Single Atom Research Articles

Chemical vapor deposition assisted the construction of Fe clusters modified single-atom Fe sites for efficient ORR catalysis

Iron-based atomic single-site catalysts are a type of promising catalyst for oxygen reduction reactions. However, these catalysts are still faced with challenges such as insufficient catalytic activity and poor stability. Fe clusters and Fe single atoms were simultaneously loaded on porous carbon using chemical vapor deposition in this study. The aim is to induce the redistribution of electronic clouds on Fe single-atom sites through Fe clusters, improving their adsorption capacity for oxygen reduction reaction intermediates, and thus obtaining highly active catalysts for oxygen reduction reaction. Under alkaline conditions, the ORR activity of FeSA/FeAC@NC (half-wave potential E1/2 of 0.90 VRHE) was significantly higher than that of commercial Pt/C (0.87 VRHE) and FeSA@NC (0.87 VRHE). Furthermore, FeSA/FeAC@NC exhibited exceptional durability, with 97.5% current retention in the i-t stability test for 10,000s. Additionally, the zinc-air battery assembled with FeSA/FeAC@NC showed a power density of 225 mW cm−2 and an energy density of 1082.2 Wh kgZn−1, demonstrating considerable potential for practical applications.

Synergistic effects of Fe single atoms and Fe nanoparticles modulating the electronic configuration for photocatalytic water treatment

Synergistic effects of Fe single atoms and Fe nanoparticles modulating the electronic configuration for photocatalytic water treatment

Enhanced oxygen reduction reaction with rare-earth metal-based Ce-N-C catalyst

An atomically dispersed single atom catalyst based on rare-earth metal, Cerium embedded into the porous N-doped carbon (Ce-N-C), has been synthesized by using metal-organic framework method. The Ce-N-C catalyst have been physiochemically and electrochemically characterized in detail. Transmission electron microscope studies revealed atomically dispersed Ce atoms on the N-doped carbon support. The electrochemical oxygen reduction reaction (ORR) kinetics of Ce-N-C-3 catalyst revealed an admirable activity with a half-wave potential of 0.89 V, nearly equal to state-of-the-art Pt/C catalyst. The K-L plots and RRDE measurements revealed a nearly direct 4 electron reduction of O2 to H2O by Ce-N-C-3 catalyst. In addition, the chronoamperometry studies with a simulated H2O2 environments clearly revealed the significance of Ce3+/Ce4+ redox couple in deactivating hydrogen peroxide and/or hydroperoxide radicals. The commendable ORR activity, stability and peroxide resistance of Ce-N-C-3 catalysts is credited to the high surface area, atomically dispersed Ce atoms, formation of Ce-N4-C active sites in the catalysts, evidenced from the XPS analysis, in addition to the significance of Ce3+/Ce4+ redox couple in the catalyst. Most importantly, chronoamperometric studies revealed clear evidence of Ce3+/Ce4+ couple significance, helping in effectively mitigating the peroxide related detrimental effects to the ORR catalyst.

Direct Observations and Measurements of Single Atoms

Direct Observations and Measurements of Single Atoms

Support work-function dependent Fenton-like catalytic activity of Co single atoms for selective cobalt(IV)=O generation

In Fenton-like reactions, high-valent cobalt-oxo (CoIV=O) has attracted increasing interests due to high redox potential, long lifetime, and anti-interference properties, but its generation is hindered by the electron repulsion between the electron rich oxo- and cobalt centers. Here, we demonstrate CoIV=O generation from peroxymonosulfate (PMS) activation over cobalt single-atom catalysts (Co-SACs) using in-situ Co K-edge X-ray absorption spectra, and discern that CoIV=O generation is dependent on the support work-function (WF) due to the strong electronic metal-support interaction (EMSI). Supports with a high WF value like anatase-TiO2 facilitate the binding of PMS-terminal oxo-ligand to Co sites by extracting Co-d electrons, thus decreasing the generation barrier for the critical intermediate (Co-OOSO32−). The Co atoms anchored on anatase-TiO2 (Co-TiO2) exhibited enhanced CoIV=O generation and superior activity for sulfamethoxazole (SMX) degradation during PMS activation. The normalized steady-state concentration of CoIV=O in Co-TiO2/PMS system was three orders of magnitude higher than that of free radicals, and 1.3- to 11-fold higher than that generated in other Co-SACs/PMS systems. Co-TiO2/PMS sustained efficient removal of SMX with minimal Co2+ leaching under continuous flow operation, suggesting its attractive water purification potential. Overall, these results underscore the significance of support selection for enhanced generation of high-valent metal-oxo species and efficient PMS activation in supported metal SACs.

