Adjacent Atoms Research Articles

Adjacent atomic cobalt sites anchored on carbon foam as a self-supporting electrode for efficient hydrogen evolution

Based on the MOF derivation strategy of inkjet printing, carbon foam supported Co–N single atom catalysts was synthesized, which formed adjacent but dispersed Co single atom sites to promote hydrogen evolution.

Nonvolatile magnetoelectric coupling in two-dimensional van der Waals sandwich heterostructure CuInP2S6/MnCl3/CuInP2S6.

Electrical control of magnetism is of great interest for low-energy-consumption spintronic applications. Due to the recent experimental breakthrough in two-dimensional materials, with the absence of hanging bonds on the surface and strong tolerance for lattice mismatch, heterogeneous integration of different two-dimensional materials provides a new opportunity for coupling between different physical properties. Here, we report the realization of nonvolatile magnetoelectric coupling in vdW sandwich heterostructure CuInP2S6/MnCl3/CuInP2S6. Using first-principles calculations, we reveal that when interfacing with ferroelectric CuInP2S6, the Dirac half-metallic state of monolayer MnCl3 will be destroyed. Moreover, depending on the electrically polarized direction of CuInP2S6, MnCl3 can be a half-metal or a ferromagnetic semiconductor. We unveil that the obtained ferromagnetic semiconductor in MnCl3 can be attributed to the different gain and loss of electrons on the two adjacent Mn atoms due to the sublattice symmetry broken by interlayer coupling. The effects of interfacial magnetoelectric coupling on magnetic anisotropy and ferromagnetic Curie temperature of MnCl3 are also investigated, and a multiferroic memory based on this model is designed. Our work not only provides a promising way to design nonvolatile electrical control of magnetism but also renders monolayer MnCl3 an appealing platform for developing low-dimensional memory devices.

Aminals as powerful XAT-reagents: activation of fluorinated alkyl chlorides.

Readily available 1,3,5-trimethyl-1,3,5-triazinane serves as an efficient reagent for halogen atom transfer. Under photocatalytic conditions, the triazinane generates an α-aminoalkyl radical, which can activate the C-Cl bond of fluorinated alkyl chlorides. The hydrofluoroalkylation reaction between fluorinated alkyl chlorides and alkenes is described. The efficiency of the diamino-substituted radical derived from the triazinane is associated with stereoelectronic effects defined by a six-membered cycle forcing the anti-periplanar arrangement of the radical orbital and lone pairs of adjacent nitrogen atoms.

Activating lattice oxygen of single-layer ZnO for the catalytic oxidation reaction.

Tuning an oxide/metal interface is of critical importance for the performance enhancement of many heterogeneous catalytic reactions. However, catalytic oxidation occurring at the interface between non-reducible oxide and metal has been challenging, since non-reducible oxides hardly lose their lattice oxygen (OL) or dissociate O2 from the gas phase. In this work, a ZnO monolayer film on Au(111) is used as an inverse catalyst to investigate CO oxidation occurring at the ZnO/Au(111) interface via high pressure scanning tunneling microscopy. Surface science experiments indicate that oxygen intercalation under the ZnO monolayer film, termed ZnO/O/Au(111), can be achieved via a surface reaction with 1 × 10-6 mbar O3. Subsequent exposure of the formed ZnO/O/Au(111) surface to mbar CO at room temperature leads to the recovery of the pristine ZnO/Au(111) surface. Theoretical calculations reveal that OL adjacent to intercalated oxygen (Oint) is activated due to the OL-Zn-Oint bonding and surface corrugation, which can be directly involved in CO oxidation. Subsequently, Oint migrates to the formed oxygen vacancy from the subsurface resuming the pristine ZnO structure. These results thus reveal that oxygen intercalation underneath single-layer ZnO will strongly boost the oxidation reaction via activating adjacent lattice oxygen atoms.

Pillar-layer Zn-triazolate-dicarboxylate frameworks with a customized pore structure for efficient ethylene purification from ethylene/ethane/acetylene ternary mixtures.

