The regulation mechanism of transition metal doping on Hg0 adsorption and oxidation on Ce/TiO2(001) surface: A DFT study

The mercury oxidation performance of Ce/TiO2 catalyst can be further enhanced by transition metal modifications. This study employed density functional theory (DFT) calculations to investigate the adsorption and oxidation mechanisms of Hg0 on Ce/TiO2(001) and its transition metal modified surfaces. According to the calculation results, Ru-, Mo-, Nb-, and Mn-doping increased the affinity of the Ce/TiO2(001) surface towards Hg0 and HCl, thereby facilitating the efficient capture and oxidation of Hg0. The increased adsorption energy (Eads) of the intermediate HgCl on the modified surfaces could promote its conversion to the final product HgCl2. The modification of transition metals impeded the desorption of the final products HgCl2 and HgO, but it did not serve as the rate-determining step. The oxidation of Hg0 by lattice oxygen and HCl followed the Mars-Maessen and Langmuir-Hinshelwood mechanisms, respectively. HCl exhibited higher mercury oxidation ability than lattice oxygen. The reactivity of lattice oxygen could be further improved by doping transition metals, their promotion order was Ru > Nb > Mo > Mn. In a HCl atmosphere, Mn modification could significantly reduce the energy barrier for HCl activation and HgCl2 formation, providing the optimal enhancement for the mercury oxidation ability of Ce/TiO2 catalyst. The screening method of transition metal modified components based on surface adsorption reaction and oxidation energy barrier was proposed in this study, which provided theoretical guidance for the development of CeTi based catalysts with high mercury oxidation activity.

Comparative study on Perfluoro(2-methyl-3-oxahexanoic) acid removal by quaternary ammonium functionalized silica gel and granular activated carbon from batch and column experiments and molecular simulation-based interpretation

Removing perfluoro(2-methyl-3-oxahexanoic) acid (HFPO-DA) in water treatment is hindered by its hydrophobicity and negative charge. Two adsorbents, quaternary-ammonium-functionalized silica gel (Qgel), specifically designed for anionic hydrophobic compounds, and conventional granular activated carbon (GAC) were investigated for HFPO-DA removal. ANOVA results (p ≪ 0.001) revealed significant effects on initial concentration, contact time, and adsorbent type. Langmuir model-derived capacities were 285.019 and 144.461 mg/g for Qgel and GAC, respectively, with Qgel exhibiting higher capacity irrespective of pH. In column experiments, selective removal of HFPO-DA removal with Qgel was observed; specifically, in the presence of NaCl, the breakthrough time was extended by 10 h from 26 to 36 h. Meanwhile, the addition of NaCl decreased the breakthrough time from 32 to 14 h for GAC. However, in the presence of carbamazepine, neither of the adsorbents significantly changed the breakthrough time for HFPO-DA. Molecular simulations were also used to compare the adsorption energies and determine the preferential interactions of HFPO-DA and salts or other chemicals with Qgel and GAC. Molecular simulations compared adsorption energies, revealing preferential interactions with Qgel and GAC. Notably, HFPO-DA adsorption energy on GAC surpassed other ions during coexistence. Specifically, with Cl- concentrations from 1 to 10 times, Qgel showed lower adsorption energy for HFPO-DA (-62.50 ± 5.44 eV) than Cl- (-52.89 ± 2.59 eV), a significant difference (p = 0.036). Conversely, GAC exhibited comparable or higher adsorption energy for HFPO-DA (-18.33 ± 40.38 eV) than Cl- (-32.36 ± 29.89 eV), with no significant difference (p = 0.175). This suggests heightened selectivity of Qgel for HFPO-DA removal compared to GAC. Consequently, our study positions Qgel as a promising alternative for effective HFPO-DA removal, contributing uniquely to the field. Additionally, our exploration of molecular simulations in predicting micropollutant removal adds novelty to our study.

Single-atom Ag-loaded carbon nitride photocatalysts for efficient degradation of acetaminophen: The role of Ag-atom and O2

Carbon nitride has been extensively used as a visible-light photocatalyst, but it has the disadvantages of a low specific surface area, rapid electron-hole recombination, and relatively low light absorbance. In this study, single-atom Ag was successfully anchored on ultrathin carbon nitride (UTCN) via thermal polymerization, the catalyst obtained is called AgUTCN. The Ag hardly changed the carbon nitride's layered and porous physical structure. AgUTCN exhibited efficient visible-light photocatalytic performances in the degradation of various recalcitrant pollutants, eliminations of 85% were achieved by visible-light irradiation for 1 hr. Doping with Ag improved the photocatalytic performance of UTCN by narrowing the forbidden band gap from 2.49 to 2.36 eV and suppressing electron-hole pair recombination. In addition, Ag doping facilitated O2 adsorption on UTCN by decreasing the adsorption energy from -0.2 to -2.22 eV and favored the formation of O2·-. Electron spin resonance and radical-quenching experiments showed that O2·- was the major reactive species in the degradation of Acetaminophen (paracetamol, APAP).

Defect engineering on electrocatalysts for sustainable nitrate reduction to ammonia: Fundamentals and regulations

Electrocatalytic nitrate (NO3 -) reduction to ammonia (NH3) is a "two birds-one stone" method that targets remediation of NO3 --containing sewage and production of valuable NH3. The exploitation of advanced catalysts with high activity, selectivity, and durability is a key issue for the efficient catalytic performance. Among various strategies for catalyst design, defect engineering has gained increasing attention due to its ability to modulate the electronic properties of electrocatalysts and optimize the adsorption energy of reactive species, thereby enhancing the catalytic performance. Despite previous progress, there remains a lack of mechanistic insights into the regulation of catalyst defects for NO3 - reduction. Herein, this review presents insightful understanding of defect engineering for NO3 - reduction, covering its background, definition, classification, construction, and underlying mechanisms. Moreover, the relationships between regulation of catalyst defects and their catalytic activities are illustrated by investigating the properties of electrocatalysts through the analysis of electronic band structure, charge density distribution, and controllable adsorption energy. Furthermore, challenges and perspectives for future development of defects in NO3RR are also discussed, which can help researchers to better understand the defect engineering in catalysts, and also inspire scientists entering into this promising field.

