Dissociation Energy Research Articles

Small molecule activation by sila/germa boryne species.

The inability of p-block elements to participate in π-backbonding restricts them from activating small molecules like CO, H2 , and so forth. However, the development of the main group metallomimetics became a new pathway, where the main-group elements like boron can bind and activate small molecules like CO and H2 . The concept of the frustrated Lewis pair, Boron-Boron multiple bonds, and borylene are previously illustrated. Some of these reported classes of boron species can mimic the jobs of the metal complexes. Hence, we have theoretically studied the binding of CO/N2 molecules at B-center of elusive species like sila/germa boryne stabilized by donor base ligands (cAAC)BE(Me)(L), where E  Si, L  cAACMe , NHCMe , PMe3 , E  Ge, L  cAACMe and (NHCMe )BE(Me)(cAACMe )). The substitutional analogues of (cAACR )BSiR1 (cAAC) and E  P, L  cAACMe ) have been studied by density functional theory (DFT), natural bond orbital, QTAIM calculations and energy decomposition analysis (EDA) coupled with natural orbital for chemical valence (NOCV) analyses. The computed bond dissociation energy and inner stability analyses by the EDA-NOCV method showed that the CO molecule can bind at the B-center of the above-mentioned species due to stronger σ-donor ability while binding of N2 has been theoretically predicted to be weak. The energy barrier for the CO binding is estimated to be 13-14 kcal/mol by transition state calculation. The change of partial triple bond character to single bond nature of the BSi bond and the bending of CBSi bond angle of sila-boryne species are the reason for the activation energy. Our study reveals the ability of such species to bind and activate the CO molecule to mimic the transition metal-containing complexes. We have additionally shown that binding of Fe(CO)4 and Ni(CO)3 is feasible at Si-center after binding of CO at the B-center.

Electrochemical Ammonia Production from Wastewater in a Flow Cell Reactor

Although its high carbon footprint, the Haber-Bosh (HB) process mainly dominates the NH3 production market. Indeed, H2 is mainly produced by fossil fuels steam reforming processes and the catalytic reaction between N2 and H2 requires high energy input, being carried out at high temperatures and pressures. Moreover, it should be considered that HB plants are not evenly distributed in the world, thus NH3 and its derivates transportation to the final user is a large portion of the overall environmental impact.1 Moreover, as the population is growing, the NH3 demand is increasing fast to sustain the massive fertilizer utilization.For these reasons, in the last years, the research has focused on the possibility of producing ammonia from direct nitrogen electrochemical reduction (NRR) in aqueous electrolytes under ambient conditions exploiting renewable energy. This process is limited by low selectivity at high current densities and low yield, due to the high dissociation energy of the N2 triple bond and the unavoidable hydrogen evolution reaction (HER).2 On the other hand, NO3 - can be easily converted into NH3 thanks to the lower activation energy, which makes the reaction thermodynamically favoured compared to N2 reduction.3 Due to the massive agriculture, NO3 - is one of the most abundant contaminants of underground waters and high levels in the human body can cause many diseases. Thus, the use of NO3 - to produce NH3 under ambient conditions can be carried out with lower energy consumption, but can also address the water pollution issue.4 The aim of our work is to assess the catalytic activity of commercial MoS2 and a synthesised Bi-based catalyst in a gas-diffusion electrode flow cell of 10 cm2 geometrical area. Such a setup has the advantage of guaranteeing a better mass transport of the active species and of being scaled up. The electrodes are mainly made by airbrush deposition of a catalyst ink on a carbon paper support, which allows obtaining a high electrochemical active surface as a result of its high porosity. Catalyst loading and NO3 - concentration was varied to find the optimal condition in terms of Faraday efficiency (FE) and yield. MoS2 catalyst showed good catalytic activity towards NH3, with a FE between 62%-77% and yield between 2.9-13 mmol g-1 h-1. On the other hand, synthesised Bi material showed 21% FE and 0.41 mmol h-1 g-1, probably due to Bi final oxidation state, which is not so active towards NH3 production. NH3 quantification has been carried out through UV-vis colourimetric method, using both Nessler’s and Berthelot’s reagents. Even if the concentration of NH3 is high enough to exclude that it can derive from contamination, more sensitive quantification is needed for these experiments, together with the quantification of side products, such as NO2 -, H2 and N2.