The selective adsorption of C2H6 and C2H2 over C2H4 from C2H2/C2H4/C2H6 ternary mixtures for one-step C2H4 purification represents a crucial yet challenging task in industry. The pore structure of the adsorbents must be finely tailored to meet the demanding requirements for the separation considering the very similar physicochemical properties of the three gases. Herein, we report a Zn-triazolate-dicarboxylate framework, HIAM-210, featuring a novel topology which possesses one-dimensional channels decorated with adjacent uncoordinated carboxylate-O atoms. The suitable pore size and customized pore environment enable the compound to selectively capture C2H6 and C2H2 with high C2H2/C2H4 and C2H6/C2H4 selectivities of both 2.0. Breakthrough experiments show that polymer-grade C2H4 can be directly harvested from C2H2/C2H4/C2H6 (34/33/33 and 1/90/9) ternary mixtures. The underlying mechanism of the preferential adsorption was uncovered by grand canonical Monte Carlo simulations and DFT calculations.

Diatomic molecule catalysts toward synergistic electrocatalytic carbon dioxide reduction

The two adjacent Co atoms in the catalyst are 0.523 nm apart and could synergistically activate CO2 and H2O to form a hydrogen bond. Synergistic catalysis could promote CO2 activation, stabilize the intermediate, and decrease the energy barrier.

Conformational preference in difluoroacetamide oligomers: probing the potential for foldamers with C-H⋯O hydrogen bonds.

The C-H bond of a difluoroacetamide group, acidified by two adjacent fluorine atoms, could in principle provide conformational organisation for foldamers based on C-H⋯O hydrogen bonds. We find that in model oligomeric systems, this weak hydrogen bond leads only to partial organisation of the secondary structure, with the conformational preference of the difluoroacetamide groups being predominantly governed by dipole stabilisation.

Synthesis and structural analysis of tetranuclear Zn(II) complex with 2,3-dihydroxybenzaldehyde-aminoguanidine

Here we report a new Schiff base of aminoguanidine and 2,3-dihydroxybenzaldehyde (H2L) and its physicochemical characterization, along with an investigation into its coordination affinities towards zinc. By reacting zinc acetate with the chloride salt of the ligand in the MeCN?H2O solution, yellow single-crystals of tetranuclear, centrosymmetric complex, with the formula [Zn2(?-L)(?-OAc)2]2?2MeCN, were obtained. The complex was characterized by IR spectroscopy, conductometry, elemental analysis, and single-crystal X-ray diffraction analysis. Notably, both nitrogen atoms of the aminoguanidine residue coordinate to the same zinc atom, while both deprotonated phenyl oxygen atoms achieve bridging coordination. Furthermore, two acetate anions bridge adjacent zinc atoms in addition to the Schiff base anion. Meaningful insights into the hierarchy and significance of intermolecular interactions within the crystal structure were gained by estimating the energies using the CrystalExplorer model. The calculations revealed that the crystal structure can be classified as a layer type, with notably stronger interactions occurring along the [001] and [011] directions.

The effect of composition changes on the structure and electronic properties of jamesonite: a DFT study.

Models of jamesonite with different compositions were built by different amounts of Sb or Pb substitution at Fe sites, and their structures and electronic properties were studied using the DFT method. The structure and properties of jamesonite significantly changed after Sb or Pb substitution. The lengths of the Sb-S and Pb-S bonds are larger than those of the corresponding Fe-S bonds of pure jamesonite, and the polarization of iron atoms adjacent to substitute atoms is weakened. After one Sb atom substitution, the S atoms bonded to Sb (substitution atom) gain more charges than those before Sb substitution. The Sb atom has more positive charges than the corresponding Fe atom before Sb substitution. For one Pb substitution system, the electrons transfer from the substituted Pb to adjacent S atoms, and the larger negative charge of the S atoms causes a slightly stronger Pb-S bond. With increasing Sb or Pb content, the electronic structural changes of the adjacent atoms are similar to those of one Sb or Pb substitution. However, the increase of 4-coordination Sb or 4-coordination Pb with the decrease of Fe atom changes the electronic structure of jamesonite, which will change its flotation performance.

Modulating paired Ir-O-Ir via electronic perturbations of correlated Ir single atoms to overcome catalytic selectivity.