Amphipathic Phenylalanine-Induced Nucleophilic-Hydrophobic Interface Toward Highly Reversible Zn Anode

Aqueous Zn2+-ion batteries (AZIBs), recognized for their high security, reliability, and cost efficiency, have garnered considerable attention. However, the prevalent issues of dendrite growth and parasitic reactions at the Zn electrode interface significantly impede their practical application. In this study, we introduced a ubiquitous biomolecule of phenylalanine (Phe) into the electrolyte as a multifunctional additive to improve the reversibility of the Zn anode. Leveraging its exceptional nucleophilic characteristics, Phe molecules tend to coordinate with Zn2+ ions for optimizing the solvation environment. Simultaneously, the distinctive lipophilicity of aromatic amino acids empowers Phe with a higher adsorption energy, enabling the construction of a multifunctional protective interphase. The hydrophobic benzene ring ligands act as cleaners for repelling H2O molecules, while the hydrophilic hydroxyl and carboxyl groups attract Zn2+ ions for homogenizing Zn2+ flux. Moreover, the preferential reduction of Phe molecules prior to H2O facilitates the in situ formation of an organic-inorganic hybrid solid electrolyte interphase, enhancing the interfacial stability of the Zn anode. Consequently, Zn||Zn cells display improved reversibility, achieving an extended cycle life of 5250 h. Additionally, Zn||LMO full cells exhibit enhanced cyclability of retaining 77.3% capacity after 300 cycles, demonstrating substantial potential in advancing the commercialization of AZIBs.

Prediction of M3 B4 -type MBenes as Promising Catalysts for CO2 Capture and Reduction

The rational design of novel catalysts with high activity and selectivity for carbon dioxide reduction reaction (CO2 RR) is highly desired. In this work, we have extensive investigations on the properties of two-dimensional transition metal borides (MBenes) to achieve efficient CO2 capture and reduction through first-principles calculations. The results show that all the investigated M3 B4 -type MBene exhibit remarkable CO2 capture and activation abilities, which proved to be derived from the lone pair of electrons on the MBene surface. Then, we emphasize that the investigated MBenes can further selectively reduce activated CO2 to CH4 . Moreover, a new linear scaling relationship of the adsorption energies of potential-determining intermediates (*OCH2 O and *HOCH2 O) versus ΔG(*OCHO) has been established, where the CO2 RR limiting potentials on MBenes are determined by the different fitting slopes of ΔG(*OCH2 O) and ΔG(*HOCHO), allowing significantly lower limiting potentials to be achieved compared to transition metals. Especially, two promising CO2 RR catalysts (Mo3 B4 and Cr3 B4 MBene) exist quite low limiting potentials of -0.48 V and -0.66 V, as well as competitive selectivity concerning hydrogen evolution reactions have been identified. Our research results make future advances in CO2 capture by MBenes easier and exploit the applications of Mo3 B4 and Cr3 B4 MBenes as novel CO2 RR catalysts.

Exploring the structural, electronic, and hydrogen storage properties of hexagonal boron nitride and carbon nanotubes: insights from single-walled to doped double-walled configurations

This study investigates the structural intricacies and properties of single-walled nanotubes (SWNT) and double-walled nanotubes (DWNT) composed of hexagonal boron nitride (BN) and carbon (C). Doping with various atoms including light elements (B, N, O) and heavy metals (Fe, Co, Cu) is taken into account. The optimized configurations of SWNT and DWNT, along with dopant positions, are explored, with a focus on DWNT-BN-C. The stability analysis, employing binding energies, affirms the favorable formation of nanotube structures, with DWNT-C emerging as the most stable compound. Quantum stability assessments reveal significant intramolecular charge transfer in specific configurations. Electronic properties, including charge distribution, electronegativity, and electrical conductivity, are examined, showcasing the impact of doping. Energy gap values highlight the diverse electronic characteristics of the nanotubes. PDOS analysis provides insights into the contribution of atoms to molecular orbitals. UV-Vis absorption spectra unravel the optical transitions, showcasing the influence of nanotube size, dopant type, and location. Hydrogen storage capabilities are explored, with suitable adsorption energies indicating favorable hydrogen adsorption. The desorption temperatures for hydrogen release vary across configurations, with notable enhancements in specific doped DWNT-C variants, suggesting potential applications in high-temperature hydrogen release. Overall, this comprehensive investigation provides valuable insights into the structural, electronic, optical, and hydrogen storage properties of BN and C nanotubes, laying the foundation for tailored applications in electronics and energy storage.

Electrooxidation of chlorophene and dichlorophen by reactive electrochemical membrane: Key determining factors of removal efficiency

This study systematically investigated the variable main electrooxidation mechanism of chlorophene (CP) and dichlorophen (DCP) with the change of reaction conditions at Ti4O7 anode operated in batch and reactive electrochemical membrane (REM) modes. Significant degradation of CP and DCP was observed, that is, CP exhibited greater removal efficiency in batch mode at 0.5-3.5 mA cm-2 and REM operation (0.5 mA cm-2) with a permeate flow rate of 0.85 cm min-1 under the same reaction conditions, while DCP exhibited a faster degradation rate with the increase of current density in REM operation. Density functional theory (DFT) simulation and electrochemical performance tests indicated that the electrooxidation efficiency of CP and DCP in batch mode was primarily affected by the mass transfer rates. And the removal efficiency when anodic potentials were less than 1.7 V vs SHE in REM operation was determined by the activation energy for direct electron transfer (DET) reaction, however, the adsorption function of CP and DCP on the Ti4O7 anode became a dominant factor in determining the degradation efficiency with the further increase of anodic potential due to the disappeared activation barrier. In addition, the degradation pathways of CP and DCP were proposed according to intermediate products identification and frontier electron densities (FEDs) calculation, the acute toxicity of CP and DCP were also effectively decreased during both batch and REM operations.

