Adsorption Of Single Atoms Research Articles

Selective Single-Atom Adsorption for Precision Separation of Lead Ions in Tap Water via Capacitive Deionization

Capacitive deionization (CDI) offers a cost-effective and low-energy method for selective removal of Pb2+ from drinking water. Modifying CDI electrode surfaces with functional groups presents a versatile approach to enhancing selective ion adsorption capacity. However, a comprehensive understanding of the selectivity and removal efficiency of Pb2+ among diverse functional groups remains unexplored. Here, we investigated the effects of different functional groups (-SH, -COOH, and -NH2) attached to the graphene oxide (GO) electrode surfaces on Pb2+ selectivity and removal efficiency. Surprisingly, GO-COOH demonstrated single-atom adsorption of Pb2+, displaying superior removal efficiency and selectivity compared with -SH and -NH2, although -SH possesses significant chelation capability for Pb2+. Both density functional theory (DFT) calculations and X-ray pair distribution function (PDF) analyses confirmed that Pb2+ exhibits a theoretically higher affinity to -COOH. This research deepens our understanding of the interactions between functional groups and heavy metal ions, enabling selective and rapid separation of target cations for water purification.

Effects of Alloying Element on Hydrogen Adsorption and Diffusion on α-Fe(110) Surfaces: First Principles Study

Based on first principles density functional theory (DFT) methods, this study employed the Cambridge Serial Total Energy Package (CASTEP) module within Materials Studio (MS) software under the generalized gradient approximation to investigate the adsorption, diffusion behavior, and electronic properties of hydrogen atoms on α-Fe(110) and α-Fe(110)-Me (Mn, Cr, Ni, Mo) surfaces, including calculations of their adsorption energies and density of states (DOS). The results demonstrated that doping with alloy atoms Me increased the physical adsorption energy of H2 molecules on the surface. Specifically, Mo doping elevated the adsorption energy from −1.00825 eV to −0.70226 eV, with the largest relative change being 30.35%. After doping with Me, the chemical adsorption energy of two hydrogen atoms does not change significantly, among which doping with Cr results in a decrease in the chemical adsorption energy. Building on this, further analysis of the chemical adsorption of single atoms on the surface was conducted. By comparing the adsorption energy and the bond length between a hydrogen atom and iron/dopant metal atom, it was found that Mo doping has the greatest impact, increasing the bond length by 58.58%. Analysis of the DOS functions under different doping conditions validated the interaction between different alloy elements and H atoms. Simultaneously, simulations were carried out on the energy barrier crossed by H atoms diffusing into the metal interior. The results indicate that Ni doping facilitates the diffusion of H atoms, while Cr, Mn, and Mo hinder their diffusion, with Mo having the most significant effect, where its barrier is 21.88 times that of the undoped surface. This conclusion offers deep insights into the impact of different doping elements on hydrogen adsorption and diffusion, aiding in the design of materials resistant to hydrogen embrittlement.

Investigating the dilute magnetic semiconductor behavior of 4d transition metal adsorption on B4C3

We conducted a systematic investigation of B4C3 adsorbed with 4d-transition metals (4d-TMs), including Tc, Cd, Mo, Nb, Rh, Ru, and Ag, using first principles. This study involved an evaluation of structural, electronic, and magnetic properties. When single atom adsorption was adsorbed to B4C3 using elements such as Tc, Nb, Rh, Ru, and Ag, it demonstrated characteristics of a diluted magnetic semiconductor (DMS), manifesting magnetic moments. Conversely, Cd, Mo, and Pd exhibited behavior consistent with non-magnetic semiconductors. Ferromagnetic (FM) and antiferromagnetic (AFM) arrangements were formed through the adsorption of 2TM atoms on B4C3. In the FM setup, Ru and Nb uphold their roles as DMS. Interestingly, Tc and Rh exhibit half-metal behavior in this configuration, displaying their potential utility in spintronics applications. In the AFM configuration, Tc displayed half-metallic behavior, while the other metals maintained the same characteristics observed in the case of single TM adsorption. The reactivity of Nb-B4C3 is notably high owing to its low work function, whereas Cd-B4C3 is observed to be less reactive. AFM coupling is favorable in the 2Nb-, 2Rh-, and 2Ru-B4C3 systems, while 2Tc-B4C3 displays FM coupling. Transition metals belonging to the 4d series hold the potential to enhance the properties of B4C3, including its half-metallic, metallic, and semiconductor characteristics. These findings suggest the potential use of 4D transition metals adsorbed on B4C3 as a prospective material for spintronics and magnetic storage applications in the future.