(Invited) Solvation Control in Deep Eutectic Solvent Electrolytes for Stable Plating/Stripping of Zn in Battery Applications

Within the field of battery applications, deep eutectic solvents (DESs) have emerged as innovative electrolytes for rechargeable Zinc-ion batteries (ZIBs) . ZIBs traditionally employ neutral or weakly acidic aqueous electrolytes, which are susceptible to the standard anode drawback such as dendrite formation and passivation. DES-based electrolytes can facilitate the reversible plating and stripping of Zn, mitigating also dendrite growth . One notable benefit of DES solvents over their aqueous counterparts is that the concentration of electroactive species controls the shape evolution of electrodes during electroplating. For this reason, the coordination chemistry and metal complex formed between the Lewis acid of the metal and the Lewis base of the DES play a central role. Moreover, water can be added to the eutectic mixtures to increase the diffusion coefficient of the electroactive species and lower the electrolyte viscosity without destroying the eutectic nature if the concentration is kept under 40%.Regarding metal plating/stripping processes, DESs offer a notable advantage due to their high capacity to dissolve metal salts, oxides, and hydroxides, inhibiting the formation of insoluble oxides and hydroxides . Moreover, the unique coordination properties of Zn2+ in DESs lead to an atypical voltammetric behavior, characterized by a cathodic peak in the cathodic branch of the anodic-going scan. The mechanistic studies of Zn electrodeposition onto glassy carbon (GC) from DESs have concluded that the metal is formed by the reduction of an intermediate Zn-containing species. Finally, the reactivity of choline chloride and ethylene glycol can impact coordination in that these species can be dehydrogenated at negative potential forming RO¯, which can replace one or more chloride ligands in [ZnCl4]2− . The correlation between the chemistry of Zn2+ solutions and DESs is elucidated, and the peculiarities of Zn electrochemistry can be rationalized in terms of the DES–electrode interface structure. Although few studies on hydrated DESs have been conducted, the literature remains scant.Shi et al. conducted a study on DES composed of ZnCl2 and acetamide with different concentration of water. The authors employed various spectroscopic techniques, including FT-IR, Raman, and 17O NMR, to investigate the effect of water on the coordination geometry of Zn2+ and its consequent impact on Zn plating. Interestingly, the authors observed that the addition of small amounts of water, below the threshold for direct water-water interaction, resulted in significant alterations of the Zn2+ coordination geometry. In fact, based on the accepted view that Zn electrodeposition is a process that involves desolvation and charge-transfer steps, [ZnCl(acetamide)2(H2O)]+ was shown to undergo successive deamidation and dehydration, yielding [ZnCl(acetamide)]+ from which the metal center is finally reduced. Although [ZnCl(acetamide)3]+ is the most stable species, the energy barrier for dehydration is significantly lower than that for deamidation. Therefore, [ZnCl(acetamide)2(H2O)]+ with lower dissociation energy is the actual electroactive species . The solvation of Zn also affects the nucleation overpotential, as Zn2+ in hydrated DES exhibits faster desolvation kinetics, resulting in a lower nucleation overpotential. In addition, Zhao et al. investigated the properties of a “water-in-DES” electrolyte (~30 mol.% H2O) based on the urea/LiTFSI/Zn(TFSI)2 mixture and discovered that the preferential interaction between water and metal cations promotes interfacial charge transfer. Notwithstanding the important contribution of these papers, the mechanism of Zn electrodeposition in DES has not been conclusively assessed. To address this knowledge gap, our research aims to investigate Zn electrodeposition from two distinct, hydrated DESs: ChU and ChEG with approximately 30% H2O content. To gain control of the impact of the cathode material, we carried out our electrochemical tests by employing GC, Zn, Pt and Au electrodes. Furthermore, to evaluate the performance of these electrolytes under realistic device conditions, electrochemical cycling tests were conducted on symmetric CR2023 coin cells.In this study, we have demonstrated the beneficial effect of water addition on reducing the electrolyte viscosity, which consequently resulted in lower anodic and cathodic overpotentials and improved charge/discharge cyclability. Specifically, the electrolytes ChEG and ChU failed due to passivation and short circuits, respectively. The ChU electrolyte showed regular chronopotentiometric transients until cell failure, and this was supported by multiple cyclic voltammetry (CV) measurements, which showed reversible Zn plating/stripping in this system. Notably, our cell cycling tests were performed at higher current densities and exhibited longer lifetimes compared to previous literature reports. The unusual CV patterns observed with gold and glassy carbon (GC) electrodes, featuring cathodic peaks on both forward and backward scans, were elucidated using complementary electrochemical and in situ Raman spectroscopy measurements. Figure 1