Toward a mechanistic understanding of Rhenium(VII) adsorption behavior onto aminated polymeric adsorbents: Batch experiments, spectroscopic analyses, and theoretical computations

Rhenium, a rare and critical metal, existing in the industrial wastewater has been aroused extensive interests recently, due to its environmental and resource issues. Chitosan, an easily available, low-cost and eco-friendly biopolymer, was prepared and modified by grafting primary, secondary, tertiary and quaternary amino groups, respectively. Adsorption behaviors and interactions between ReO4- and these four types of aminated adsorbents were investigated through batch experiments, spectroscopic analysis, and theoretical computations. Chitosan modified with secondary amines showed an extremely high uptake of ReO4- with 742.0 mg g-1, which was higher than any reported adsorbents so far. Furthermore, a relatively high adsorption selectivity for Re(VII), as well as the stable and facile regeneration of these aminated adsorbents revealed a promising approach for Re(VII) recovery in full-scale applications. The electrostatic attraction was illustrated to be the main adsorption mechanism by Fourier Transform Infrared Spectroscopy and X-ray Photoelectron Spectroscopy analyses. Significantly, the sub-steps of the adsorption process, encompassing the transformation of binding sites and the subsequent binding between these sites and the adsorbate, have been thoroughly investigated through the density functional theory (DFT) calculation method. This approach was firstly proposed to clearly demonstrate the differences in Re(VII) adsorption behavior onto four types of aminated adsorbents, resulting the importance of not only strong binding energy but also an appropriate binding spatial environmental for effective Re(VII) adsorption.

Adsorption of industry affiliated gases on buckled aluminene for gas sensing applications

INTRODUCTION

First-principles calculations were used to study the adsorption behavior of environmentally significant gases CO, CO₂, NO, NO₂, SO, and SO₂ on pure buckled aluminene (b-Al) for gas sensing applications. Therefore, structural, electronic, and adsorption properties including adsorption energy values and recovery time have been calculated and discussed.

METHODS

All the structures were optimized using Amsterdam Density Functional (ADF) code BAND. In addition, triple zeta polarization basis with slater-type orbitals were utilized.

RESULTS

For every gas analyzed, we observed favorable adsorption energy values and charge transfer occurring between the gas molecule and b-Al. In the valance band, there was a strong hybridization between the p orbitals of gas and b-Al, this led to enhanced conductivity in the density of states (DOS). The recovery time suggested that the adsorption of NO, NO₂, SO, and SO₂ gases on b-Al is good for the application of reversible gas sensors. The recovery time indicated that the b-Al material is very sensitive to NO, NO₂, SO, and SO₂ gas molecules.

CONCLUSION

The conclusion in light of all these results is that b-Al based materials can appear as a probable candidate for high gas sensing performance.

Inhibitory behavior and adsorption of asparagine dipeptide amino acid on the Fe(111) surface

CONTEXT

The inhibitory effect of asparagine (Asn) and its derivatives on iron (Fe) corrosion was studied by performing density functional theory (DFT) calculations. In this paper, the global and local reactivity descriptors of Asn in the protonated and neutral forms were evaluated. Also, the changes in reactivity were investigated when dipeptides were combined with Asn. Due to the increase in the reaction centers within their molecular structure, there was an enhancement in the inhibitory effect of these dipeptides. Moreover, the adsorption energies (E_ads) and the adsorption configurations of Asn and small peptides (SPs) with most stability were determined on the surface of Fe(111). It was found that dipeptides had a chemical adsorption on these substrates. In the protonated forms, there was an enhancement in the absolute values of E_ads between the inhibitors and the Fe(111) surfaces. Peptides were more likely to be adsorbed on the Fe surfaces, showing the great inhibitory effect of these moieties. The results of the current research demonstrate the possibility of utilizing SPs as efficient "green" corrosion inhibitors.

METHODS

DFT computations were undertaken by employing the BIOVIA Material Studio with B3LYP-D3 functional and 6-31 + G* basis set. The theoretical evaluation of the inhibitory effect of asparagine (Asn) dipeptides, and the potential analysis of small peptides to protect against the corrosion of Fe, was done.

Theoretical Sensing Performance for Detection of Cyclophosphamide Drug by Using Aluminum Carbide (C3Al) Monolayer: a DFT Study

Because nanomaterials are highly reactive and electronically sensitive towards a variety of drug molecules, they are thought of as efficient drug sensors. In the present research study, an aluminum carbide (C₃Al) monolayer is employed and its interaction is examined with cyclophosphamide (CP) by performing DFT computations. The C₃Al monolayer is highly reactive and sensitive towards CP according to the computations. CP interacts with the C₃Al monolayer with the adsorption energy of -31.39 kcal/mol. A considerable charge transfer (CT) indicates an enhancement in the conductivity. Also, the charge density is explained based on the electron density differences (EDD). The decrease in CP/C₃Al energy gap (E_g) by approximately 52.91% is due to the remarkable effect of adsorption on the LUMO and the HOMO levels. Therefore, due to the decrease in E_g which can generate an electrical signal, the electrical conductivity is considerably increased. These results suggest that the C₃Al monolayer can be employed as a proper electronic drug sensor for CP. Also, the recovery time for the desorption process of CP form the surface of C₃Al is 351 s at 598 K.

Molecular simulations of the adsorption of aniline from waste-water

Molecular simulations of adsorption processes have received considerable attention. Despite the attention, exploration of the literature shows serious limitations, among which solvent and temperature effects are the most important. In this work, we propose a computational approach to study the adsorption of aniline (as an example of pollutant) from wastewater using coronene as adsorbent. We identified all possible adsorption sites using classical molecular dynamics for further optimization at the ωB97XD/aug-cc-pVDZ level of theory. Three different solvation schemes have been explored: implicit solvation of aniline + coronene, explicit solvation of aniline + coronene, and implicit-explicit solvation of aniline + coronene. For the explicit solvation, we used six water molecules, while the implicit solvation is performed using the PCM (polarizable continuum medium) solvation model. For each of the four cases (gas phase and the three solvation schemes), the adsorption free energy is evaluated as function of temperature from 200 K to 400 K. The results show that solvation has a considerable effects on the adsorption free energy. Furthermore, we noted that the adsorption free energy varies from -39.5 kJ mol^-1 at 200 K to 27.7 kJ mol^-1 at 400 K using the implicit-explicit solvation of aniline + coronene. This result highlights the importance of considering temperature effects in molecular simulations study of adsorption processes.

