Single Atom Research Articles

Deciphering the Nitrogen Activation Mechanisms on Group VIII Single Atoms at MoS2.

The activation of nitrogen (N2) is vital for sustainable ammonia production and nitrogen fixation technologies. This study employs density functional theory (DFT) to investigate the nitrogen activation and reduction capabilities of Group VIII single-atom catalysts anchored on MoS2. Among these, osmium anchored on MoS2 (Os@MoS2) emerged as the most promising catalyst, exhibiting the highest N2 activation and the lowest nitrogen reduction reaction (NRR) overpotential (0.624 V). A pronounced "electron drift" effect was observed for Os@MoS2, leading to significant charge redistribution that weakens the N ≡ N triple bond, facilitating its activation. The N-N dissociation energy barrier at the *N-NH2 intermediate was calculated to be only 0.82 eV, confirming Os@MoS2's superior catalytic efficiency. Detailed analyses, including electrostatic potential maps, electron localization functions, spin density, and charge transfer, revealed the pivotal role of orbital interactions in driving N2 activation. Interestingly, the trends in adsorbed N2 bond energies and NRR overpotentials showed a consistent diagonal pattern across the Group VIII catalysts, emphasizing the importance of electronic and geometric factors. This work offers valuable insights into nitrogen activation mechanisms and provides a framework for designing efficient catalysts, highlighting Os@MoS2's potential in sustainable ammonia synthesis.

In-Situ Anchoring of Co Single-Atom Synergistically with Cd Vacancy of Cadmium Sulfide for Boosting Asymmetric Charge Distribution and Photocatalytic Hydrogen Evolution.

In the context of reshaping the energy pattern, designing and synthesizing high-performance noble metal-free photocatalysts with ultra-high atomic utilization for hydrogen evolution reaction (HER) still remains achallenge. In a streamlined synthesis process, in-situ single atom anchoring is performed in parallel with HER by irradiating a precursory defect-state CdS/Co suspension (Co-DCdS-Ss) system under simulated sunlight and the in-situ synthesizing single-atom Co photocatalyst (Co5:DCdS) exhibits further improved catalytic performance (60.10 mmolg-1h-1) compared with Co-DCdS-Ss (18.09 mmolg-1h-1), reaching an apparent quantum yield of 57.6% at 500nm and a solar-chemical energy conversion efficiency (SCC) of 6.26% at AM 1.5G. In-depth characterization tests and density functional theory (DFT) calculations prove that the anchoring of Co single atom deepens the asymmetric charge distribution of the two-coordination S atom adjacent to the cadmium vacancy (VCd). The synergy between electron delocalization VCd and Co single atom on the catalyst surface is constructed, which bifunctional sites responsible for boosting water adsorption-dissociation and hydrogen evolution. This study advances the understanding of the underlying mechanisms of synergy between surface defects and metal single atoms and opens a new horizon for the development of advanced materials in the field of photocatalysis.

Single-atom Ru modified flake g-C3N4 enhances photogenerated electron transport for rapid degradation of tetracycline antibiotics: Non-radical mechanism and ecotoxicity studies

Design of green and low-cost single-atom catalysts (SACs) with high-performance is key to moving photocatalytic degradation of antibiotics toward applications. In order to achieve SACs for large-scale manufacturing, we prepared ultrathin flake carbon nitride (FCN) by low-energy-consuming physical knockout means, and also applied an in situ growth strategy with stable and easy-operating effect to anchor the Ru element on FCN in the form of single atom. Notably, in the PMS/Vis/0.5Ru-FCN system, the degradation rate of tetracycline achieved 100 % in just five minutes, with an apparent rate constant of 0.236 min−1. Ru-FCN exhibits selective and stable determination due to narrow bandgap, unique photoresponsivity and low photogenerated carrier complexation rate. Mechanism investigation reveal that Ru-N4 sites accelerated the electron transfer between Ru-FCN and PMS, while the low oxidation state of Ru elements reduced the risk for metal corrosion. DFT calculations predict the attack sites of reactive oxygen species. This work provides a rational explanation for the charge transfer and resistance to external disturbance by Ru single atom, and it also provides a new direction to enhance the efficiency of water treatment.