Hydrogen spillover enhances the selective hydrogenation of α,β-unsaturated aldehydes on the Cu–O–Ce interface

The industrially important selective hydrogenation of α,β-unsaturated aldehydes to allyl alcohol is still challenging to realize using heterogenous hydrogenation catalysts. Supported Cu catalysts have shown moderate selectivity, yet low activity for the reaction, due to the electronic structure of Cu. By anchoring atomically dispersed Pd atoms onto the exposed Cu surface of Cu@CeO2, we report in this work that hydrogen spillover activates the inert metal-oxide interfaces of Cu@CeO2 into highly effective and selective catalytic sites for hydrogenation under mild reaction conditions. The as-prepared catalysts exhibit much higher catalytic activity in the selective hydrogenation of acrolein than Cu@CeO2. Comprehensive studies reveal that atomically dispersed Pd species are critical for the activation and homolytic splitting of H2. The activated H atoms easily spill to the Cu–O–Ce interfaces as Cu–Hδ– and interfacial Ce–O–Hδ+ species, making them the active sites for hydrogenation of polar C=O bonds. Moreover, the weak adsorption of allyl alcohol on the Pd and Cu–O–Ce interfacial sites prevents deep hydrogenation, leading to selective hydrogenation of several α,β-unsaturated aldehydes. Overall, we demonstrate here a synergic effect between single atom alloy and the support for activation of an inert metal-oxide interface into selective catalytic sites.

Unveiling vacuum fluctuations and nonclassical states with cavity-enhanced tripartite interactions

Enhancing and tailoring light–matter interactions offer remarkable nonlinear resources with wide-ranging applications in various scientific disciplines. In this study, strong and deterministic tripartite “beamsplitter” (“squeeze”) interactions are constructed by utilizing cavity-enhanced nonlinear anti-Stokes (Stokes) scattering within spin–photon–phonon degrees of freedom. We explore exotic dynamical and steady-state properties associated with the confined motion of a single atom within a high-finesse optical cavity. Notably, we demonstrate the direct extraction of vacuum fluctuations of photons and phonons, which are inherent in Heisenberg’s uncertainty principle, without requiring any free parameters. Moreover, our approach enables the realization of high-quality single-quanta sources with large average photon (phonon) occupancies. The underlying physical mechanisms responsible for generating the nonclassical quantum emitters are attributed to the decay-enhanced single-quanta blockade and long-lived motional phonons, resulting in strong nonlinearity. This work unveils significant opportunities for hitherto studying unexplored physical phenomena and provides novel perspectives on fundamental physics dominated by strong tripartite interactions.

Additive single atom values for thermodynamics IV: Formula volume, enthalpy, absolute entropy and heat capacity for ionic solids - Hydrate and anhydrate data

Atom Sums are optimized additive values for the chemical elements which may be used to predict thermochemical values of inorganic solids. Since they are based on the elements of the Periodic Table they are a complete set of parameters, subject only to the availability of reference thermochemical data. In the present publication, optimized data is presented for ambient formula unit volumes, enthalpies, entropies and heat capacities for both inorganic hydrates and anhydrates. These data complement previously published Atom Sum parameters for formation reaction entropies and for formation reaction Gibbs energies as well as complementing earlier data for undifferentiated inorganic solids.

Single atom doping induced charge-specific distribution of Cu1-TiO2 for selective aniline oxidation via a new mechanism

Single atom doping induced charge-specific distribution of Cu1-TiO2 for selective aniline oxidation via a new mechanism

Laser driven generation of single atom Fe-N-C catalysts for the oxygen reduction reaction

Single-Atom Catalysts (SACs) have emerged as the ultimate solutions in challenging systems bridging the gap between homogeneous and heterogeneous catalysts. However, feasible synthesis methods are necessary to stabilize single metal atoms, increase catalyst loadings and scale up the synthesis. Due to its sluggish kinetics, the oxygen reduction reaction (ORR) is the main source of irreversibility in proton exchange membrane fuel cells (PEMFC). The most promising candidates to replace Pt-based catalysts for the ORR in fuel cells are the so-called Fe-N/C catalysts. These catalysts display high ORR activity in acidic and alkaline electrolytes. In this work, we propose a laser-driven pyrolysis approach to generate Fe-N/C SACs that involves decomposition of aerosolized iron-phthalocyanines. The resulting catalyst displays ORR activity in acidic and alkaline electrolytes, with competitive half-potential and kinetic current density values in comparison with state-of-the-art electrocatalysts.