Insights into the mechanisms of aqueous Cd(II) reduction and adsorption by nanoscale zerovalent iron under different atmosphere conditions

Nanoscale zero-valent iron (NZVI) can effectively remove and recover Cd(II) from aqueous solutions. However, the oxygen effects on Cd(II) removal by NZVI have been overlooked and not well studied. In this research, the Cd MNN auger lines obtained by X-ray photoelectron spectroscopy (XPS) revealed that Cd(II) adsorbed on the NZVI surface could be reduced to Cd(0) by the Fe(0) core under anaerobic conditions. With coexisting oxygen, the Cd(II) removal efficiency declined significantly, and Cd(II) reduction was inhibited by the thickened surface γ-FeOOH layer. Furthermore, the post-oxygen intrusion corroded the generated Cd(0) and led to the dramatic leaching of Cd(II) ions. According to the density functional theory (DFT) simulation, the adsorbed Cd(II) was preferably coordinated via a monodentate model on the surface of Fe₃O₄ and γ-FeOOH, which are the dominant surface species of NZVI under anaerobic and aerobic conditions, respectively. Thus, γ-FeOOH with doubly coordinated hydroxyl groups provided fewer adsorption sites than Fe₃O₄ for Cd(II) ions. Overall, the atmospheric conditions of subsurface remediation and wastewater treatment should be considered when applying NZVI for Cd(II) removal. Favorable atmospheric conditions would improve the efficiency and cost-effectiveness of NZVI-based technologies for the practical remediation of Cd(II) pollution.

A molecular modeling on the potential application of beryllium oxide nanotube for delivery of hydroxyurea anticancer drug

Within this work, we scrutinized the use of BeO nanotube (BeONT) as a nanocarrier for the anticancer drug hydroxyurea (HU) through density functional theory (DFT) calculations. We utilized the functional ꞷB97XD and the basis set 6-31G**. Based on a detailed surface analysis, HU was adsorbed on the surface of the nanotube through 4 different orientations. Also, no vibrational spectra exhibited imaginary frequencies, showing the minimum energy of the relaxed structures. The maximum adsorption energy and the minimum adsorption energy are in strong physical adsorption. The BeONT exhibited p-type semiconducting characteristics in all orientations since it received electronic charge from HU. The results demonstrate the possibility of using the BeONT as a promising carrier for HU drugs.

The interaction between H and CH3 of adsorption on the diamond (100)-2 × 1 surface based on DFT Calculations

In this research, the interaction mechanism between H and CH₃ of chemisorption on diamond (100)-2 × 1 surface was studied through the density functional theory (DFT) method. The H or CH₃ adsorbates were assumed to be directly chemisorbed to the final position on the surface in thermodynamic studies. The adsorption energies of individual H and CH₃ chemisorbed on the diamond surface were calculated, respectively. Subsequently, the adsorption energies for another H or CH₃ in five different positions adjacent to the initial H or CH₃ were calculated and compared. We find the universal law of the most likely chemisorption position. The results revealed that when one carbon atom of the dimer chemisorbed one radical, the other carbon atom of the dimer generated a dangling bond and had more ability to chemisorb other radicals. Therefore, the growth rate is faster along the direction of the carbon dimer than in other directions during the growth of the diamond film. The dimer is exactly towards the [110] direction. As films thicken, diamond tends to grow along the [110] direction. Therefore, it could explain that the [110] texture appears easily in the experiment. And, the results can be used to analyze the detailed process relative to the growth of the diamond film.

Reinforcing the tetracene-based two-dimensional C48H16 sheet by decorating the Li, Na, and K atoms for hydrogen storage and environmental application -A DFT study

To meet the increasing need of energy resources, hydrogen (H₂) is being considered as a promising candidate for energy carrier that has motivated research into appropriate storage materials among scientists. Thus, in this study for the first time, zig-zag and armchair edged tetracene based porous carbon sheet (C₄₈H₁₆) is investigated for H₂ storage using the density functional theory. To explore the hydrogen storage capacity, the hydrogen molecule is initially positioned parallel to the C₄₈H₁₆ sheet at three different sites, resulting in lower adsorption energies of -0.020, -0.024, and -0.015 eV respectively. The Li, Na, and K atoms are decorated to improve H₂ adsorption on the C₄₈H₁₆ sheet. The Li atom decorated C₄₈H₁₆ sheet has a higher binding energy value of -2.070 eV than the Na and K atom decorated C₄₈H₁₆ sheet. The presence of Li, Na, and K atoms on the C₄₈H₁₆ sheet enhance the H₂ adsorption energy than the H₂ on the pristine C₄₈H₁₆ sheet. The decrease of Mulliken charge in alkali metal atoms (Li, Na, and K atom) on the C₄₈H₁₆ sheet reveal that the electron is transferred from H-σ orbital to s orbital of alkali metal atoms on the C₄₈H₁₆ sheet, leads to the enhancement of H₂ binding. Compared to H₂ adsorption on Na and K atom decorated C₄₈H₁₆ sheet, the H₂ adsorption on Li atom decorated C₄₈H₁₆ sheet has the maximum adsorption energy value of -0.389 eV. The obtained hydrogen storage capacity of Li, Na, and K atoms decorated C₄₈H₁₆ sheets are about 7.49 wt%, 7.31 wt%, and 7.14 wt% respectively for four H₂ molecules, which is greater than the targeted hydrogen storage capacity of the United States Department of Energy (DOE). Thus the obtained results in this work reveal that the decorated C₄₈H₁₆ sheets with Li, Na, and K atom plays the potential role in the H₂ storage.

Experimental and DFT investigation on N-functionalized biochars for enhanced removal of Cr(VI)

In this study, N-functionalized biochars with varied structural characteristics were designed by loading poplar leaf with different amounts of urea at 1:1 and 1:3 ratios through pyrolysis method. The addition of urea significantly increased the N content of biochar and facilitated the formation of amine (-NH-, -NH₂), imine (-HCNH), benzimidazole (-C₇H₅N₂), imidazole (-C₃H₃N₂), and pyrimidine (-C₄H₃N₂) groups due to substitution reaction and Maillard reaction. The effect of pH on Cr(VI) removal suggested that decrease in solution pH favored the formation of electrostatic attraction between the protonated functional groups and HCrO₄^-. And, experimental and density functional theory study were used to probe adsorption behaviors and adsorption mechanism which N-functionalized biochars interacted with Cr(VI). The protonation energy calculations indicated that N atoms in newly formed N-containing groups were better proton acceptors. Adsorption kinetics and isotherm experiments exhibited that N-functionalized biochars had greater removal rate and removal capacity for Cr(VI). The removal rate of Cr(VI) on N-functionalized biochar was 10.5-15.5 times that of untreated biochar. Meanwhile, N-functionalized biochar of NB3 with the largest number of adsorption sites for -C₇H₅N₂, -NH₂, -OH, -C₃H₃N₂, and phthalic acid (-C₈H₅O₄) exhibited the supreme adsorption capacity for Cr(VI) through H bonds and the highest adsorption energy was -5.01 kcal/mol. These mechanistic findings on the protonation and adsorption capacity are useful for better understanding the functions of N-functionalized biochars, thereby providing a guide for their use in various environmental applications.