Mesoporous carbon spheres modified with atomically dispersed iron sites for efficient electromagnetic wave absorption

Carbon materials have obtained some achievements in electromagnetic wave (EMW) absorption owing to their excellent electrical conductivity and low density. However, poor impedance matching and high electrical conductivity limit their EMW absorption properties. Metal single atoms absorbers have garnered considerable attention in EMW absorption, largely due to the high metal availability and special coordination structure, but the modulation of the EMW absorption properties still needs to be improved. Herein, atomically dispersed Fe sites embedded into the N-doped mesoporous carbon spheres (Fe–SAs/NC) were synthesized through a facile coordination-assisted polymerization assembly strategy without acid leaching treatment. Benefitting from abundant mesoporous structure, the Fe–SAs/NC displays large specific surface area (339 m2 g−1) and optimized impedance matching, which results in an effective reduction of the absorber density. The homogeneously dispersed Fe single atoms (Fe–SAs) on the carbon skeleton lead to the improvement in conduction and dipole polarization losses of Fe–SAs/NC, which endows Fe–SAs/NC with exceptional EMW absorption properties. Experimental results indicate that Fe–SAs/NC displays desirable EMW absorption properties with the minimal reflection loss of −52.5 dB at 2.8 mm and the effective absorption bandwidth of 4.8 GHz. The study provides valuable insights for the development of carbon materials modified with atomically dispersed metal sites to achieve high-efficient EMW absorbers.

Influence of non-metals doping on the structural, electronic, optical, and photocatalytic properties of rutile TiO2 based on density functional theory computations

This study investigates the influence of non-metal doping (C, F, N, and S) on the structural, electronic, and optical properties of rutile TiO2 using Hubbard-corrected density functional theory (DFT) within the Quantum ESPRESSO code. Rutile TiO2 is a promising material for environmental remediation and renewable energy applications. However, it has a large bandgap of 3.03 eV, which confines its use to UV light. By substituting oxygen atoms with a single dopant atom, we aim to shift the absorption edge toward the visible spectrum. Our findings reveal that doping with C, N, and S results in a redshift of the bandgap, while F doping does not exhibit this effect. The imaginary part of the dielectric function indicates shifted absorption edges for C, N, and S-doped TiO2, making them suitable for photocatalytic applications. Additionally, an increased refractive index after doping suggests the presence of excess charge carriers that affect light propagation. This work provides valuable insights for experimentalists exploring non-metal doping influences on rutile TiO2 for photocatalysis.

Indium Single Atoms Supported on S-Scheme Cu3P/TiO2 as a Photocatalyst for Hydrogen Production

Indium Single Atoms Supported on S-Scheme Cu₃P/TiO₂ as a Photocatalyst for Hydrogen Production

Iron Oxide Clusters as Electron Donors Under Light Enhance Oxygen Reduction Kinetics at Atomically Dispersed Fe for Photocatalytic CH4 Partial Oxidation.

Photocatalytic CH4 oxidation to CH3OH emerges as a promising strategy to sustainably utilize natural gas and mitigate the greenhouse effect. However, there remains a significant challenge for the synthesis of methanol by using O2 at low temperature. Inspired by the catalytic structure in soluble methane monooxygenase (MMO) and the corresponding reaction mechanism, we prepared a biomimetic photocatalysts with the decoration of Fe2O3 nanocluster and satellite Fe single atom immobilized on carbon nitride. The catalyst demonstrates an excellent CH3OH productivity of 5.02 mmol·gcat-1·h-1 with methanol selectivity of 98.5%. Mechanism studies reveal that the synergy between Fe2O3 nanocluster and Fe single atom establishes a dual-Fe site as MMO for O2 activation and subsequent CH4 partial oxidation. Moreover, the light excitation of Fe2O3nanoclusters with a relative narrow bandgap could deliver the electrons and protons to atomic Fe that facilitating the oxygen reduction kinetics for the robust of methanol synthesis.