Re(bipyridine)-Polypyrrole Monolayer Deposition on Nanoporous Carbon Scaffolds for Electrochemical CO2 Reduction

The CO2 concentration in the atmosphere has increased from 280 ppm in 1750 to nearly 420 ppm in 2022, leading to multiple environmental issues. Thus, developing an efficient approach for the conversion and use of CO2 is one of our most pressing objectives today. Among different strategies to remove CO2, the electrochemical conversion of CO2 to carbon-based fuels is actively being pursued by many researchers. However, CO2 is thermodynamically quite stable (the dissociation energy of a C=O bond is approximately 750 kJ mol-1) and thus the activation of the bonds in CO2 requires a considerable overpotential, especially when carried out at low temperatures in aqueous solutions, resulting in low efficiency. Although a range of gaseous and liquid products, including formic acid, carbon monoxide, methane, ethylene, and ethanol, can be produced by transferring multiple protons and electrons, the formation of CO is simpler and more straightforward for industrial adoption. In this process, renewable energy would be used to operate the CO2 electrolyzer to convert CO2 to CO, which can then be utilized as a chemical feedstock to produce a variety of fuels [1].Molecular catalysts have been widely studied for CO2 reduction, with research on the development of solid hybrid systems that comprise an immobilized catalyst on a support well underway. This method offers further advantages, as it can further facilitate catalyst recyclability and product separation. Carbon-based materials are the most extensively employed supports discussed in the literature, due to their low cost, high electrical conductivity, and flexibility. [Re(2,2′-bipyridine)(CO)3Cl] ([Re(bpy)]), commonly known as Lehn's catalyst, is among the most extensively studied molecular electrocatalysts for the selective CO2 reduction to CO. While various studies have focused on its optimization, showing excellent performance in organic solutions, CO2 reduction should ultimately be accomplished in aqueous media. Despite the fact that hybrid systems eliminate the requirement for aqueous solubility of the catalyst, examples of immobilized [Re(bpy)] for the stable and effective CO2-to-CO conversion in water remain uncommon.In our previous work, the [Re(4-(4-aminophenethyl)-4′-methyl-2,2′-bipyridine)(CO)3Cl] ([Re-(NH2-bpy)]) complex was synthesized and covalently anchored to a colloid-imprinted carbon (CIC) powder by the oxidation of its amino group. The CICs have a large surface area, homogeneous and controllable pore sizes, and ultra-low tortuosity. While the Re/CIC catalyst converted CO2 to CO with a high selectivity of 93% and a Re-based TON of around 900, its stability was poor and the coverage of the CIC by the Re catalyst was quite low [2]. In later work, catalyst anchoring on the CIC surface was achieved by electrochemical polymerization of the pyrrole group attached to the complex, producing uniform films that exhibited Faradaic efficiencies from 90-100% as well as very good long-term stability under catalytic conditions, producing CO with a selectivity of over 70% for at least 24 hours [3].Herein, we report a similar [Re(bpy)] hybrid electrode constructed by covalent surface tethering of the Re catalyst via pyrrole polymerization but using a self-supported nanoporous carbon scaffold. The advantages of adopting the NCS as opposed to powdered supports include the lack of needed binder, which can cover active sites, the ease of imaging the catalyst before and after testing, and the ability to carry out flow through experiments to overcome mass transport issues and also local pH effects. The CO2RR tests were performed in an H-cell using a KHCO3 solution saturated with CO2, while the catalyst was loaded onto the NCS either by immersing the NCS in a 5 mM Re solution followed by electrodeposition in a Re-free solution (Method A), or by electrodeposition at slow sweep rates in the Re-containing solution (Method B). The bare NCS was studied first, showing the exclusive production of hydrogen, similar to the CIC powders, whereas our hybrid electrode generated 100% CO between -0.4 and -0.7 V vs. RHE. Method A showed that the number of immersion steps used for Re deposition correlated with the coverage of the NCS by the catalyst, in turn giving higher selectivity, higher activity, and a significantly higher TOF (0.13 s-1 vs. 0.03 s-1, found with the CICs). This is due to better [Re] utilisation within the NCS pores (more electroactive [Re]) and a better morphology, retaining the open pores after catalyst deposition. However, the durability was compromised at higher CO2RR rates. In comparison, Method B showed similar excellent performance metrics, while also exhibiting better reproducibility for samples prepared identically. References Jin, S., et al., Angewandte Chemie, 2021. 133(38)Willkomm, J., et al., ACS Applied Energy Materials, 2019. 2(4)Willkomm, J., et al., ACS Catalysis, 2021. 11(3)

Predicting Autoxidation of Sulfides in Drug-like Molecules Using Quantum Mechanical/Density Functional Theory Methods.