Single-atom catalysts have been extensively utilized for electrocatalysis, in which electronic metal-support interactions are typically employed to stabilize single atoms. However, this neglects the metal-metal interactions of adjacent atoms, which are essential for the fine-tuning of selective sites. Herein, the high-loading of Ir single atoms (Ir SAs) (8.9 wt%) were adjacently accommodated into oxygen vacancy-rich Co3O4 nanosheets (Ir SAs/Co3O4). Electronic perturbations for both Ir single atoms and Co3O4 supports were observed under electronic metal-support and metal-metal interactions, thus generating Ir-O-Co/Ir units. Electrons were transferred from Co and Ir to O atoms, inducing the depletion of 3d/5d states in Co/Ir and the occupation of 2p states in O atoms to stabilize the Ir SAs. Moreover, the O atoms of Ir-O-Ir functioned as the main active sites for the electrocatalysis of As(iii), which reduced the energy barrier for the rate-determining step. This was due to the stronger electronic affinities for intermediates from reduction of As(iii), which were completely distinct from other coordinated O atoms of Co3O4 or IrO2. Consequently, the resultant Ir SAs/Co3O4 exhibited far more robust electrocatalytic activities than IrO2/Co3O4 and Co3O4 in the electrocatalysis of As(iii). Moreover, there was a strong orbital coupling effect between the coordinated O atoms of Ir SAs and the -OH of H3AsO3, thus exhibiting superior selectivity for As(iii) in contrast to other common heavy metal cations. This work offers useful insights into the rational design of intriguing SACs with high selectivity and stability for the electrocatalysis and electrochemical analysis of pollutants on an electronic level.

A practical FeP nanoarrays electrocatalyst for efficient catalytic reduction of nitrite ions in wastewater to ammonia

Ammonia production is an energy-intensive process while nitrite ions are a substantial environmental pollutant, therefore the conversion of nitrite ions (NO2-) into ammonia (NH3) via an electrochemical process is of great significance. Using a hydrothermal method plus a low temperature phosphating process, iron phosphide nanoarrays (FeP NA) were prepared on a Ti plate to form FeP NA|Ti, which was then used to efficiently convert NO2- ions into NH3. In a single-chamber cell using a neutral pH electrolyte, the Faradaic efficiency for nitrite to ammonia conversion reached 82.5 ± 2.3 %. Various parameters were optimized to ensure the high performance of FeP NA|Ti which were explained with mechanistic studies. It was found that atomic hydrogen (H*) greatly impacts both the reaction rate and selectivity. Furthermore, density functional theory (DFT) calculations reveal that the (211) and (011) facets of FeP are the main active faces for nitrite reduction where the nitrite ions tend to bind with two adjacent Fe atoms of FeP to ensure maximum performance.

σ-Delocalization between Non-bonded Selenium Atoms on Multiply Se-substituted Benzenes

The delocalization arising from lone-pair interactions of non-bonded selenium atoms in multiply selenium-substituted benzenes is demonstrated. The first oxidation potentials of the compounds shift to a lower voltage as the number of adjacent selenium atoms increases from unity to six. The steric hindrance forces the selenium functionalities to produce σ-delocalization derived from interactions between lone-pair electrons of non-bonded selenium atoms.

N-doped coralline Co9S8−xNx for inducing Amitriptyline decontamination in Electro-Fenton Process: Degradation scheme Elucidation, nitrogen activating catalyst delocalized electron and enhancing 2-Electron oxygen reduction reaction mechanism investigation

Improving the recalcitrant emergent contaminant removal in electron-Fenton (EF) has been one of the focal problems. Here, a N-doped coralline Co9S8−xNx catalyst was synthesized with high electronegativity and strong spin polarization for promoting the H2O2 generation efficiency and Amitriptyline (AMT) removal. After doping nitrogen, catalytic performance of Co9S8−xNx has increased ∼10 % on AMT decay and the treatment time was shortened ∼40 min. Co9S8−xNx induced 2-electron oxygen reduction reaction (ORR) mechanism has also been investigated. According to electronic structure analysis, electrons surrounding the cobalt atoms were redistributed and the π* orbitals of *O2 were occupied asymmetrically forcing *O2 to be of radical nature active for hydrogenation, which significantly reduced required absorption energy in the rate-determining step (RDS). This work clarifies the mediate role of N-doped activating delocalized electron of adjacent atoms on the surface of Co9S8−xNx and also gives new insights into the rational design of catalyst for refractory pollutant degradation in wastewater.

Single Zinc Atom Aggregates: Synergetic Interaction to Boost Fast Polysulfide Conversion in Lithium-Sulfur Batteries.

