 4, 6) show similar growth behavior but CH4 is different. Computational fluid dynamics and density functional theory simulations suggest that C2Hy differs from CH4 due to different values of adsorption energy and the lifetime of relevant carbon precursors on the Cu(111) surface. Combining experimental and simulation results, we find that the rate determining step (RDS) is the dissociation of the first C−H bond of CH4 molecules in the gas phase, while the RDS using C2Hy is the first dehydrogenation of adsorbed C2Hy that happens with assistance of H atoms adsorbed on the Cu(111) surface. By using C2H2 as the carbon precursor, high‐quality single‐crystal adlayer‐free SLG films are achieved on Cu(111) foils at 900 °C.

Growth Kinetics of Graphene on Cu(111) Foils from Methane, Ethyne, Ethylene, and Ethane.

Chemical vapor deposition of carbon precursors on Cu-based substrates at temperatures exceeding 1000 °C is currently a typical route for the scalable synthesis of large-area high-quality single-layer graphene (SLG) films. Using molecules with higher activities than CH4 may afford lower growth temperatures that might yield fold- and wrinkle-free graphene. The kinetics of growth of graphene using hydrocarbons other than CH4 are of interest to the scientific and industrial communities. We measured the growth rates of graphene islands on Cu(111) foils by using C2H2, C2H4, C2H6 and CH4, respectively (each mixed with H2). From such kinetics data we obtain the activation enthalpy (ΔH≠) of graphene growth as shown in parentheses (C2H2 (0.93±0.09 eV); C2H4 (2.05±0.19 eV); C2H6 (2.50±0.11 eV); CH4 (4.59±0.26 eV)); C2Hy (y=2, 4, 6) show similar growth behavior but CH4 is different. Computational fluid dynamics and density functional theory simulations suggest that C2Hy differs from CH4 due to different values of adsorption energy and the lifetime of relevant carbon precursors on the Cu(111) surface. Combining experimental and simulation results, we find that the rate determining step (RDS) is the dissociation of the first C-H bond of CH4 molecules in the gas phase, while the RDS using C2Hy is the first dehydrogenation of adsorbed C2Hy that happens with assistance of H atoms adsorbed on the Cu(111) surface. By using C2H2 as the carbon precursor, high-quality single-crystal adlayer-free SLG films are achieved on Cu(111) foils at 900 °C.

Highly efficient selective hydrogenation of furfural to tetrahydrofurfuryl alcohol over MOF-derived Co-Ni bimetallic catalysts: The effects of Co-Ni alloy and adsorption configuration

The targeted conversion of furfural (FA) over inexpensive catalyst is a critical and challenging project. Herein, CoNi alloy catalysts (xCoyNi/C) were prepared through one-step pyrolysis of metal–organic frameworks and used in furfural (FA) hydrogenation to tetrahydrofurfuryl alcohol (TFOL). The formation of CoNi alloy leads to a reconfiguration of the electronic structure on the metal surface, which affects the adsorption of functional groups on FA and furfuryl alcohol (FOL). In situ FT-IR analysis and DFT calculations verify that bimetallic CoNi alloy catalyst exhibits more suitable reactants adsorption and hydrogenation rate in comparison with the monometallic Co and monometallic Ni catalysts. Meanwhile, CoNi alloy significantly reduces the activation barrier from FOL to TFOL. Hence, the 1Co1Ni/C catalyst gives the highest TFOL yield of > 99 %. This study provides a simple strategy for the preparation of alloy catalysts for tuning product selectivity and presents practical potential for upgrading biomass-derived platform molecules.

Dielectric relaxation study of pyridine-n-propyl alcohol mixture using time domain reflectometry technique

ABSTRACT The Time Domain Reflectometry (TDR) technique was used to analyse the complex permittivity spectra of the Pyridine-n-propyl alcohol mixture across the concentration and temperature range of 10–25°C. The Cole-Davidson model was used to match the Pyridine- n-propyl alcohol complex permittivity spectra. The nonlinear least squares fit approach has been used to obtain the Static dielectric constant (ε0), Relaxation time (τ), Effective Kirkwood correlation factor (geff) Excess permittivity ε 0 E , Thermodynamic parameters (activation enthalpy and activation entropy), and Bruggeman factor (fB). Furthermore, the analysis of excess characteristics and the Bruggeman factor points towards the presence of hydrogen bonding between the pyridine and n-propyl alcohol molecules.