Inter-droplet force between magnetically polarizable Pickering oil-in-water nanoemulsions stabilized with γ-Al2O3 nanoparticles: Role of electrostatic and electric dipolar interactions

HYPOTHESIS

The presence of nanoparticles at oil-water interface influences the interaction forces between Pickering emulsions. When charged nanoparticles are at the oil-water interface of an electrostatically stabilized emulsion, in addition to the screened Coulombic interaction, electric dipolar force also influences the total inter-droplet force profiles. An in-depth understanding of the effects of such electric dipolar forces is essential for designing colloidally stable Pickering nanoemulsions for various applications.

EXPERIMENTS

Inter-droplet forces between γ-Al₂O₃ nanoparticle stabilized oil-in-water nanoemulsion, containing superparamagnetic nanoparticles (magnetically polarizable) in the oil phase, are measured using the magnetic-chaining technique at different pH and salt concentrations. The role of mono-, di- and tri-valent salts on the inter-droplet force profiles are assessed.

FINDINGS

Force measurement studies reveal a lowering of inter-droplet spacing, within the linear chains, for higher salt concentrations due to an increased screening. Strong interfacial attachment of the charged nanoparticles results in the formation of an asymmetric charge cloud leading to an electric dipolar interaction. Incorporating the contributions of electric dipolar and screened Coulombic interactions, the theoretically estimated total repulsive force magnitudes are in good agreement with the experimental data. The obtained results offer better insights into the nature of colloidal force between charged particle stabilized nanoemulsions.

Quantum chemical study the on interaction between sulfanilamide drug and MgO nanocluster

The adsorption and interaction of sulfanilamide (SA) with a pristine magnesium oxide (MgO) nano-cage was scrutinized through density functional theory (DFT) calculations. All geometries were optimized at M06-2X/6-311G(d,p) level, and the single-point energy calculation was also carried out at the same level of theory. Also, natural bond orbital (NBO) analysis was carried out and the values related to Wiberg bond index (WBI), donor-acceptor interactions, and partial natural charges were inspected. The MgO nano-cage can adsorb SA more strongly with the adsorption energy (E_ads) of - 41.74 kcal/mol, corresponding to the stable configurations. In addition, NBO analysis showed that the donor-acceptor interactions with SA and the MgO nano-cage are stronger. Based on our computations, the HOMO-LUMO gap of the MgO nano-cage changed to a great extent following the adsorption of the SA molecule, which corresponds to the most stable configuration that leads to improved electrical conductivity of the MgO nano-cage. The change in the gap determines the sensing mechanism, which is associated with the change in the electrical conductivity. To calculate the recovery time, transition-state theory (TST) was employed. Based on our calculation, Mg₁₂O₁₂-SA complex composites possess a short recovery time for the desorption of SA. The results show that the MgO nano-cage is an ideal candidate to be employed for developing SA sensors with high efficiency.

Detection of 1,1 dimethylhydrazine by graphene oxide: first principles study

The surface of graphene oxide (GO) with different oxidation levels is widely used in gas sensing applications. 1,1-Dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH) as a highly toxic and volatile pollution gas has long been investigated and discussed. The research reported here examined the stable structure of GO surface by first principles calculation. Furthermore, the adsorption mechanism of UDMH on the stable GO surface was explored and the optimal adsorption distance and upper limit of adsorption quantity were determined with their adsorption energy calculated. The results reveal that the hydroxyl group on GO did a great service to the UDMH adsorption and the UDMH tends to approach GO from the direction of -NH₂, with distance being 2.9 Å.

Oxygen-Defect Enhanced Anion Adsorption Energy Toward Super-Rate and Durable Cathode for Ni-Zn Batteries

The alkaline zinc-based batteries with high energy density are becoming a research hotspot. However, the poor cycle stability and low-rate performance limit their wide application. Herein, ultra-thin CoNiO₂ nanosheet with rich oxygen defects anchored on the vertically arranged Ni nanotube arrays (O_d-CNO@Ni NTs) is used as a positive material for rechargeable alkaline Ni-Zn batteries. As the highly uniform Ni nanotube arrays provide a fast electron/ion transport path and abundant active sites, the O_d-CNO@Ni NTs electrode delivers excellent capacity (432.7 mAh g^-1) and rate capability (218.3 mAh g^-1 at 60 A g^-1). Moreover, our O_d-CNO@Ni NTs//Zn battery is capable of an ultra-long lifespan (93.0% of initial capacity after 5000 cycles), extremely high energy density of 547.5 Wh kg^-1 and power density of 92.9 kW kg^-1 (based on the mass of cathode active substance). Meanwhile, the theoretical calculations reveal that the oxygen defects can enhance the interaction between electrode surface and electrolyte ions, contributing to higher capacity. This work opens a reasonable idea for the development of ultra-durable, ultra-fast, and high-energy Ni-Zn battery.

Malachite green adsorption from aqueous solutions onto biochar derived from sheep manure: adsorption kinetics, isotherm, thermodynamic, and mechanism

The adsorption of Malachite Green (MG) from aqueous solution was achieved using biochar derived from sheep manure pyrolyzed at 450 °C. Sheep manure biochar was characterized before and after adsorption of MG by SEM and FTIR. In addition, surface area measurement was performed by BET surface area and pore analyzer. The influence of contact time, pH, dose, temperature, and initial MG concentrations on the adsorption of MG onto sheep manure biochar (SMB) was investigated in experiments. Langmuir, Freundlich, Temkin, and Dubinin-Raduskevich isotherm models were used to analyze the data. Results assumed best fitting model is Langmuir isotherm model (R² value 0.99). Mean free adsorption energy (E) was obtained 94.71 kJ mol^-1, R_L value was between 0.013 and 0.14. That indicates monolayer, favorable, and physisorption adsorption, as well as an endothermic adsorption process. Maximum uptake value from Langmuir model obtained 208.33 mg g^-1. Surface area of SM biochar was 11.731 m² g^-1.NOVELTY STATEMENTThis study is the first study on the adsorption of malachite green dye substance on sheep manure derived biochar.A natural and cheap adsorbent with high dye removal, such as 208,33 mg g^-1.A guiding study for the conversion of agricultural waste into products with highly added value.