Autoxidation of drugs and drug-like molecules is a major concern in the development of safe and effective therapeutics. Because active pharmaceutical ingredients (APIs) that contain sulfur atoms can form sulfoxides under oxidative stress, predicting oxidative susceptibilities within an organic molecule can have a major impact in accelerating the compound's stability assessment. For investigation of a sulfur atom's oxidative stability, density functional theory (DFT) methods were applied to accurately predict S-O estimated bond dissociation enthalpies (BDEs) of sulfoxides. Our process employed B3LYP/6-31+G(d) for geometry optimization and frequency calculation, and we employed B3P86/6-311++G(2df,2p) to obtain electronic energies from single-point energy calculations. A total of 84 drug-like molecules containing 50 different sulfide scaffolds were used to develop a risk scale. Our results showed that when S-O BDE is less than 69 kcal/mol, the sulfur atom has low oxidative susceptibility. High oxidation risk occurs when the S-O BDE is greater than 75 kcal/mol. The risk scale was successful in predicting the relative propensities of sulfide oxidation among the small organic molecules and commercial drugs examined.

Parameters inversion of ZnS multi-phonon absorption model based on the transmissivities in variable temperature

In order to solve the difficulty of characterizing the optical constants of ZnS at high temperatures, the multi-phonon absorption dielectric function model which includes temperature parameters is constructed and modified in this paper. The multi-phonon absorption parameters of ZnS have been inverted based on variable temperature infrared transmittance spectra. The variable temperature infrared transmittance spectra of ZnS have been well fitted. The temperature dependence of the dissociation energy of ZnS materials is demonstrated, and the optical constants of the ZnS material have been obtained at 25 °C, 100 °C, 200 °C, 300 °C, and 400 °C.

Theoretical study about the thermal stability and detonation performance of the nitro-substituted derivatives of 4-(1H-1,2,4-triazol-1-yl) pyrimidine

The nitro groups are introduced into 4-(1H-1,2,4-triazol-1-yl) pyrimidine to substitute the hydrogen atoms successively, through which a total of 31 derivatives are constructed to look for high energy density compounds (HEDCs). To probe the thermal stabilities, the heats of formation (HOFs) are calculated by using the G3MP2 method. To explore the dynamic stability, the natural bond orbital (NBO) analysis is performed to confirm the trigger bond, for which the bond dissociation energy is calculated using the B3PW91 method with the 6-311 + G(d,p) basis set. Furthermore, the detonation velocity (D), the detonation pressure (P), the molecular density (ρ), the explosive heat (Q), and character height (H50) are also predicted. Based on our calculation, it is confirmed that D1, D2, D5, and E are potential high-energy-density compounds with sufficient stability and excellent detonation performance.

EVALUASI SENYAWA BIOAKTIF Nasturtium montanum Wall. SEBAGAI KANDIDAT AGEN ANTIPIRETIK TERHADAP RESEPTOR PROSTAGLANDIN SYNTASE 2 (PTGS2) SECARA IN SILICO [Evaluation of Bioactive Compounds of Nasturtium montanum Wall. as Antipyretic Agent Candidate Toward Prostaglandin Syntase 2 (PTGS2) Through in Silico]