Single-atom catalysts (SACs) pave new possibilities to improve the utilization efficiency of sulfur electrodes arising from polysulfide shuttle effects and sluggish kinetics due to their excellent applicability in atomic-scale reaction mechanisms and structure-activity relationships. Herein, nitrogen (N)-anchored SACs on the highly ordered N-doped carbon nanotube arrays are reported as the sulfur host for fast redox conversion in lithium-sulfur (Li-S) batteries. The cube structure of the aligned carbon nanotubes can promote the rapid mass transfer under high sulfur loadings, and abundant single-atom active sites further accelerate the conversion of lithium polysulfides (LiPSs). The synergistic enhancement effect induced by adjacent single atoms with interatomic distances <1nm further accelerates the rapid multi-step reaction of sulfur at high sulfur loadings. As a result, the obtained Li-S batteries exhibit outstanding cycle stability with a high areal capacity of 5.6mAhcm-2 after 100 cycles under a high sulfur loading of 7.2mgcm-2 (electrolyte to sulfur ratio is ≈3.7mLg-1 ). Even assembled into a pouch cell, it still delivers a high capacity of 953.4mAhg-1 after 100 cycles at 0.1C, contributing to the development of the practically viable Li-S batteries.

O-bridged Fe-W dual-atom co-anchored on carbon nitride for highly efficient solar-induced peroxymonosulfate activation

Constructing dual-atom catalysts (DACs) is an appealing strategy since the synergistic interaction of adjacent active metal atoms can improve the catalytic activity while maintaining high stability. However, the rational design of DACs and the insightful understanding of the structure-performance relationship remain the central tasks. Herein, we construct a unique DAC consisting of O-bridged Fe-W heterodimer embedded in graphitic carbon nitride (Fe-W-CN), which is synthesized by pre-fixing and pyrolysis process. In Fe-W-CN, the O-coordinated Fe-W atoms are anchored in CN vacancies through nitrogen atoms with N-Fe-O-W-N configuration. The W-O site acts as a “nail” to stable the Fe atom during oxygen-containing calcination, and the final formed N-Fe-O-W-N moiety also can resist the attack of strong oxidizing radicals to achieve high stability. The density functional theory calculation indicates that the Fe atom is the main active site for peroxymonosulfate (PMS) adsorption and activation. Meanwhile, electrons generated by photoexcited CN can accelerate the recycling of Fe3+/Fe2+ for high catalytic activity. Fe-W-CN exhibits a high CBZ removal efficiency through the activation of PMS, which is 6.9 times higher than CN. This work paves the way to develop novel DACs with stable and high catalytic efficiency.

Hydrogen Atom Adsorption-Induced Spin Reversal and Vacancies Boosting Hydrogen Evolution Reaction in Defective H-VS2 Monolayers

Spin reversal induced by adsorbates will cause intersite communication between the active and adjacent sites, which modulates the exchange coupling strength and spin alignment direction of adjacent atoms. Here, spin reversal induced by H adsorption and hydrogen evolution reaction (HER) performance of defective H-VS2 are studied by density-functional theory. The spin of V/S atoms around double S vacancies on different atomic layers (V2S) exhibits continuous reversals with H adsorption, which reverses once for S atoms around single V vacancy (VV). Moreover, the adsorption energies of the second H atom decreased in V2S- and VV-modified H-VS2 systems. Additionally, V2S and VV can activate the inert basal plane of H-VS2, and the increased antibonding filling and p-band center in H-VS2 with VV will weaken the interaction between S–H atoms and promote the desorption of H2, which causes lower Gibbs free energy in H-VS2 with VV than V2S and the pure H-VS2 monolayer.