Cesium Lead Bromide Perovskite-Based Lithium-Oxygen Batteries

The main challenge for lithium-oxygen (Li-O₂) batteries is their sluggish oxygen evolution reaction (OER) kinetics and high charge overpotentials caused by the poorly conductive discharge products of lithium peroxide (Li₂O₂). In this contribution, the cesium lead bromide perovskite (CsPbBr₃) nanocrystals were first employed as a high-performance cathode for Li-O₂ batteries. The battery with a CsPbBr₃ cathode can exhibit the lowest charge overpotential of 0.5 V and the best cycling performance of 400 cycles among all the reported perovskite-based Li-O₂ cells, which represents a new benchmark. Most importantly, the density functional theory (DFT) calculations further prove that the rate limitation step during OER processes is the decomposition of LiO₂ to form O₂ and Li⁺, and the weak adsorption strength between CsPbBr₃ surfaces and LiO₂ results in a low charge overpotential for the CsPbBr₃-based Li-O₂ battery. This work first demonstrates the good potential of CsPbBr₃ for application in metal-air batteries.

Effective degradation of sulfur mustard simulant using novel sulfur-doped mesoporous zinc oxide under ambient conditions

Sulfur doped metal oxides were synthesized using a two-step precipitation method. When reacted against neat 2-CEES (2-chloroethyl-ethyl sulfide, a mustard gas simulant) under ambient conditions, sulfur doped mesoporous zinc oxide (MS-Zn) showed higher catalytic activity than the other metal oxides with 92.7% overall conversion in 24 h for a 2.5 μL neat 2-CEES droplet added on top of 2 × 2 cm large 400 mg catalyst layer. The reaction proceeded mainly by hydrolysis and further solvolysis reaction also occurred depending on the extracting solvents. Cyclic sulfonium ion intermediate reaction was thought to be involved in this reaction, and metal oxide surfaces were thought to facilitate the formation of sulfonium ions from adsorbed 2-CEES. All other by-products were also found to form via sulfonium ions, reconfirming the well-known importance of this intermediate species for the degradation reaction to proceed. The sulfur content for MS-Zn was varied and tested for degradation of neat 2-CEES. This modification showed that there is an optimal amount of sulfur content for the peak catalytic activity of MS-Zn for 2-CEES degradation. Adsorption energy of a 2-CEES molecule was calculated on model sulfur doped and non doped zinc oxide surfaces and the different adsorption energy levels were correlated with the catalytic activity of sulfur doped zinc oxide.

DFT study of the fouling deposition process in the steam generator by simulating the adsorption of Fe2+ on Fe3O4 (0 0 1)

In order to reveal the fouling problem on the outer surface of the steam generator (SG) tube in the secondary circuit condition of pressurized water reactor (PWR) nuclear power plant, based on the density functional theory (DFT) method, the Cambridge sequential total energy program package (CASTEP) is used to simulate seven kinds of highly symmetric adsorption structure models of termination with tetrahedral Fe (A termination) and termination with octahedral Fe (B termination) on Fe₃O₄ (0 0 1) surface. The adsorption energies and stable adsorption conformations are calculated. The results show that the most stable adsorption structures of the Fe²⁺/Fe₃O₄ (0 0 1) configurations are Fe²⁺ above Fe-O bond of B layer termination (Fe₃O₄(001) A-b). During the adsorption, the Fe-Fe, Fe-O bond length, and Fe-Fe-O bond angle of (0 0 1) surface change, and the atomic positions parallel and perpendicular to (0 0 1) surface change correspondingly. The change happened to the surface layer is the most drastic one. The calculation of charge population, the density of states (DOS), and electron local function of Fe²⁺/Fe₃O₄ (0 0 1) optimal adsorption configuration show that there is electron transfer between Fe²⁺ and Fe₃O₄ (0 0 1), and the adsorption type is chemisorption. Among them, Fe (Fe²⁺)-Fe (Fe₃O₄) forms a metal bond, and Fe (Fe²⁺)-O (Fe₃O₄) forms the ionic bond. The results illustrate the interaction between free Fe²⁺ and Fe₃O₄ is the reason of the nucleation and agglomeration of Fe₃O₄ scale and it provides the foundation for the further research on Fe₃O₄ scale deposition.

Enhancing the degradation of carbamazepine by UVA-LED/WO3 process with peroxydisulfate: Effects of light wavelength and water matrix

In this study, peroxydisulfate (PDS) was used as electron acceptor to improve the photocatalytic activity of WO₃. The results indicated that the degradation of carbamazepine by UVA-LED/WO₃/PDS process followed pseudo-first order and PDS addition significantly enhanced the degradation rate by inhibiting the recombination of electrons and holes. The observed pseudo-first order rate constant (k_obs) was in linear relationship with the dosage of WO₃, while inversely proportional to the initial concentration of CBZ. PDS decreased the k_obs slightly when its concentration exceeded 0.5 mM. The 365 nm UVA-LED performed much better than 385 nm or 405 nm even though its energy efficiency was the lowest. Based on the steady-state kinetic model, sulfate radical was the dominant radical. The effects of water matrix were complex: bicarbonate ion and humic acid showed strong inhibitory effect; increasing the pH above 7 led to significant drop in CBZ removal; sulfate ion slightly decreased the k_obs while 5 mM chloride ion more than doubled the k_obs. The interactions between anions and WO₃ surface were theoretically analysed to explain the effects of anions. The electrical energy per order values suggest that UVA-LED/WO₃/PDS process is suitable for water with low organic carbon.