The inhibition of prostaglandin syntase 2 ( PTGS2 route is necessary in order to prevent an feverfever. Antipyretic drugs such as the Non steroids ( NSAIDs are fever medication which acts as non-selective inhibitor of PTGS2. NSAID overdose cases have led to herbal ingredients utilization as alternative remedies, such as the Nasturtium montanum leaves. This research aimed to observe the interaction of selected bioactive compounds within N. montanum with the PTGS2 target protein through molecular docking. In addition, this research used in silico approach conducted with molecular docking method trough several stages such as preparation of 3D ligand structure and protein, protein sterilization by PyMOL, docking compounds with PyRx and visualization of docking results via LigPlot+. Results obtained from this research shows the bond dissociation energy value of 1-O-sinapoyl-beta-D-glucose, kaempferol 3-O-sophoroside, patuletin 3-gentiobioside and quercetin 3-O-malonylglucoside substances are smaller compared to meclofenamic acid causing the four ligand tests more stable in their binding to PTGS2 receptor. Meclofenamic acid and 1-O-sinapoyl-beta-D-glucose both bind to PTGS2 receptor with the same amino acid residue as well as the same interaction. Whereas meclofenamic acid, kaempferol 3-O-sophoroside, patuletin 3-gentiobioside and quercetin 3-O-malonylglucoside bind to PTGS2 receptor with the same amino acid residue yet have different bond interaction.

Preparation and properties of highly refractive SmO3/2-TiO2-HfO2 glasses by aerodynamic levitation

The SmO3/2-TiO2-HfO2 (STH) glasses system was successfully prepared using the aerodynamic levitation technique. XRD analysis confirms that the obtained samples are amorphous. Raman spectra demonstrate that the maximum phonon energy is 1060 cm−1. DSC measurements reveal that the addition of HfO2, with its high melting point, increases both Tx and Tg. The maximum ΔT reaches 75.7 °C, and the density of the glass increases from 5.0548 to 5.1097 g/cm3. When the HfO2 content is kept constant, a decrease in Sm2O3 content and an increase in TiO2 content lead to a decrease in Tg and Tx, with a corresponding increase in density. The glass exhibits a maximum Vickers hardness of 8.102 GPa, which can be attributed to the high dissociation energy of Sm2O3, TiO2, and HfO2. Furthermore, both ST and STH glasses show excellent resistance to acid and alkali corrosion. Additionally, the refractive index contribution of each oxide follows the order: TiO2 > HfO2 > Sm2O3. The refractive index increases with increasing TiO2 and HfO2 content. Therefore, it is necessary to adjust the ratio of each oxide to optimize the values of Vm, OPD, and αO2− for a positive effect on the refractive index. The transmittance of STH glass is approximately 70 %, and the internal transmittance is 90 %. This indicates good transmittance even without considering reflection. The glass has a maximum refractive index of 2.343 and an Abbe number υd in the range of 17.06–18.02, meeting the dispersion requirements of commercial optical glasses. These results suggest that STH glass is a highly refractive optical glass with promising potential for various applications.

First-principles study of H2S adsorption and dissociation on the Ni(111) and Cl-covered Ni(111) surfaces

This article is based on density functional theory to calculate and study the adsorption and dissociation of H2S on Ni(111) and Cl-covered Ni(111) surfaces. The calculation results show that H2S is stably adsorbed at the Top site on both surfaces. There is a certain repulsive effect between Cl and H2S, which leads to a decrease in the adsorption strength of H2S. The dissociation energy barriers of the first step for H2S are higher than those of the second step on both surfaces, indicating that the first step of dissociation is the rate-determining step. In the presence of Cl, the energy barrier for the first step of H2S dissociation decreases from 0.27 eV to 0.19 eV, while the energy barrier for the second step of H2S dissociation increases from 0.01 eV to 0.11 eV. This means that the presence of Cl accelerates the first step of H2S dissociation and hinders the second step. The increase energy barrier for the second step of H2S dissociation implies greater difficulty in breaking the SH bond during this step, so the presence of Cl can inhibit the breaking of the SH bond in the second step. Additionally, the decomposition of H2S on both Ni(111) and Cl-covered Ni(111) surfaces is an exothermic process and a spontaneous one.

Transferable Machine Learning Interatomic Potential for Bond Dissociation Energy Prediction of Drug-like Molecules.

We present a transferable MACE interatomic potential that is applicable to open- and closed-shell drug-like molecules containing hydrogen, carbon, and oxygen atoms. Including an accurate description of radical species extends the scope of possible applications to bond dissociation energy (BDE) prediction, for example, in the context of cytochrome P450 (CYP) metabolism. The transferability of the MACE potential was validated on the COMP6 data set, containing only closed-shell molecules, where it reaches better accuracy than the readily available general ANI-2x potential. MACE achieves similar accuracy on two CYP metabolism-specific data sets, which include open- and closed-shell structures. This model enables us to calculate the aliphatic C-H BDE, which allows us to compare reaction energies of hydrogen abstraction, which is the rate-limiting step of the aliphatic hydroxylation reaction catalyzed by CYPs. On the "CYP 3A4" data set, MACE achieves a BDE RMSE of 1.37 kcal/mol and better prediction of BDE ranks than alternatives: the semiempirical AM1 and GFN2-xTB methods and the ALFABET model that directly predicts bond dissociation enthalpies. Finally, we highlight the smoothness of the MACE potential over paths of sp3C-H bond elongation and show that a minimal extension is enough for the MACE model to start finding reasonable minimum energy paths of methoxy radical-mediated hydrogen abstraction. Altogether, this work lays the ground for further extensions of scope in terms of chemical elements, (CYP-mediated) reaction classes and modeling the full reaction paths, not only BDEs.