Defect Engineering Promoted Ultrafine Ir Nanoparticle Growth and Sr Single‐Atom Adsorption on TiO2 Nanowires to Achieve High‐Performance Overall Water Splitting in Acidic Media

AbstractThis work reports the use of the metal‐support interaction strengthening through defect engineering and single atom adsorption to the supports to increase the catalytic activities of metals. Specifically, the plasma treated TiO2 nanowires with the Ir nanoparticle growth and the Sr single atom adsorption (the Ir@Sr‐p‐TiO2 NWs) are synthesized and demonstrated to be efficient catalysts for OER and HER. They only need overpotentials of 250 and 32 mV to drive 10 mA cm−2 for OER and HER, respectively. Their OER and HER activities are much higher than the commercial IrO2 and Pt/C. The high activities of the Ir@Sr‐p‐TiO2 NWs mainly arise from the strengthened metal‐support interactions between the Ir nanoparticles and the p‐TiO2 NWs, achieved by the plasma generated oxygen defects (Vo·) and the Sr adsorption on the p‐TiO2 NWs. Analysis and DFT calculations indicate that the Vo· and Sr adsorption can promote the charge transfer from the p‐TiO2 NWs to the Ir nanoparticles, optimizing the adsorptions of the OER and HER intermediates on the O‐ and H‐covered Ir nanoparticles. Additionally, the strong metal‐support interactions can increase the stabilities of the Ir NPs against the chemical corrosions, increasing the OER and HER durabilities of the Ir@Sr‐p‐TiO2 NWs.

Multiferroicity driven by single-atom adsorption on the two-dimensional semiconductor ScCl3.

In recent years, two-dimensional (2D) transition metal halides (such as CrI3) have received more and more attention for the practical applications of spintronic devices due to their unique electronic and magnetic properties. However, most 2D transition metal halides are centrosymmetric and are non-polar, which hinders their applications on nonvolatile memories. Here, on the basis of first-principles calculations, we predict that the adsorption of K single-atoms on the ScCl3 monolayer (denoted as K@ScCl3) could break the structural centrosymmetry and induce a reversible large out-of-plane electric polarization. Simultaneously, the adsorption of K single-atoms induces a magnetic moment localized on Sc ions, which forms a ferromagnetic order with an estimated Curie temperature of ∼37 K. These make the K@ScCl3 monolayer a ferromagnetic ferroelectric semiconductor. These findings propose a new route to realize 2D multiferroic materials, which is of great significance for the research and development of spintronics.

Adsorption and modification behavior of single atoms on the surface of single vacancy graphene: Machine learning accelerated first principle computations

During the preparation or processing of graphene, the emergence of structural flaws is an unavoidable circumstance, and these structural defects present a detrimental impact on the mechanical properties of graphene and its corresponding composite materials. In this paper, we use a first-principles computation to compute single-atom adsorption behavior on single vacancy graphene, from which adsorption energy and distance values are derived to create a dataset for machine learning. The comparative analysis of different machine learning models reveals that the BPNN model is best suited for the dataset. The BPNN model is enhanced by adjusting its node parameters using genetic algorithm, increasing its coefficient of determination to 0.9874 and 0.9608 for adsorption energy and distance models, respectively. The enhanced GA-BPNN model is utilized to predict the adsorption behavior of atoms across the entire periodic table onto single vacancy graphene’s surface. The accuracy of the machine learning model predictions is validated through the application of elemental modifications to the graphene. Employing machine learning to expedite first-principles calculations broadens the spectrum of available research approaches while accelerating the atomic modification process of single vacancy graphene. Our results provide valuable insights into the adsorption behavior of atoms on graphene surfaces and demonstrate the potential of machine learning for accelerating first principle computations in material science.