Data of interaction of supported ionic liquids phases onto copper nanoparticles: A density functional theory study

This work contains data on the computational, structural, and electronic characterization of supported ionic liquids phases anchored to copper nanoparticles using Density Functional theory calculations. The data supplement the paper "Interaction of supported ionic liquids phases onto copper nanoparticles: A Density Functional Theory study" [1], based on the adsorption of ionic liquid onto a Cu nanoparticle is analyzed from a chemical and physical point of view. The chemical analysis is based on Atoms in Molecule theory (AIM) and allows us to differentiate the chemical binding nature between ionic liquid and copper nanoparticle. On the other hand, the energy decomposition analysis based on absolutely localized molecular orbital (ALMO-EDA) describes the physical contributions that govern the interaction between ionic liquid and the copper nanoparticles. Herein, detailed and extended information in the synthesis and computational characterization are presented.

Probing the structural, electronic, and adsorptive properties of Au16O2- clusters

Great progress has been made in O₂ adsorption on gold clusters. However, systematic investigations of O₂ adsorption on [Formula: see text] clusters have not been reported. Here, we present a systematic study of the structural, electronic, and adsorptive properties of [Formula: see text] clusters by density functional theory (DFT) calculations coupled with stochastic kicking method. Global minimum searches for [Formula: see text] reveal that exohedral derivatives are more favored. Furthermore, the obtained ground-state structure exhibits significant stability, as judged by its larger adsorption energy (1.16 eV) and a larger HOMO-LUMO gap (0.57 eV). The simulated photoelectron spectra (PES) of [Formula: see text] isomers will be instructive to identify the structures in future experiments. There are three interesting discoveries in the present paper: (1) O₂ undergoes chemical adsorption onto the parent [Formula: see text] clusters, but the amount of the adsorption energy is related to the parent [Formula: see text] clusters; (2) the process that O₂ undergoes dissociative adsorption onto the parent [Formula: see text] clusters is exothermic; (3) [Formula: see text] isomers show smaller X-A energy gaps than those of parent [Formula: see text] clusters, reflecting that their geometric and electronic structures are distorted remarkably due to dissociative adsorption of O₂.

Adsorption of acetylsalicylic acid on the aluminum nitride nanotube in both gas and solvent medium: a DFT study

The adsorption of acetylsalicylic acid (ASA) on the outer surfaces of a (1 , 1) aluminum nitride single-wall nanotube (AlNNT) was studied by quantum chemical study calculation. The adsorption energy of ASA on the AlNNT surface was calculated about - 15.62 kcal/mol. The more negative adsorption energy is ascribed to the electrostatic interaction of ASA with AlNNT. By absorbing the aspirin drug on the surface of AlNNT, the nanotube electrical conductivity has increased dramatically by about 21.75%, which can be used as a drug detection signal. Based on the polarizable continuum model (PCM) calculation, the AlNNT-ASA complex in water medium is more stable compared with that in the gas medium. Finally, our findings also revealed that the AlNNT would selectively identify the ASA molecule in the presence of environmental pollutants.

Graphene-like boron carbide monolayer as an electronic and work function-type sensor for dopamine drug

The electronic response of both pristine and Al-doped BC₃ nanosheets toward 3, 4-dihydroxyphenyl ethylamine, i.e. dopamine (DA) was studied through density functional theory. Based on the adsorption energy the tendency of pristine BC₃ toward DA drug insignificant and also after adsorption of DA drug the electronic properties of BC₃ were changed negligibly. While doping the sheet by Al significantly increases its reactivity and sensitivity toward the DA drug. By adsorption of DA HOMO-LUMO gap dramatically decreased of from 1.34 to 1.12 eV, thereby enhancing the electrical conductivity. It indicates that the doped BC₃ nanosheets may be a suitable candidate as a DA electronic sensor, unlike the pristine BC₃. Furthermore, the work function of doped BC₃ was changed significantly after DA adsorption. Based on these results the doped BC₃ can also act as a work function-type sensor to the sensing of DA was used. Finally, the most important factor of the doped BC₃ sheet is a short recovery time of 7.36 ms for the desorption process of DA.

Modelling the adsorption of natural organic matter on Ag (111) surface: Insights from dispersion corrected density functional theory calculations

Understanding the nature of the interactions between natural organic matter (NOM) and engineered nanoparticles (ENPs) is of crucial importance in understanding the fate and behaviour of engineered nanoparticles in the environment. In the present study, dispersion-corrected density functional theory (DFT-D) has been used to elucidate the molecule-surface interactions of higher molecular weight (HMW) NOM ambiguously present in the aquatic systems, namely: humic acid (HA), fulvic acid (FA) and protein Cryptochrome (Cry) on Ag (111) surface. Investigations were done in the gas phase and to mimic real biological environment, water has been used as a solvent within the conductor-like screening model (COSMO) framework. The calculated adsorption energies for HA, FA and Cry on Ag (111) surface were -27.90 (-18.45) kcal/mol, -38.28 (-18.68) kcal/mol and -143.89 (-150.82) kcal/mol respectively in the gas (solvent) phase and the equilibrium distances between the surface and HA, FA and Cry molecules were 1.87 (2.18) Å, 2.31(2.31) Å and 1.91 (1.70) Å respectively in the gas (solvent) phase. In both gas and water phase Cry showed stronger adsorption which means it has a stronger interaction with Ag (111) surface compared to HA and FA. The results for adsorption energy, solvation energy, isosurface of charge deformation difference, total density of state and partial density of states indicated that indeed these chosen adsorbates do interact with the surface and are favourable on Ag (111) surface. In terms of charge transfer, one of many calculated descriptors in this study, electrophilicity (ω) concur that charge transfer will take place from the adsorbates to Ag (111) surface.

Adsorption Behavior of CH4 Gas Molecule on the MoX2(S, Se, Te) Monolayer: The DFT Study

We predict the CH₄-sensing performance of monolayer MoX₂(S, Se, Te) with X-vacancy, Mo-vacancy, and divacancy by the density functional theory (DFT). The results demonstrate that the combination of different sixth main group elements with Mo atom has different adsorption behaviors for CH₄ gas molecule. Compared with MoX₂, MV_X, MV_Mo, and MV_D generally exhibit better adsorption properties under the same conditions. In addition, different defects will have different effects on adsorption behavior of the systems, the MV_D(MoTe₂) has the better adsorption, the better charge transfer, and the shortest distance in these systems. The results are proposed to predict the CH₄ gas molecule adsorption properties of MV_D(MoTe₂) and would help in guiding experimentalists to develop better materials based on MoX₂ for efficient gas detection or sensing applications.