Surface active sites and interphase engineering into metal oxide hydrates enabled by ions substitution for efficient water splitting

The expanding requirement of energy-effective and cost-efficient water electrolysis has prompted studies of earth-abundant metal-based electrocatalysts. In this study, we study the typical substitution strategies of cation (Pt) or anion (Se) for modifying surface active sites or interphase engineering to tune electronic structure of bimetallic nickel molybdenum oxide hydrates (NiMoO4·xH2O), thus effectively improving catalytic properties toward hydrogen evolution reaction (HER) or oxygen evolution reaction (OER). Result of the cation substitution achieves PtSA–NiMoO4·xH2O catalyst with abundant doped Pt single atoms on surface, which promotes high HER activity with a small overpotential of 73 mV at a current yield of 10 mA cm−2 in alkaline medium. Meanwhile, Se–NiMoO4·xH2O catalyst, an outcome of the anion substitution approach, has unique interfaces of NiSe-NiMoO4 heterostructure and thus exhibits a desired overpotential of only 297 mV for OER. The combination of PtSA–NiMoO4·xH2O(–)//Se–NiMoO4·xH2O(+) couple results in a two-electrode electrolyzer cell, which requires a small cell voltage of 1.48, 1.54 and 1.59 V to deliver a response of 10 mA·cm−2 at 75, 50 and 25 °C, respectively, along with negligible performance decay during 50 h operation. These results highlight the potential of our catalyst engineering strategies to achieve high-performance green hydrogen production.

Insights into the Single Atom and Support Interaction in Electrocatalytic Oxygen Evolution Reaction

Insights into the Single Atom and Support Interaction in Electrocatalytic Oxygen Evolution Reaction

Exploring fluorinated heptose phosphate analogues as inhibitors of HldA and HldE, key enzymes in the biosynthesis of lipopolysaccharide

The growing threat of bacterial resistance to antibiotics has led to the rise of anti-virulence strategies as a promising approach. These strategies aim to disarm bacterial pathogens and improve their clearance by the host immune system. Lipopolysaccharide, a key virulence factor in Gram-negative bacteria, has been identified as a potential target for anti-virulence agents. In this study, we focus on inhibiting HldA and HldE, bacterial enzymes from the heptose biosynthesis pathway, which plays a key role in lipopolysaccharide biosynthesis. We present the synthesis of two fluorinated non-hydrolysable heptose phosphate analogues. Additionally, the inhibitory activity of a family of eight heptose phosphate analogues against HldA and HldE was assessed. This evaluation revealed inhibitors with affinities in the low μM range, with the most potent compound showing inhibition constant values of 15.4 μM for HldA and 16.9 μM for HldE. The requirement for a phosphate group at the C-7 position was deemed essential for inhibitory activity, while the presence of a hydroxy anomeric group was found to be beneficial, a phenomenon rationalized through computational modeling. Additionally, the introduction of a single fluorine atom α to the phosphonate moiety conferred a slight advantage for inhibition. These findings suggest that mimicking the structure of d-glycero-β-d-manno-heptose 1,7-bisphosphate, the product of the phosphorylation step in heptose biosynthesis, could be a promising strategy to disrupt this biosynthetic pathway. In terms of the in vivo effects, these heptose phosphate analogues neither demonstrated significant LPS-disrupting effects nor exhibited growth inhibitory activity on their own. Additionally, they did not alter the susceptibility of bacteria to hydrophobic antibiotics. The highly charged nature of these molecules may hinder their ability to penetrate the bacterial cell wall. To overcome this limitation, alternative strategies such as incorporating protecting groups that facilitate their entry and can subsequently be cleaved within the bacterial cytoplasm could be explored.