Two-Dimensional Ferroelectricity in a Single-Atom Adsorbed BiI3 Monolayer

Two-dimensional (2D) ferroelectric materials have received tremendous attention in recent years for their potential applications in high-performance electronic nanodevices, such as ferroelectric random-access memories. To increase the density of a ferroelectric memory, a 2D ferroelectric material with multiple ferroelectric states controllable via an external electric field is needed. However, 2D ferroelectric materials are still rare and most of them only have two equivalent ferroelectric states with opposite electric polarization directions. Here, we propose that a 2D ferroelectric material with multiple ferroelectric states can be realized by single-atom adsorption on a metal halide monolayer. Using first-principles calculations, we demonstrate that the 2D BiI3 monolayer adsorbed by Pd single atoms (denoted as Pd@BiI3) is a stable ferroelectric material, which possesses six equivalent ferroelectric states with different electric polarization directions. These findings provide a potential route to achieve multi-state 2D ferroelectric materials for multi-functional device applications.

Spatial Differentiation of Aluminium Siting by the Single-Atom Adsorption Sites in Zeolite by Electron Microscopy

Spatial Differentiation of Aluminium Siting by the Single-Atom Adsorption Sites in Zeolite by Electron Microscopy

Study of Cu, Co and Ru Nanoclusters on MoS2 to Predict Thin Film Morphology

Interfaces of 2D materials with metals are of interest for a large variety of applications, including sensors, batteries, catalysis, electronics, and semi-conductor devices. Transition metal dichalcogenides (TMDs) and specifically MoS2 are some of the most widely studied 2D materials. A detailed understanding of the interactions of metals with 2D TMDs can give useful insights into possible applications for metal-TMD systems. However, the literature focuses mainly on comparing trends in single atom adsorption and studying nanoparticles on MoS2 monolayers.In this work we aim to increase the understanding of metal-MoS2 interactions and metal nucleation on TMDs. We use density functional theory (DFT) to study the adsorption of small metal clusters with up to four atoms on MoS2 monolayers. Insights gained from this work allow us to understand the initial nucleation of metal thin films on TMDs as well as predict the likely morphology of the thin film as it grows.The metals studied are Cu, Co and Ru, which are chosen for their range of applications, particularly in electronics. Metal-substrate interactions, preferred adsorption modes and stable nanocluster geometries are presented on pristine MoS2 and in the presence of the readily formed sulfur vacancy. The strength of interaction between the metals and MoS2 is in the order Co > Ru > Cu. Metal-substrate interactions are localised to the adsorption site; however we find that both Ru and Co can induce formation of sulfur vacancies through the formation of the corresponding metal sulfide.

Manipulation of CO adsorption over Me1/CeO2 by heterocation doping: Key roles of single-atom adsorption energy.

The performance of metal atoms chemically bonded to oxide supports cannot be explained solely by the intrinsic properties of the metals such as the d-band center. Herein, we present an in-depth study of the correlation between metal-oxide interactions and the properties of the supported metal using CO adsorption on Me1 (Fe1, Co1, and Ni1) loaded over CeO2 (111) doped with divalent (Ca, Sr, and Ba), trivalent (Al, Ga, Sc, Y, and La), and quadrivalent (Hf and Zr) heterocations. CO adsorption over Me1 is strongly dependent on the binding energies of Me1. Two factors led to this trend. First, the extent of the Me1-surface oxygen (Me1-O) bond relaxation during CO adsorption played a key role. Second, the d-band center shifted drastically because of charge transfer to the oxides. The shift is related to the oxophilicity of metals. Adsorption energies of Me1 over oxides include the contributions of the factors described above. Therefore, we can predict the activities of Me1 using the strength of anchoring by oxide supports. Results show that smaller ionic radii of the doped heterocations were associated with more tightly bound Me1. This finding sheds light on the possibility of heterocation-doping manipulating the reactivity of the Me1 catalyst based on theoretical predictions.