MD simulation of methane adsorption properties on pillared graphene bubble models

Pillared graphene bubble framework is selected as the methane storage vessel in this article. All investigations of methane adsorption are executed by using the MD simulations. The average adsorption energy of methane on different bubble models is between - 4.3 and - 5.2 kcal/mol, which is desirable for absorbing and desorbing gas molecules. The methane adsorption properties of bubble models are obviously different from those of pillared graphene. The effect of graphene interlayer spacing on methane adsorption in selected bubble models can be negligible. Nevertheless, bubble density and temperature have a significant influence on methane adsorption. The amount of adsorbed methane on pillared bubble models at room temperature can reach up to 18.2 mmol/g. This performance of methane adsorption on pillared graphene bubble structures may bring new enlightenment to the investigations of gas storage materials.

Structure and crystal phase transition effect of Sn doping on anatase TiO2 for dichloromethane decomposition

Efficient removal of chlorinated volatile organic compounds (CVOCs) has received great attention because of the considerable harm that they cause to the environment and to human health. Developing novel catalysts and exploring the catalytic activation and deconstruction mechanism of CVOCs molecule are always the focus in this field. Here, a set of Sn doped TiO₂ catalysts were investigated for the decomposition of dichloromethane (DCM). Rietveld refinement of the XRD patterns showed that Sn ions can uniformly disperse into TiO₂ and induce the crystal transition of anatase. Meanwhile, such decorating can induce an increase in specific surface area and affect the surface oxygen vacancy concentration of these samples, which have been demonstrated by N₂ adsorption and XPS, respectively. Catalytic performance tests indicated that the Sn_0.2Ti_0.8O₂ has the best activity for DCM decomposition, and a lower CH₃Cl selectivity than that of pure TiO₂. Computational results suggested the dominant surface (110) of rutile Sn_0.2Ti_0.8O₂ is more beneficial for the adsorption/dissociation of DCM molecule than that of anatase TiO₂ (101). That's because the anchoring of DCM to Sn sites and electron enrichment on the surface bridge oxygen atoms of rutile Sn_0.2Ti_0.8O₂ (110) can promote the nucleophilic substitution process for breaking of CCl bonds.

Boron decorated graphene nanosheet as an ultrasensitive sensor: the role of coverage

The gas sensing performance of graphene could be unusually improved by decoration of various atoms on its sheet based on experimental and theoretical calculations. Considering that, as yet, experimental development on boron decorated graphene (BG) is still very rare; in this investigation, we used first-principle calculations to study the electrochemical properties of pure graphene (PG) in addition to various coverages of BG upon adsorption of CO as a lethal gas. We observe stronger adsorption as well as higher charge transfer in terms of increasing the B-coverage (Θ) from CO to graphene. Moreover, adsorption energies are scaled substantially by the rate of coverage attributed to the role of co-adsorption. We also find that all adsorption sites for boron on the graphene substrate lead to the same values at high coverage limit. Our results confirm experimental data on the enhanced gas sensitivity of boron-doped graphene and show that B-decorated manipulation of the graphene layer is potentially very favorable for designing new sensors for toxic gas detection.

The Potential Application of BAs for a Gas Sensor for Detecting SO2 Gas Molecule: a DFT Study

Different atmospheric gas molecules (e.g., N2, O2, CO2, H2O, CO, NO, NO2, NH3, and SO2) are absorbed on the pristine hexagonal boron arsenide (BAs) through density functional theory calculations. For each gas molecules, various adsorption positions were considered. The most stable adsorption depended on position, adsorption energy, charge transfer, and work function. SO2 gas molecules had the best adsorption energy, the shortest distance for BAs surface in the atmospheric gas molecule, and a certain amount of charge transfer. The calculation of work function was important for exploring the possibilities of adjusting the electronic and optical properties. Our results presented BAs materials can be the potential gas sensor of SO2 with high sensitivity and selectivity.

Graphene oxide reinforced ionic liquid-functionalized adsorbent for solid-phase extraction of phenolic acids

An environmental friendly sorbent of polymeric ionic liquids modified graphene oxide-grafted silica (PILs@GO@Sil) was synthesized for solid-phase extraction (SPE) of phenolic acids. The sorbent was prepared via a chemical layer-to-layer fabrication including amidation reaction, surface radical chain-transfer polymerization and in situ anion exchange. After modification with PILs, the silica surface had higher positive potential so that it would exhibit stronger electrostatic interaction for acidic compounds compared with GO@Sil. The adsorption performance of phenolic acids was investigated through the theoretical calculation and static, kinetic state adsorption experiments. Under the optimized conditions, wide linear ranges were obtained with correlation coefficients ranging from 0.9912 to 0.9998, and limits of detection were in the range of 0.20-0.50μgL^-1. Compared with other reported methods, the proposed PILs@GO@Sil-SPE-HPLC showed higher extraction efficiency. Finally, the black wolfberry yogurt and urine were analyzed as real samples and good recoveries spiked with standard solution were obtained.

Electronic properties and gas adsorption behaviour of pristine, silicon-, and boron-doped (8, 0) single-walled carbon nanotube: A first principles study

Carbon nanotubes (CNTs) have received enormous attention due to their fascinating properties to be used in various applications including electronics, sensing, energy storage and conversion. The first principles calculations within density functional theory (DFT) have been carried out in order to investigate the structural, electronic and optical properties of un-doped and doped CNT nanostructures. O₂, CO₂, and CH₃OH have been chosen as gas molecules to study the adsorption properties based on zigzag (8,0) SWCNTs. The results demonstrate that the adsorption of O₂, CO_2, and CH₃OH gas molecules on pristine, Si-doped and B-doped SWCNTs are either physisorption or chemisorption. Moreover, the electronic properties indicating SWCNT shows significant improvement toward gas adsorption which provides the impact of selecting the best gas sensor materials towards detecting gas molecule. Therefore, these pristine, Si-, and B-doped SWCNTs can be considered to be very good potential candidates for sensing application.