Regulating In-MOF derivatives for bidirectionally boosting redox kinetics of sulfur cathodes

Lithium sulfur (Li–S) batteries are regarded as a promising application device due to their high theoretical capacity and energy density. However, the commercialization of Li–S batteries is restricted due to their fast capacity fading caused by the shuttle effect of lithium polysulfide (LiPSs) and slow redox reaction of sulfur cathodes. Designing highly-active bidirectional electrocatalysts is an effective strategy to address the problems caused by complex multi-step reactions. Herein, the phase of In-metal-organic framework (In-MOF) derivatives are regulated by controlling the carbonization temperature, and In–In2O3@C heterostructure composite can be obtained at 800 °C. The results show that the polar In2O3 can not only effectively adsorb LiPSs but also accelerate the conversion from Li2S8 to Li2S4, and In can promote the conversion from Li2S4 to Li2S and simultaneously lower the dissociation energy barrier of Li2S. Due to the different catalytic functions of In and In2O3 for different reaction stages of Li–S batteries, In–In2O3@C shows bidirectionally catalytic effect, and renders the corresponding batteries achieve the best electrochemical properties. The specific discharge capacity of In–In2O3@C/S can reach 1298.5 mAh g−1 at 0.2 C after three cycles of activation, and it keeps 620.9 mAh g−1 after 80 cycles with Coulombic efficiency of approximate 100 %. Regulating the products of MOF derivatives provides a reference for the regulation of catalysts for Li–S batteries.

Ground and excited electronic structures of electride and alkalide units: The cases of Metal-Tren, -Azacryptand, and -TriPip222 complexes.

A systematic electronic structure analysis was conducted for M(L)n molecular electrides and their corresponding alkalide units M(L)n @M' (M/M' = Na, K; L = Tren, Azacryptand, TriPip222; n = 1, 2). All complexes belong to the "superalkali" category due to their low ionization potentials. The saturated molecular electrides display M+ (L)n - form with a greatly diffuse quasispherical electron cloud. They were identified as "superatoms" considering the contours of populating atomic-type molecular orbitals. The observed superatomic Aufbau order of M(Tren)2 is 1S, 1P, 1D, 1F, 2S, 2P, and 1G and it is consistent with those of M(Azacryptand) and M(TriPip222) up to the analyzed 1F level. Their excitation energies decrease gradually moving from M(Tren)2 to M(Azacryptand) and to M(TriPip222). The studied alkalide complexes carry [M(L)n ]+ @M'- ionic structure and their dissociation energies vary in the sequence of K(L)n @Na > Na(L)n @Na > K(L)n @K > Na(L)n @K. Similar to molecular electrides, the anions of alkalide units occupy electrons in diffuse Rydberg-like orbitals. In this work, excited states of [M(L)n @M']0/+/- and their trends are also analyzed.

Highly enhanced bifunctionality by trace Co doping into Ru matrix towards hydrazine oxidation-assisted energy-saving hydrogen production

As an alternative to oxygen evolution reaction (OER), the low-potential hydrazine oxidation reaction (HzOR) can assemble with hydrogen evolution reaction (HER) to fulfill the energy-saving H2 generation, which demands of developing high-quality bifunctional electrocatalysts for HER and HzOR. Herein, a simple one-pot wet-chemical method was employed to facilely prepared the highly dispersed RuCo alloy particles onto oxygenated carbon black (RuCo/C). With the trace doping of Co into Ru matrix, RuCo/C exhibits the significantly boosted bifunctional activity, superior to the recently reported counterparts, with low potentials of –13.3 and –76.8 mV at 10 mA·cm−2 for HER and HzOR, respectively. Additionally, the novel HER||HzOR electrolysis system just requires a small voltage of 215.4 mV at 100 mA·cm−2, and thus is easily operated under low-energy portable external powers (fuel cell and solar cell) with impressive H2 production, demonstrating the superiority in energy saving and convenient operation. Moreover, theoretical calculations unclose upon alloying with trace Co, the H2O dissociation energy barrier and hydrogen ad/desorption of HER can be simultaneously optimized on Ru active sites, and the rate-determining energy barrier of HzOR can be also greatly reduced. This study provides one simple but workable approach to prepare high-performance bifunctional HER and HzOR eletrocatalysts, highly promising for the energy-saving H2 production.