Single atom transition metals on MoS2 monolayer and their use as catalysts for CO2 activation

The properties of single metal atoms adsorbed on MoS2 monolayer surface as well as the behaviour of CO2 molecules on these active sites are studied by using density functional theory methods. Eleven different transition metals (Au, Co, Cr, Cu, Fe, Ir, Mn, Ni, Pd, Pt or Sn) were considered as well as the main adsorption sites on the surface. Reported results show adsorption on top of Mo atoms and hollow sites on the hexagonal ring centres leading to very large adsorption energies. The adsorption is characterized by deep interaction wells and adsorbed metal to surface charge transfer in most of the studied atoms. The low surface coverage upon single atom adsorption hinders in plane metal diffusion and thus once atoms are adsorbed, they remain on top on each site as showed by Ab initio molecular dynamics simulations. The behaviour of CO2 molecules on top of active sites formed by metal atoms adsorbed on the monolayer is characterized by strong chemisorption, leading to large bending of gas molecules, thus showing how CO2 molecules can react on these metal sites. This work reports for the first time a systematic evaluation of transition metal atoms adsorbed on MoS2 monolayers, including their dynamic properties, as well as their properties as active sites for CO2 reactions.

Structure and Stability of Cun Clusters (n = 1-4) Adsorbed on Stoichiometric and Defective 2D MoS2

Layered materials, such as MoS2, are being intensely studied due to their interesting properties and wide variety of potential applications. These materials are also interesting as supports for low dimensional metals for catalysis, while recent work has shown increased interest in using 2D materials in the electronics industry as a Cu diffusion barrier in semiconductor device interconnects. The interaction between different metal structures and MoS2 monolayers is therefore of significant importance and first principle simulations can probe aspects of this interaction not easily accessible to experiment. Previous theoretical studies have focused particularly on the adsorption of a range of metallic elements, including first row transition metals, as well as Ag and Au. However, most studies have examined single atom adsorption or adsorb nanoparticles of noble metals. This means there is a knowledge gap in terms of thin film nucleation on 2D materials. To begin addressing this issue, we present in this paper a first principles density functional theory (DFT) study of the adsorption of small Cun structures, where n = 1-4, on 2D MoS2 as a model system. We find on a perfect MoS2 monolayer that a single Cu atom prefers an adsorption site above the Mo atom. With increasing nanocluster size the nanocluster binds more strongly when Cu atoms adsorb atop the S atom. Stability is driven by the number of Cu-Cu interactions and the distance between adsorption sites, with no obvious preference towards 2D or 3D structures. The introduction of a single S vacancy in the monolayer enhances copper binding energy, although some Cun nanoclusters are actually unstable. The effect of the vacancy is localised around the vacancy site. Finally on both the pristine and defective MoS2 monolayer, the density of states analysis shows that the adsorption of Cu introduces new electronic states as a result of partial Cu oxidation, but the metallic character of Cu nanoclusters is preserved.

DFT calculations of the structure and stability of copper clusters on MoS2.

Layered materials, such as MoS2, are being intensely studied due to their interesting properties and wide variety of potential applications. These materials are also interesting as supports for low-dimensional metals for catalysis, while recent work has shown increased interest in using 2D materials in the electronics industry as a Cu diffusion barrier in semiconductor device interconnects. The interaction between different metal structures and MoS2 monolayers is therefore of significant importance and first-principles simulations can probe aspects of this interaction not easily accessible to experiment. Previous theoretical studies have focused particularly on the adsorption of a range of metallic elements, including first-row transition metals, as well as Ag and Au. However, most studies have examined single-atom adsorption or adsorbed nanoparticles of noble metals. This means there is a knowledge gap in terms of thin film nucleation on 2D materials. To begin addressing this issue, we present in this paper a first-principles density functional theory (DFT) study of the adsorption of small Cun (n = 1–4) structures on 2D MoS2 as a model system. We find on a perfect MoS2 monolayer that a single Cu atom prefers an adsorption site above the Mo atom. With increasing nanocluster size the nanocluster binds more strongly when Cu atoms adsorb atop the S atoms. Stability is driven by the number of Cu–Cu interactions and the distance between adsorption sites, with no obvious preference towards 2D or 3D structures. The introduction of a single S vacancy in the monolayer enhances the copper binding energy, although some Cun nanoclusters are actually unstable. The effect of the vacancy is localised around the vacancy site. Finally, on both the pristine and the defective MoS2 monolayer, the density-of-states analysis shows that the adsorption of Cu introduces new electronic states as a result of partial Cu oxidation, but the metallic character of Cu nanoclusters is preserved.