Towards a complete description of the reaction mechanisms between nitrenium ions and water.

Nitrenium ions are intermediates in the metabolic routes producing the highly carcinogenic nitrosamines and binding to DNA molecules. The reaction mechanism of nitrenium molecules with explicit water molecules is sensibly dependent on the number of waters: when a second molecule is involved, it acts as a catalyst for the reaction, lowering intrinsic activation barriers regardless of the substituent. For all cases, the reaction force constants and reaction electron flux indicate highly synchronous reactions for . Conversely, for highly non-synchronous reactions are obtained, involving two separate proton transfers happening early and late in the reaction path. As a test case, for the simplest reactions, orbital interactions within the NBO paradigm, bond orders, and their derivatives indicate that each individual proton transfer is highly synchronous. Molecular geometries were optimized and characterized at the B3LYP/6-311++G(d, p) level. Intrinsic reaction coordinates were calculated. CCSD(T) single point energies with the same basis were computed on all stationary points. The reaction force, reaction force constant, and reaction electron flux are used to study the evolution of the reacting systems. Natural bond orbitals are used to understand the primitive changes driving the reaction.

Thermodynamics and kinetics of long-range ordering in FCC Ni–33at.%Cr alloys: Insights from atomic scale modeling

This study investigates the thermodynamics and kinetics of the NiCr system, focusing specifically on the kinetics of the order–disorder phase transformation in the Ni–33at.%Cr alloy. Combining density functional theory, CALPHAD-type models, and experimental diffusion data, we introduce and validate an efficient pair interaction model (PIM) and use it in Monte Carlo simulations. Our results include a detailed phase diagram of NiCr in face-centered cubic structure and kinetic models that delineate the behavior of solid solutions at high temperatures and ordered structures at low temperatures. The simulations shed light on tracer diffusion and ordering kinetics within Ni–33at.%Cr, demonstrating good agreement with existing experimental data. Furthermore, our simulation-driven insights prompt a reevaluation of certain aspects of related experimental studies concerning the apparent ordering activation enthalpies and growth kinetics. We also provide a thorough discussion on the strengths of our models and features for future improvement.

Experimental and computational studies of steric factors in the isomerization of internal alkynes within the coordination environment of half-sandwich metal complexes.

The isomerization of internal alkynes Ar1C≡CAr2 within the coordination environment of low-valent half-sandwich [Ru(dppe)Cp]+ complexes via a 1,2-migration process affords vinylidene species [Ru{=C=C(Ar1)Ar2}(dppe)Cp]+. The rearrangement reactions of symmetrically and asymmetrically substituted substrates featuring different electron-donating and -withdrawing groups and of varying steric bulk were modelled using density functional theory (DFT), and the conclusions supported by experimental observations. Examination of the reaction pathway and associated activation barriers reveal a high solvent dependency for the generation of the key intermediate species [Ru(dppe)Cp]+ from [RuCl(dppe)Cp] by Na+ induced halide abstraction , with the lattice enthalpy of the NaCl by-product playing a critical role in the overall thermochemical balance of the reaction. The activation barriers associated with the reaction of [Ru(dppe)Cp]+ with Ar1C≡CAr2, and the relative energies of the alkyne complexes [Ru(h2-Ar1C≡CAr2)(dppe)Cp]+, are sensitive to the electron density of the alkyne and conformational changes associated with the 'bend-back' of the substrate. The latter differs by up to 66.1 kJ/mol, which in turn impacts the barrier height of the subsequent 1,2-migration step . The relative importance of these factors is evinced by the successful rearrangement of the very sterically congested 1(9-anthryl)-2(9-phenanthryl) acetylene into the fully characterized diaryl vinylidene complex, which was isolated in 89% yield.