Nonequilibrium Ab Initio Molecular Dynamics Simulation of Water Splitting at Fe2O3-Hematite/Water Interfaces in an External Electric Field.

In the exploration of the optimal material for achieving the photoelectrochemical dissociation of water into hydrogen, hematite (α-Fe2O3) emerges as a highly promising candidate for proof-of-concept demonstrations. Recent studies suggest that the concurrent application of external electric fields could enhance the photoelectrochemical (PEC) process. To delve into this, we conducted nonequilibrium ab initio molecular dynamics (NE-AIMD) simulations in this study, focusing on hematite-water interfaces at room temperature under progressively stronger electric fields. Our findings reveal intriguing evidence of water molecule adsorption and dissociation, as evidenced by an analysis of the structural properties of the hydrated layered surface of the hematite-water interface. Additionally, we scrutinized intermolecular structures using radial distribution functions (RDFs) to explore the interaction between the hematite slab and water. Notably, the presence of a Grotthuss hopping mechanism became apparent as the electric field strength increased. A comprehensive discussion based on intramolecular geometry highlighted aspects such as hydrogen-bond lengths, H-bond angles, average H-bond numbers, and the observed correlation existing among the hydrogen-bond strength, bond-dissociation energy, and H-bond lifetime. Furthermore, we assessed the impact of electric fields on the librational, bending, and stretching modes of hydrogen atoms in water by calculating the vibrational density of states (VDOS). This analysis revealed distinct field effects for the three characteristic band modes, both in the bulk region and at the hematite-water interface. We also evaluated the charge density of active elements at the aqueous hematite surface, delving into field-induced electronic charge-density variations through the Hirshfeld charge density analysis of atomic elements. Throughout this work, we drew clear distinctions between parallel and antiparallel field alignments at the hematite-water interface, aiming to elucidate crucial differences in local behavior for each surface direction of the hematite-water interface.

Screening seven-electron boron-centered radicals for dinitrogen activation.

The activation of dinitrogen is significant as nitrogen-containing compounds play an important role in industries. However, the inert NN triple bond caused by its large HOMO-LUMO gap (10.8 eV) and high bond dissociation energy (945 kJ mol-1 ) renders its activation under mild conditions particularly challenging. Recent progress shows that a few main group species can mimic transition metal complexes to activate dinitrogen. Here, we demonstrate that a series of seven-electron (7e) boron-centered radical can be used to activate N2 via density functional theory calculations. It is found that boron-centered radicals containing amine ligand perform best on the thermodynamics of dinitrogen activation. In addition, when electron-donating groups are introduced at the boron atom, these radicals can be used to activate N2 with low reaction barriers. Further analysis suggests that the electron transfer from the boron atom to the π* orbitals of dinitrogen is essential for its activation. Our findings suggest great potential of 7e boron radicals in the field of dinitrogen activation.

Valorization of carbon dioxide with alcohols

Utilizing CO2 for the production of bulky and valuable chemicals presents an attractive solution to address environmental and fossil energy crises. Among the various approaches, direct carboxylation of alcohols with CO2 stands out as an eco-friendly process capable of efficiently producing carboxylic acids in a sustainable manner. However, the high dissociation energy of the CO bond poses a significant challenge in this process. Over the past few decades, several strategies have been developed to activate alcohols and establish efficient catalytic systems for carboxylation with CO2. Nevertheless, the sporadic nature of reported approaches makes it difficult to determine the most effective one. This perspective aims to provide an overview of the current state-of-the-art catalytic protocols for carboxylating alcohols with CO2, encompassing esterification, halogenation, and photocatalysis, while considering their respective advantages and limitations. We aim to discern the most promising avenues for future development in this field. The insights presented in this perspective will contribute to the advancement of efficient and sustainable carboxylation methods using CO2, leading to the production of valuable chemicals in future.