Coordination dependent photocatalytic peroxymonosulfate activation on biomass derived Fe single atom catalysts for atrazine degradation

Challenges associated with uncontrollable metal coordination structures in biomass-derived single-atom catalysts (SACs) and their intricate impacts on photocatalytic peroxymonosulfate (PMS) activation pose significant hurdles for the application of photo-Fenton technology towards wastewater treatment. Herein, we employed a co-pyrolysis strategy using Enteromorpha prolifera (E. prolifera) to synthesize Fe SACs with varying Fe–NX coordination, i.e., Fe–N5 and Fe–N6. Fe–N6-based SAC achieved over 80% atrazine (ATZ) degradation in 15 min, with a degradation rate of 0.13 min−1, representing 2.6-fold improvement over SAC with Fe–N5 structure. Experimental and simulation results revealed that Fe–N6 active sites acted as electron donors, enhancing the delocalization of π-electrons and improving photocatalytic PMS activation. This SAC also exhibited high selectivity for 1O2 degradation pathway and impressive ATZ degradation in seawater, with notable chlorine resistance, underscoring its potential in environmental pollutant remediation. This work unveils the catalyst structure-photocatalytic PMS activation performance relationship, offering avenue for developing more sustainable and efficient biomass-derived SACs for wastewater treatment.

Dual Fe/I Single-Atom Electrocatalyst for High-Performance Oxygen Reduction and Wide-Temperature Quasi-Solid-State Zn-Air Batteries.

Oxygen reduction reaction (ORR) electrocatalysts are essential for widespread application of quasi-solid-state Zn-air batteries (ZABs), but the well-known Fe-N-C single-atom catalysts (SACs) suffer from low activity and stability because of unfavorable strong adsorption of oxygenated intermediates. Herein, the study synthesizes dual Fe/I single atoms anchored on N-doped carbon nanorods (Fe/I-N-CR) via a metal-organic framework (MOF)-mediated two-step tandem-pyrolysis method. Atomic-level I doping modulates the electronic structure of Fe-Nx centers via the long-range electron delocalization effect. Benefitting from the synergistic effect of dual Fe/I single-atom sites and the structural merits of 1D nanorods, the Fe/I-N-CR catalyst shows excellent ORR activity and stability, superior to Pt/C and Fe or I SACs. When the Fe/I-N-CR is employed as cathode for quasi-solid-state ZABs, a high power density of 197.9mW cm-2 and an ultralong cycling lifespan of 280h at 20mA cm-2 are both achieved, greatly exceeding those of commercial Pt/C+IrO2 (119.1mW cm-2 and 47h). In addition, wide-temperature adaptability and superior stability from -40 to 60 °C are realized for the Fe/I-N-CR-based quasi-solid-state ZABs. This work provides a MOF-mediated two-step tandem-pyrolysis strategy to engineer high-performance dual SACs with metal/nonmetal centers for ORR and sustainable ZABs.

Cu−based bimetallic sites' p-d orbital hybridization promotes CO asymmetric coupling conversion to C2 products

Hampered by sluggish C−C coupling kinetics, the low selectivity and efficiency have limited industrial applications of CO2 reduction into valuable multi-carbon products. A direct coupling of CO molecules or their coupling after hydrogenation, followed by the final synthesis of C2 products, can help to overcome these limitations potentially. In this study, a detailed high-throughput screening of bimetallic site catalysts comprising copper (Cu) and 28 other metal (M) atoms was conducted. The metal atoms Cu and M were anchored on a carbon nanotube (CNT) with six nitrogen (N6) defects (CuMN6@CNT), which possesses effective dual active sites for C−C coupling. The calculated results demonstrate that the CuGaN6@CNT catalyst exhibited favorable selectivity, with low theoretical overpotentials of −0.23 and −0.34 eV for ethanol and ethylene, respectively, surpassing most reported catalysts. The synergistic effect of Ga and Cu sites, along with their p-d states hybridization, results in an enhancement of Cu's d state dispersion and energy barriers reduction for C−C coupling. Additionally, the strain effect of the substrate CNT exhibits a direct correlation with the catalytic performance of CuGaN6@CNT by adjusting the d-band center of the Cu site and p-band center of the Ga site. These findings provide a novel insights into the electrocatalytic reduction of CO into valuable C2 products using bimetallic single atom catalyst, offering significant guidance for future research endeavors in this field.