Finding the best frequency dependent performance of 3d transition metals (Co, Ni, and Mn) substituted nano magnetite for miniaturizing device applications

Ferrite samples with enhanced magneto-dielectric properties are more essential in electromagnetic applications. Therefore, a parent composition of Fe3O4 has been modified by substituting 3d transition metal elements (Co, Ni, Mn) at a single Fe atom using the co-precipitation synthesis method. The structural properties of the synthesized Fe3O4, NiFe2O4, CoFe2O4, and MnFe2O4 samples have been evaluated from the X-ray diffraction patterns. The surface morphology and microstructures of the studied samples were studied by field emission scanning electron microscopy and the average grain size of all the studied samples varied from 60.11 to 106.03 nm. The magneto-dielectric properties were analyzed by frequency dependent permeability (μ) and permittivity (ε) measurements for the range of 100 Hz to 100 MHz. The conduction process for the synthesized ferrites has been noticed from the ac conductivity (σac). The localized relaxation mechanism for the studied ferrites has been observed from the variation of imaginary portion of the electric modulus (M") and the impedance (Z"). Moreover, the mismatch (Z/ηο) between the impedance of the antenna substrates (Z) made of the studied samples and air (ηο) has been evaluated from the permeability and permittivity. Finally, NiFe2O4 has been derived as a suitable ferrite for miniaturizing devices over a frequency range of 10 kHz-6.5 MHz.

ФИЗИКАЛЫК ПРОЦЕССТЕРДИ КОМПЬЮТЕРДИК МОДЕЛДӨӨ

The article studies the processes of using modern pedagogical technology of computer modeling of physical processes in teaching the subject of physics and presents its main results/ In the experiment, the skills of activating students' knowledge in the physics profile were implemented in computer science lessons with the help of modern pedagogical technologies. As research methods, it was proposed to use computer programs capable of accurately and clearly modeling physical processes and phenomena. The results obtained are the conditions for obtaining visual dynamic illustrations of physical phenomena in nature using computer programs of its simplified model. The scientific novelty of the results obtained allows us to explain to students and improve their fundamental knowledge through modeling physical processes. The practical significance of the results obtained is that with the help of computer simulation it is possible to explain physical phenomena and processes, i.e. ranging from the magnetic field in space to the structure of a single atom. Practical recommendations - development of didactic conditions for interdisciplinary communication of special disciplines in the formation of students' professional competence in the direction of physics and mathematics education.

Customized Heteronuclear Dual Single-Atom and Cluster Assemblies via D-Band Orchestration for Oxygen Reduction Reaction.

Advanced oxygen reduction reaction (ORR) catalysts, integrating with well-dispersed single atom (SA) and atomic cluster (AC) sites, showcase potential in bolstering catalytic activity. However, the precise structural modulation and in-depth investigation of their catalytic mechanisms pose ongoing challenges. Herein, a proactive cluster lockdown strategy is introduced, relying on the confinement of trinuclear clusters with metal atom exchange in the covalent organic polymers, enabling the targeted synthesis of a series of multicomponent ensembles featuring FeCo (Fe or Co) dual-single-atom (DSA) and atomic cluster (AC) configurations (FeCo-DSA/AC) via thermal pyrolysis. The designed FeCo-DSA/AC surpasses Fe- and Co-derived counterparts by 18 mV and 49 mV in ORR half-wave potential, whilst exhibiting exemplary performance in Zn-air batteries. Comprehensive analysis and theoretical simulation elucidate the enhanced activity stems from adeptly orchestrating dz 2-dxz and O 2p orbital hybridization proximate to the Fermi level, fine-tuning the antibonding states to expedite OH* desorption and OOH* formation, thereby augmenting catalytic activity. This work elucidates the synergistic potentiation of active sites in hybrid electrocatalysts, pioneering innovative targeted design strategies for single-atom-cluster electrocatalysts.

A ruthenium single atom nanozyme-based antibiotic for the treatment of otitis media caused by Staphylococcus aureus.