Platinum single-atom adsorption on graphene: a density functional theory study.

Single-atom catalysis, which utilizes single atoms as active sites, is one of the most promising ways to enhance the catalytic activity and to reduce the amount of precious metals used. Platinum atoms deposited on graphene are reported to show enhanced catalytic activity for some chemical reactions, e.g. methanol oxidation in direct methanol fuel cells. However, the precise atomic structure, the key to understand the origin of the improved catalytic activity, is yet to be clarified. Here, we present a computational study to investigate the structure of platinum adsorbed on graphene with special emphasis on the edges of graphene nanoribbons. By means of density functional theory based thermodynamics, we find that single platinum atoms preferentially adsorb on the substitutional carbon sites at the hydrogen terminated graphene edge. The structures are further corroborated by the core level shift calculations. Large positive core level shifts indicate the strong interaction between single Pt atoms and graphene. The atomistic insight obtained in this study will be a basis for further investigation of the activity of single-atom catalysts based on platinum and graphene related materials.

Functionalization Ti3C2 MXene by the adsorption or substitution of single metal atom

Chemical modification of MXenes, as an effective strategy to improve the electronic harmony with other materials, paves huge impetus to their practically industrial application. In this study, by means of Density Functional Theory (DFT) calculations, the adsorption and substitution of single transition metal atoms (M = 3d (Fe, Co, Ni, Cu, Zn), 4d (Ru, Rh, Pd, Ag, Cd), 5d (Os, Ir, Pt, Au, Hg)) on Ti3C2 MXene have been systematically investigated. It is found that the adsorption (adsorption energies Ead = −1.05 ∼ −7.98 eV) of single metal atoms on Ti3C2 are much stronger than those on graphene and graphyne. Interestingly, via a series of electronical structure calculations, we found good linear correlation between Ead and chemically properties (such as the average bond distances dM-Ti, the bader charge and the d-electron centre of metal), shedding light on the harmonic effect of doping metals both electronical and geometrically. In other words, the stronger adsorption, shorter bond distance, more bader charge, less negative d-electron centre. While for the substitution of single metal atom on Ti3C2, a linear relationship is also found except that the volcano curve are formed between the substitution energies and bader charges. Moreover, the charge transfer decrease firstly and then increase in both first and third layer. Generally, single-atom adsorption or substitution is a feasible method to improve the functionalization Ti3C2 MXene.

The possible magnetoelectric coupling induced by adsorption in SnTe films

Abstract Based on the recent discovery of the stable in-plane spontaneous polarization in SnTe films. We report the possible magnetoelectric (ME) coupling induced by adsorption in SnTe films by performing density functional calculations. Firstly, we investigate the adsorption-induced magnetic behaviors on the two-dimensional SnTe monolayer. Five kinds of adatoms (H, B, C, N and O) are taken into account. It is found that the SnTe with adsorbing H and B have nonzero magnetic moments and good stability. Secondly, the coexistence of the ferromagnetism and ferroelectrics (i.e. multiferroics) is observed in H-adsorbed SnTe. The magnetoelectric coupling in this system is studied by calculating the poralazition in different magnetic structures (antiferromagnetic and ferroelectric). According to our study, we propose that it is a possible method obtaining the multiferroicity and ME coupling to modify the SnTe films by chemical adsorption of single atoms.

Theoretical study of carbon-based tips for scanning tunnelling microscopy

Motivated by recent experiments, we present here a detailed theoretical analysis of the use of carbon-based conductive tips in scanning tunnelling microscopy. In particular, we employ ab initio methods based on density functional theory to explore a graphitic, an amorphous carbon and two diamond-like tips for imaging with a scanning tunnelling microscope (STM), and we compare them with standard metallic tips made of gold and tungsten. We investigate the performance of these tips in terms of the corrugation of the STM images acquired when scanning a single graphene sheet. Moreover, we analyse the impact of the tip-sample distance and show that it plays a fundamental role in the resolution and symmetry of the STM images. We also explore in depth how the adsorption of single atoms and molecules in the tip apexes modifies the STM images and demonstrate that, in general, it leads to an improved image resolution. The ensemble of our results provides strong evidence that carbon-based tips can significantly improve the resolution of STM images, as compared to more standard metallic tips, which may open a new line of research in scanning tunnelling microscopy.