Superior Singlet Oxygen Electrosynthesis via Neighboring Dual Molecular Oxygen Coactivation for Selective Tetracycline Detoxification

AbstractOxygen (O2) electroreduction offers a green approach for singlet oxygen (1O2) synthesis in wastewater contaminants detoxification. However, traditional single O2 activation on single‐metal catalytic sites seriously suffers from the kinetically‐unfavorable desorption of adsorbed superoxide species (•O2−*/•OOH*). Here, we demonstrate a novel dual O2 coactivation pathway on shortened Fe1−OV−Ti sites for superior 1O2 electrosynthesis through a rapid disproportionate process between surface‐confined •O2−*/•OOH*. Theoretical calculations combined with in situ electrochemical spectroscopies demonstrated that the shortened distance between Fe single atom and adjacent unsaturated Ti atom facilitates the direct recombination of surface‐confined Fe−•OOH and Ti−•OO− to yield 1O2, bypassing the formidable •O2−*/•OOH* desorption process. Impressively, Fe1−OV−Ti could realize an excellent 1O2 electrosynthesis rate of 54.5 μmol L−1 min−1 with an outstanding 1O2 selectivity of 97.6 % under neutral condition, surpassing that of Fe1−O−Ti (27.1 μmol L−1 min−1, 91.7 %). Using tetracycline (TC) as a model pollutant, the resulting Fe1−OV−Ti electrode achieved nearly 100 % degradation in 120 min at −0.6 V, meanwhile preventing the generation of toxic intermediates. This study provides a new 1O2 electrosynthesis strategy by controlling the distance of adjacent catalytic sites for the coactivation of dual molecular oxygen.

Designing C9N10 Anchored Single Mo Atom as an Efficient Electrocatalyst for Nitrogen Fixation.

Electrochemical nitrogen reduction reaction (NRR) is a promising route for realizing green and sustainable ammonia synthesis under ambient conditions. However, one of the major challenges of currently available Single-atom catalysts (SACs) is poor catalytic activity and low catalytic selectivity, which is far away from the requirements of industrial applications. Herein, first-principle calculations within the density functional theory were performed to evaluate the feasibility of a single Mo atom anchored on a g-C9N10 monolayer (Mo@g-C9N10) as NRR electrocatalysts. The results demonstrated that the gas phase N2 molecule can be sufficiently activated on Mo@g-C9N10, and N2 reduction dominantly occurs on the active Mo atom via the preferred enzymatic mechanism, with a low limiting potential of -0.48 V. In addition, Mo@g-C9N10 possesses a good prohibition ability for the competitive hydrogen evolution reaction. More impressively, good electronic conductivity and high electron transport efficiency endow Mo SACs with excellent activity for electrocatalytic N2 reduction. This theoretical research not only accelerates the development of NRR electrocatalysts but also increases our insights into optimizing the catalytic performance of SACs.

Apparatus for producing single strontium atoms in an optical tweezer array

Abstract We outline an experimental setup for efficiently preparing a tweezer array of $^{88}$Sr atoms. Our setup uses permanent magnets to maintain a steady-state two-dimensional magneto-optical trap (MOT) which results in a loading rate of up to $10^{8}$ s$^{-1}$ at 5 mK for the three-dimensional blue MOT. This enables us to trap $2\times10^{6}$ $^{88}$Sr atoms at 2 $\mu$K in a narrow-line red MOT with the $^{1}$S$_{0}$ $\rightarrow$ $^{3}$P$_{1}$ intercombination transition at 689 nm. With the Sisyphus cooling and pairwise loss processes, single atoms are trapped and imaged in 813 nm optical tweezers, exhibiting a lifetime of 2.5 minutes. We further investigate the survival fraction of a single atom in the tweezers and characterize the optical tweezer array using a release and recapture technique. Our experimental setup serves as an excellent reference for those engaged in experiments involving optical tweezer arrays, cold atom systems, and similar research.