Synergistic enhancement in hydrodynamic cavitation combined with peroxymonosulfate fenton-like process for bpa degradation: New insights into the role of cavitation bubbles in regulation reaction pathway

The combination of hydrodynamic cavitation (HC) and Fenton-like oxidation technology can dramatically enhance the pollutant removal capacity, however, the synergistic effect of cavitation and catalysts on reactive oxygen species (ROS) generation remained enigmatic. In this study, we established a combined system based on HC and Ce-MnFe2O4 activated peroxymonosulfate (PMS) for BPA removal, and attentions were paid on the role of cavitation bubbles. The results show that the combination of HC in Ce-MnFe2O4 activated PMS could mediate the degradation of BPA from the non-radical pathway dominated by 1O2 to •O2− dominated radical pathway. Both controlled experiments and theoretical calculations revealed that the cavitation bubbles with different sizes play the dominant role in ROS generation. The microjets produced by the collapse of cavitation bubbles could create a large number of oxygen vacancy defects on Ce-MnFe2O4 surface, which modify the activation barrier of PMS and facilitate the generation of •O2− thermodynamically. The stable existing cavitation bubbles with the size of 100∼400 nm could create considerable gas-liquid interface. The molecular dynamics simulations show that the nano bubbles can concentrate the BPA and increase the probability of contacts between BPA and Ce-MnFe2O4, hence effectively solve the issues of short lifetime of •O2− radicals and limited mass transfer distance to strengthen the reaction. In addition, the PMS/Ce-MnFe2O4/HC system not only achieves the satisfied COD (95 %) and TOC (65 %) removal efficiency but also enabled the BPA-contaminated water with a low energy cost of 0.065 kWh·m−3 and oxidant cost, highlighting the application potential of the HC technology for contaminated water.

Mesoporous, high surface area and microrod-shaped cobalt (II) coordination polymer for assessment of molecular structure, thermolysis and non-isothermal kinetics parameters

This study is significant as it presents the assessment of molecular identification, thermal degradation, and non-isothermal kinetics of a cobalt (II) coordination polymer [Co (II) CPs] synthesized from suberoyl bis (2-ethoxybenzamide) (sbebz) and cobalt acetate through the condensation process. The condensation product sbebz was obtained from suberoyl chloride and 2-ethoxybenzamide. The XRD, FT-IR, Raman, and XPS investigated as aspects to identify its structure, purity, and chemical state. The morphological facet was confirmed by SEM and TEM. The morphology data revealed a microrod-shaped morphology of Co (II) CPs with an average particle size 0.7 µm to 1 µm. The pore size, and surface properties were examined by Brunauer-Emmett-Teller (BET) and atomic force microscopy (AFM), revealing a highly large surface area (1076 m2/g), mesoporous and monodisperse nature. The molecular interaction of ligand was estimated using protein molecule. The thermal-decomposition behavior and non-isothermal kinetics of Co (II) CPs were estimated at different heating rates (5 °C/min, 10 °C/min, 15 °C/min, and 20 °C/min) under nitrogen atmosphere by thermogravimetry/Derivative thermogravimetry (TG/DTG). As-synthesized Co (II) CPs show enhanced thermal stability compared to the ligand (sbebz). The multiple heating TG/DTG curve exhibits a more or less identical degradation profile/pattern. The kinetic parameters like order of reaction (n), pre-exponential Arrhenius factor (A), activation entropy (∆s), activation energy (Ea), activation free-energy (∆G), and activation enthalpy (∆H) were calculated using Coats-Redfern (CR) method.

Exploring the potential of two-dimensional MB4 (M=Cr, Mo, and W) monolayer as a high-capacity negative electrode material for Al-ion batteries

Rechargeable metal-ion batteries can employ two-dimensional transition metal tetraboride monolayers because of their numerous accommodating sites, high specific surface area, and layered structure. Li-ion batteries (LIBs) can be efficiently replaced by aluminum ion batteries (AIBs) because aluminum is a cheap and abundant resource. In this work, the density functional theory approach has been used for Al-ion batteries to predict MB4(M= Cr, Mo, W) monolayers performance as anode material. We analyze these monolayers' structures, which are mechanically, thermally, and dynamically stable. Utilizing the energy-efficient adsorption of six Al-atom layers and their lightweight properties, with large storage capacities of 5066 mA h g−1, 3466 mA h g−1, and 2124 mA h g−1, with relatively low average open circuit voltages of 0.18 V, 0.15 V, and 0.11 V for CrB4, MoB4, and WB4, respectively, these monolayers show significant superiority over other 2D anode materials. Likewise, MB4 monolayer showed faster Al ion mobility as seen by the low activation barriers of 0.95 eV, 0.83 eV, and 0.49 eV for CrB4, MoB4, and WB4, respectively. Additionally, even after the full content of Al ions was adsorbed, the metallic characteristics of the materials were mostly retained. These traits suggest that monolayer CrB4, MoB4, and WB4 are promising anode materials for AIBs, with impressive rate capacities.