A computational study of Na behavior on graphene

We present the first ab initio and molecular dynamics study of Na adsorption and diffusion on ideal graphene that considers Na–Na interaction and dispersion forces. From density functional theory (DFT) calculations using the generalized gradient approximation (GGA), the binding energy (vs. the vacuum reference state) of −0.75eV is higher than the cohesive energy of Na metal (EcohDFT=−1.07 eV). The binding energy approaches the Na metal cohesive energy (EcohDFT−D=−1.21 eV) when dispersion correction is included (DFT-D), with Eb=−1.14eV. Both DFT and DFT-D predict that the increase of Na concentration on graphene results in formation of Na complexes. This is evidenced by smaller Bader charge on Na atoms of Na dimer, 0.55e (0.48e for DFT) compared to 0.86e (for both DFT and DFT-D) for the single atom adsorption as well as by the formation of a NaNa bond identified by analysis of the electron density. These results suggest that ideal graphene is not a promising anode material for Na-ion batteries. Analysis of diffusion pathways for a Na dimer shows that the dimer remains stable during the diffusion, and computed migration barriers are significantly lower for the dimer than that for the single atom diffusion. This indicates that Na–Na interaction should be taken into account during the analysis of Na transport on graphene. Finally, we show that the typical defects (vacancy and divacancy) induce significant strengthening of the NaC interaction. In particular, the largest change to the interaction is computed for vacancy-defected graphene, where the found lowest binding energy (vs. the metal reference state) is about 1.15eV (1.21eV for DFT) lower than that for ideal graphene.

First-principles study of single atom adsorption on capped single-walled carbon nanotubes

The effects of hydrogen, oxygen, and nitrogen atomic chemisorption on capped armchair (5, 5) single-walled carbon nanotubes (SWCNT) are investigated by first-principles calculations based on the density functional theory aimed at the CNT based fuel cell applications. O or N chemisorption could break C–C bond to form doping type structure. C–C bonds are weakened from H chemisorption, favoring hydrogen storage. Both C–adatom and related C–C bond lengths fluctuate from the cap top to the tube for each type of adsorbate. There is a total amount of about 1.0 e charge transfer between N or O atom and the carbon atoms, and the catalytic activity is expected to be higher with N adsorption around the cap top. The adsorption energies and work functions also vary with the adsorption at different sites. Atomic chemisorptions are more stable on the cap than on the tube due to smaller local curvature radius. The work functions increase to above 5.0 eV with the adsorption of N and O, and drop below 4.8 eV for H adsorption, comparing with 4.89 eV for the clean tube. DOS study reveals orbital information for electrons of adatom contributed to the valence bands and the conduction bands.

Evolution of Pt Nanoparticles Supported on Fishbone-Type Carbon Nanofibers with Cone–Helix Structures: A Molecular Dynamics Study

Molecular dynamics simulations based on a reactive force field (ReaxFF) are performed to examine the effects of the variable morphologies of fishbone-type carbon nanofibers (f-CNFs) on the microstructures of supported Pt100 clusters. Four f-CNF cone–helix models with different basal-to-edge surface area ratios and edge plane terminations are employed. Calculated results indicate upon adsorption of Pt100 clusters a fraction of Pt atoms migrates from the metal particles onto the f-CNFs either to accumulate at the metal–support interface or to attain a single atom adsorption on the supports. With decreasing apex angle or introduction of H termination, the Pt atoms are more likely to be coordinated to the basal planes and the binding energies of the Pt100 clusters to the f-CNFs are lowered, accompanied by a lower degree of the cluster reconstruction. On the contrary, if more f-CNF edge planes are exposed, a higher Pt dispersion, lower surface first-shell Pt–Pt coordination numbers, and longer Pt–Pt surface bonds are attained. Considering the interplay between the geometric and the electronic structures of transition metal surfaces, the relationship among the support morphologies, the metal–support interactions, and the catalytic properties of the active Pt clusters is eventually elucidated.