Staphylococcus aureus (S. aureus) infection is a primary cause of otitis media (OM), the most common disease for which children are prescribed antibiotics. However, the abuse of antibiotics has led to a global increase in antimicrobial resistance (AMR). Nanozymes, as promising alternatives to traditional antibiotics, are being extensively utilized to combat AMR. Here, we synthesize a series of single-atom nanozymes (metal-C3N4 SANzymes) by loading four metals (Ag, Fe, Cu, Ru) with antibacterial properties onto a crystalline g-C3N4. These metal-C3N4 display a rob-like morphology and well-dispersed metal atoms. Among them, Ru-C3N4 demonstrates the optimal peroxidase-like activity (285.3 U mg-1), comparable to that of horseradish peroxidase (267.7 U mg-1). In vitro antibacterial assays reveal that Ru-C3N4 significantly inhibits S. aureus growth compared with other metal-C3N4 even at a low concentration (0.06mg mL-1). Notably, Ru-C3N4 acts as a narrow-spectrum nanoantibiotic with relative specificity against Gram-positive bacteria. Biofilms formed by S. aureus are easily degraded by Ru-C3N4 due to its high peroxidase-like activity. In vivo, Ru-C3N4 effectively eliminates S. aureus and relieves ear inflammation in OM mouse models. However, untreated OM mice eventually develop hearing impairment. Due to its low metal load, Ru-C3N4 does not exhibit significant toxicity to blood, liver, or kidney. In conclusion, this study presents a novel SANzyme-based antibiotic that can effectively eliminate S. aureus and treat S. aureus-induced OM.

Co incorporated pentagraphene as an efficient single-atom catalyst for reduction of CO2: First-principles investigations

Hydrogenation of carbon dioxide (CO2) to formic acid is explored through density functional theory calculations over Co decorated penta-graphene (Co@PG) as single atom catalyst (SAC). Co is successfully stabilized over pentagraphene due to strong overlapping of Co-3d and C-2p states of pentagonal ring of pentagraphene near fermi level. The higher diffusion barrier for Co over pentagraphene evince that the clustering of Co atom is restricted. This suggests that Co@PG can be used as a catalyst for reducing CO2. Moreover, the Hirshfeld charge density, molecular electrostatic potential and spin density analysis indicates that the Co site is the highly active site for CO2 hydrogenation reaction. Both CO2 and H2 show strong interaction with Co@PG. In co-adsorbed state, the interactions are even larger due to greater mutual polarization of reactants and localization of positive charge on Co with adsorption energy of -2.57 eV. The hydrogenation can proceed at ambient temperature due to a small energy barrier of 0.29 eV, the competitive reaction i.e. CO hydrogenation with CO2 hydrogenations almost impossible over the catalyst surface due to larger energy barriers i.e. 1.98 eV. Thus, this work shows that Co@PG can be used as an efficient and promising catalyst for CO2 hydrogenation at room temperature.

OH‐Induced Surface Reconstitution in Single Atoms and Clusters Integrated Electrocatalysts for Self‐Adaptive Oxygen Electrocatalysis

AbstractThe integration of atom clusters and single atoms into a unified system represents a desirable approach for attaining enhanced catalytic performance. Nonetheless, the controllable synthesis of a single‐atom and nanocluster integrated system (SA‐NC) faces considerable challenges, and the mechanisms underlying the catalytic activity remain poorly understood. In this research, a cobalt‐based catalyst containing both coordinatively unsaturated single‐atom (CoN3) and small nanoclusters (Co@SA‐NC) is synthesized. The Co@SA‐NC not only facilitates charge and mass transfer due to the interconnected long‐range micromorphology, thus endowing efficient oxygen electrocatalytic reaction (ORR/OER), but also undergoes surface reconfiguration upon OH adsorption at high potentials in alkaline ORR/OER conditions. More appealingly, this OH‐involved reconfigured adaptive structure promotes optimization of energy barriers owing to the dynamic regulation from the bridged OH between Co single‐atom and cluster in the whole reaction process. Specific to the application metrics, a zinc–air battery assembled using the Co@SA‐NC catalyst exhibit targeted power density enhancement with 270 mW cm−2 in an alkaline medium. This work offers an effective insight into the study of SA‐NC catalytic reaction pathways for efficient ORR/OER catalysis.

Quantifying the contribution of lanthanum single atoms in photocatalytic Fenton-like processes with a rigorous benchmarking protocol

Quantifying the contribution of lanthanum single atoms in photocatalytic Fenton-like processes with a rigorous benchmarking protocol