Exploring the Hydrogen Storage Performance of MgH2 Catalyzed by Two Transition Metals Ni and Co by In‐situ Calorimetry and Density Functional Theory Calculations

AbstractAddressing the drawbacks of magnesium‐based hydrogen storage materials with high thermal stability and slow kinetics of hydrogen absorption and discharge remains a current research challenge. In this paper, MgH2 catalyzed by Ni and Co has been prepared by ball milling. The hydrogen storage performance of the 90MgH2+5Ni+5Co composite has been investigated using common techniques, such as differential scanning calorimetry (DSC) and pressure‐composition‐isothermal (PCI) method. Furthermore, the main focus of the study was to investigate the changes in dehydrogenation enthalpy of MgH2 upon addition of Ni and Co, and the bonding mode during the dehydrogenation process of MgH2 and the dissociation energy barrier of hydrogen molecules on the surface of Mg were calculated using density functional theory. The results showed that the dehydrogenation activation energy of 90MgH2+5Ni+5Co decreased by 55.9 kJ/mol compared with that of MgH2. The dehydrogenation enthalpies of as‐milled MgH2 and 90MgH2+5Ni+5Co were 64.8 kJ/mol H2 and 63.4 kJ/mol H2, respectively. Thus the co‐doping of Ni and Co contributed significantly to decrease the thermodynamic stability and improve the hydrogen sorption kinetic properties of MgH2.

Electronic Structure and Chemical Bonding of the First-, Second-, and Third-Row-Transition-Metal Monoborides: The Formation of Quadruple Bonds in RhB, RuB, and TcB.

Boron presents an important role in chemistry, biology, and materials science. Diatomic transition-metal borides (MBs) are the building blocks of many complexes and materials, and they present unique electronic structures with interesting and peculiar properties and a variety of bonding schemes which are analyzed here. In the first part of this paper, we present a review on the available experimental and theoretical studies on the first-row-transition-metal borides, i.e., ScB, TiB, VB, CrB, MnB, FeB, CoB, NiB, CuB, and ZnB; the second-row-transition-metal borides, i.e., YB, ZrB, NbB, MoB, TcB, RuB, RhB, PdB, AgB, and CdB; and the third-row-transition-metal borides, i.e., LaB, HfB, TaB, WB, ReB, OsB, IrB, PtB, AuB, and HgB. Consequently, in the second part, the second- and third-row MBs are studied via DFT calculations using the B3LYP, TPSSh, and MN15 functionals and, in some cases, via multi-reference methods, MRCISD+Q, in conjunction with the aug-cc-pVQZ-PPM/aug-cc-pVQZB basis sets. Specifically, bond distances, dissociation energies, frequencies, dipole moments, and natural NPA charges are reported. Comparisons between MB molecules along the three rows are presented, and their differences and similarities are analyzed. The bonding of the diatomic borides is also described; it is found that, apart from RhB(X1Σ+), which was just recently found to form quadruple bonds, RuB(X2Δ) and TcB(X3Σ-) also form quadruple σ2σ2π2π2 bonds in their X states. Moreover, to fill the gap existing in the current literature, here, we calculate the TcB molecule.

Molecular Characterization of Mesoporous Silica (Un)loading by Gemcitabine and Ibuprofen – An Interplay of Salt-Bridges and Hydrogen Bonds

The molecular mechanisms of mesoporous silica nanomaterial (MSN) loading by gemcitabine and ibuprofen molecules, respectively, are elucidated as functions of pore geometry. Based on a small series of MSN archetypes, we use molecular dynamics simulations to systematically explore molecule-by-molecule loading of the carrier material. Apart from predicting the maximum active pharmaceutical ingredient (API) loading capacity, more detailed statistical analysis of the incorporation energy reveals dedicated profiles stemming from the interplay of guest-MSN salt-bridges/hydrogen bonding in concave and convex domains of the silica surfaces - which outcompete interactions among the drug molecules. Only after full coverage of the silica surface, we find secondary layer growth stabilized by guest-guest interactions exclusively. Based on molecular models, we thus outline a two-step type profile for drug release from MSN networks. Subject to the MSN structure, we find 50–75 % of the API within amorphous domains in the inner regions of the pores – from which drug release is provided at constant dissociation energy. In turn, the remaining 50–25 % of drug molecules are drastically hindered from dissociation.