Regulating Atomically-Precise Pt Sites for Boosting Light-Driven Dry Reforming of Methane.

Light-driven dry reforming of methane is a promising and mild route to convert two greenhouse gas into valuable syngas. However, developing facile strategy to atomically-precise regulate the active sites and realize balanced and stable syngas production is still challenging. Herein, we developed a spatial confinement approach to precisely control over platinum species on TiO2 surfaces, from single atoms to nanoclusters. The configuration comprising single atoms and sub-nanoclusters engenders pronounced electronic metal-support interactions, with resultant interfacial states prompting surface charge rearrangement. The unique geometric and electronic properties of these atom-cluster assemblies facilitate effective activation of CH4 and CO2, accelerating intermediate coupling and minimizing side reactions. Our catalyst exhibits an outstanding syngas generation rate of 34.41 mol gPt -1 h-1 with superior durability, displaying high apparent quantum yield of 9.1 % at 365 nm and turnover frequency of 1289 h-1. This work provides insightful understanding for exploring more multi-molecule systems at an atomic scale.

Computational screening of single-atom transition metals on boron-rich boron nitride nanosheets for efficient hydrogen evolution catalysis in all pH range.

Low-cost and high-efficiency catalysts are of crucial importance for the electrocatalytic hydrogen evolution reaction (HER). Two-dimensional (2D) boron nitride (B-N) compounds formed by the combination of boron and nitrogen atoms of group III and V elements are promising candidates for electrocatalytic HER due to their significant electronic properties. Hence, an electrocatalyst is computer-aided designed with isolated single atoms of 3d, 4d, and 5d transition metals supported on 2D B-N (B2N, B5N3, and B7N5) monolayers to fabricate single-atom catalysts (SACs) with an excellent HER performance. Moreover, pH modulations are considered to improve the HER activity theoretically based on first-principles calculation. Our results indicate that B-N compounds surface doping with transition metal atoms can effectively enhance the HER catalytic performance over a wide range of pH. Among all SACs studied, Co-, Ti-, V-, Nb-, Ru-, Tc-, Zr-, and Os-embedded B2N, Sc-, Cr-, Mn-, Ti-, and Y-embedded B5N3, and Sc- and Mn-embedded B7N5 have excellent catalytic activity under acidic conditions, while Mo-, Ir-, Re-, Ta-, and W-embedded B2N and Ti- and Fe-embedded B7N5 show high catalytic activity under alkaline conditions. Interestingly, Hf@B2N and V@B5N3 systems exhibit promising catalytic activity under acidic, neutral, and alkaline conditions. Our work offers cost-effective candidates with a wide pH range HER performance for exploring ideal electrocatalysts.

Electrocatalytic nitrite conversion to ammonia over Mn single atoms anchored on MoO3-x

Electrocatalytic reduction of NO2 to NH3 (NO2RR) offers a promising route to attain harmful NO2– removal and valuable NH3 production. Herein, Mn single atoms anchored on oxygen vacancy-rich MoO3-x (Mn1/MoO3-x) are developed as a high-performance catalyst for the NO2RR. Atom characterizations unravel that the isolated Mn atoms exist as Mn1-O5 moieties on MoO3-x. Theoretical calculations and in situ electrochemical spectroscopic measurements unveil that Mn1/MoO3-x follows a Langmuir-Hinshelwood mechanism to drive the NO2RR process, in which Mn1-O5 site facilitates the adsorption and activation of NO2– to form the intermediates, while MoO3-x substrate dissociates H2O to yield *H. The generated *H is then transferred from MoO3-x substrate to Mn1-O5 site which promotes the intermediate protonation to produce NH3. Remarkably, Mn1/MoO3-x in flow cell reaches the high NH3 yield rate of 546.25 μmol h−1 cm−2 and NH3-Faraday efficiency of 92.6 %, outperforming most reported NO2RR catalysts.