Computational investigation of functionalized carbenes on dinitrogen activation

Activation of the dinitrogen triple bond is a crucial step in the overall fixation of atmospheric nitrogen into usable forms for industrial and biological applications. Current synthetic catalysts incorporate metal ions to facilitate the activation and cleavage of dinitrogen. The high price of metal-based catalysts and the challenge of catalyst recovery during industrial catalytic processes has led to increasing interest in metal-free catalysts. One step toward metal-free catalysis is the use of frustrated Lewis pairs (FLPs). In this study, we have examined 18 functionalized carbenes as FLPs to elucidate the influence of steric and electronic effects on the activation of dinitrogen. To test the effects of functionalization on dinitrogen activation, we have performed density functional theory (DFT), multireference, non and extended transition state-natural orbital for chemical valence (ETS-NOCV) calculations. Our results suggest that functional groups which introduce strong electron-withdrawing effects and/or engage in extended π/π* systems lead to the lowering of the dissociation energy of the dinitrogen bond, which further contributes to greater nitrogen activation. We conjecture that these effects are due to enhanced back-bonding capability of the p orbital of the carbene carbon atoms to the adjacent nitrogen atoms (increasing Lewis basicity of the carbene carbon atom) and enhanced stability of dissociated products. Our concluding remarks include opportunities to extend this activation study to explore the entire catalytic cycle with promising functionalized carbenes for experimental evaluation.

Strengthening and toughening mechanisms induced by metal ion cross-linking in wet-drawn bacterial cellulose films

Cellulose nanofibril (CNF) has become a renewable and sustainable building block for functional and structural materials. In this study, combining chemical structure analyses, mechanical experiments, and first principle calculations, we elaborate on the strengthening and toughening mechanisms for the wet-drawn bacterial cellulose (BC) films that contain metal ion crosslinks. Wet-drawing assists the alignment of CNFs, and multivalent metal ion cross-linking further improves the inter-fibril interactions. BC films cross-linked with Na+, Ca2+, Cu2+, Al3+, and Fe3+ all demonstrate improved mechanical strength than the as-received samples. Density functional theory (DFT) calculations reveal that besides the electrostatic forces between the metal ions and the adjacent carboxylate oxygen atoms, Cu2+ and Fe3+ can also form coordination bonds with the adjacent carboxylate oxygen atoms. Among all the five metal ions tried herein, Fe3+ introduces the strongest cross-links between nanofibrils through coordination bonds and electrostatic forces. The BC films cross-linked with Fe3+ exhibit high tensile strength and toughness of 451.51 MPa and 8.19 MJ∙m−3, respectively. The underlying mechanisms discovered herein open new possibilities for utilizing natural fibers.

Synergistic adsorption effect on Co3O4(1 1 0) surface to promote the ethanol sensing properties: Experiment and theory

A deep understanding of the relationship between the properties and structure of transition metal oxide semiconductor gas sensors is essential for optimizing sensor design. Comparing and analyzing the sensing properties of nanomaterials with different morphologies and crystal facets by combining the experiment analysis and the density functional theory (DFT) calculations could identify and understand the corresponding mechanisms at the atomic or ionic level. Here, grown Co3O4 nanosheet (Co3O4-NS) with exposed (111) facets, and Co3O4 nanorods (Co3O4-NR) with exposed (110) facets on alumina ceramic tubes were prepared and studied in sensing ethanol. The adsorption characteristics of ethanol on the sensor surface were analyzed by DFT calculation. The results demonstrated that the sensing performance of Co3O4-NR was superior to Co3O4-NS. The adsorption of hydroxyl groups in ethanol was better than the methyl groups on the surface. The oxygen and hydrogen atoms from the hydroxyl groups in ethanol had the lowest adsorption energies (Eads = −3.44 eV) when they interact with the Co atom and the indirectly adjacent low-coordinate oxygen atoms on the (110) surface, respectively. The synergistic adsorption of target gases by exposed surface atoms induced superior sensing properties of the material.

Classification of properties and their relation to chemical bonding: Essential steps toward the inverse design of functional materials.

To design advanced functional materials, different concepts are currently pursued, including machine learning and high-throughput calculations. Here, a different approach is presented, which uses the innate structure of the multidimensional property space. Clustering algorithms confirm the intricate structure of property space and relate the different property classes to different chemical bonding mechanisms. For the inorganic compounds studied here, four different property classes are identified and related to ionic, metallic, covalent, and recently identified metavalent bonding. These different bonding mechanisms can be quantified by two quantum chemical bonding descriptors, the number of electrons transferred and the number of electrons shared between adjacent atoms. Hence, we can link these bonding descriptors to the corresponding property portfolio, turning bonding descriptors into property predictors. The close relationship between material properties and quantum chemical bonding descriptors can be used for an inverse material design, identifying particularly promising materials based on a set of target functionalities.