Quantum superpositions of current states in Rydberg-atom networks

Quantum simulation of many-body quantum systems using Rydberg-atom platforms has become of extreme interest in the last years. The possibility to realize spin Hamiltonians and the accurate control at the single atom level paved the way for the study of quantum phases of matter and dynamics. Here, we propose a quantum optimal control protocol to engineer current states: quantum states characterized by Rydberg excitations propagating in a given spatially closed tweezer networks. Indeed, current states with different winding numbers can be generated on demand. Besides those ones with single winding number, superposition of quantum current states characterized by more winding numbers can be obtained. The single current states are eigenstates of the current operator that therefore can define an observable that remains persistent at any time. In particular, the features of the excitations dynamics reflects the nature of current states, a fact that in principle can be used to characterize the nature of the flow experimentally without the need of accessing high order correlators. Published by the American Physical Society 2024

High density cobalt single atom catalysts for H2O2 electrosynthesis: A critical design of carbon nitride skeleton

Direct hydrogen peroxide (H2O2) electrosynthesis via the two-electron oxygen reduction reaction (ORR) provides aburgeoning alternative to the industrial anthraquinone process.In this work, based on first-principles calculations and a targeted structural search, we predicted a new two-dimensional (2D) carbon nitride monolayer, PH-CN, accompanied by high mechanical stability and adequate intrinsic pyrrolic N-rich network, such remarkable merits ensure its greatpotential as substrates. Herein, we demonstrate how the coordination environment regulates the electronic structure of the Co central atom and thus steers the ORR selectivity and activity using a series of control samples based on the most prevalent CoN4 moiety. As expected, the acquired P-CoN4 and PH-CoN4 show excellent H2O2electrosynthesis performance with low thermodynamic overpotential of 0.02 and 0.07 V, as well as extremely high Co loadings of 26.28 and 27.42 wt%, respectively. This work sheds light on how the carbon nitride skeleton affects catalytic activities on Co-N-C catalysts.

Pt Single Atom-Doped Triphasic VP-Ni3P-MoP Heterostructure: Unveiling a Breakthrough Electrocatalyst for Efficient Water Splitting.

Enhancement of an alkaline water splitting reaction in Pt-based single-atom catalysts (SACs) relies on effective metal-support interactions. A Pt single atom (PtSA)-immobilized three-phased PtSA@VP-Ni3P-MoP heterostructure on nickel foam is presented, demonstrating high catalytic performance. The existence of PtSA on triphasic metal phosphides gives an outstanding performance toward overall water splitting. The PtSA@VP-Ni3P-MoP performs a low overpotential of 28 and 261 mV for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) at a current density of 10 and 25 mA cm-2, respectively. The PtSA@VP-Ni3P-MoP (+,-) alkaline electrolyzer achieves a minimum cell voltage of 1.48 V at a current density of 10 mA cm-2 for overall water splitting. Additionally, the electrocatalyst exhibits a substantial Faradaic yield of ≈98.12% for H2 and 98.47% for O2 at a current density of 50 mA cm-2. Consequently, this study establishes a connection for understanding the active role of single metal atoms in substrate configuration for catalytic performance. It also facilitates the successful synthesis of SACs, with a substantial loading on transition metal phosphides and maximal atomic utilization, providing more active sites and, thereby enhancing electrocatalytic activity.

Regulating Atomically‐Precise Pt Sites for Boosting Light‐Driven Dry Reforming of Methane

AbstractLight‐driven dry reforming of methane is a promising and mild route to convert two greenhouse gas into valuable syngas. However, developing facile strategy to atomically‐precise regulate the active sites and realize balanced and stable syngas production is still challenging. Herein, we developed a spatial confinement approach to precisely control over platinum species on TiO2 surfaces, from single atoms to nanoclusters. The configuration comprising single atoms and sub‐nanoclusters engenders pronounced electronic metal‐support interactions, with resultant interfacial states prompting surface charge rearrangement. The unique geometric and electronic properties of these atom‐cluster assemblies facilitate effective activation of CH4 and CO2, accelerating intermediate coupling and minimizing side reactions. Our catalyst exhibits an outstanding syngas generation rate of 34.41 mol gPt−1 h−1 with superior durability, displaying high apparent quantum yield of 9.1 % at 365 nm and turnover frequency of 1289 h−1. This work provides insightful understanding for exploring more multi‐molecule systems at an atomic scale.