Single-atom Materials Research Articles

Tailoring a High Loading Atomic Zinc with Weak Binding to Sodium Toward High-Energy Sodium Metal Batteries.

Single-atom materials provide a platform to precisely regulate the electrochemical redox behavior of electrode materials with atomic level. Here, a multifield-regulated sintering route is reported to rapidly prepare single-atom zinc with a very high loading mass of 24.7 wt.% by significantly improved diffusion kinetics and stronger charge transfer between zinc and nitrogen atoms. X-ray absorption near edge structure (XANES) spectra for Zn K-edges during the charge and discharge process verify the stable single-atom zinc structure and the reversible slight reduction and oxidation of Zn sites, which is much different from the previous report of the alloying reaction process. This result suggests atomic Zn acts as an active sites through weak binding with sodium to regulate the Na ion fluxes. Finally, Cu foil coated with a ≈2µm layer of such material exhibits a high Coulombic efficiency of ≈99.99% up to 1700 cycles at 1mAhcm-2. An ultra-low overpotential of 3mV and an unprecedented life span of over 3200h in a symmetrical cell is achieved. Due to the very thin coating layer, anode-free sodium battery fabricated by Na3V2(PO4)3 cathode displays a prominent energy density of 320WhKg-1, demonstrating strong potential in practical application.

Nickel single atoms anchored on a bipyridine-based covalent organic framework: boosting active sites for photodegradation of acetaminophen.

It remains crucial but challenging to construct single-atom photocatalysts based on covalent organic framework (COF) materials in a simple, fast, and controllable manner and to clarify their structure-efficacy relationship. Here, a single-atom photocatalyst (Ni-TpBpy) featuring atomically dispersed Ni sites with a high loading content and a specific tetra-coordinated N2-Ni-Cl2 environment in a bipyridine-based COF was for the first time rapidly synthesized using dielectric barrier discharge (DBD) plasma and a wet chemical method. Visible light-driven Ni-TpBpy can achieve 97.8% photodegradation efficiency of acetaminophen at 0.177 min-1 in 30 min, outperforming other advanced photocatalysts. Experimental studies and density-functional theory (DFT) calculation clarified the role of well-dispersed Ni active sites in enhanced photodegradation, which not only narrowed the bandgap, facilitating carrier separation and migration, but also promoted the generation of reactive superoxide radicals. This study represents the first use of single-atom Ni-TpBpy in the efficient photocatalytic degradation of emerging pollutants with remarkable stability and universality, bringing new insights into the application of COF-based single-atom materials in environmental remediation.

Roughing Nitrogen-Doped Carbon Nanosheets for Loading of Monatomic Fe and Electroreduction of CO2 to CO.

The catalyst is the pivotal component in CO2 electroreduction systems for converting CO2 into valuable products. Carbon-based single-atom materials (CSAMs) have emerged as promising catalyst candidates due to their low cost and high atomic utilization efficiency. The rational design of the morphology and microstructure of such materials is desirable but poses a challenge. Here, we employed different Mg(OH)2 templates to guide the fabrication of two kinds of amorphous nitrogen-doped carbon nanosheet-supported Fe single atoms (FeSNC) with rough and flat surface structures. In comparison to flat FeSNC with saturated FeN4 sites, the rough FeSNC (R-FeSNC) exhibited unsaturated FeN4-x sites and contracted Fe-N bond length. The featured structure endowed R-FeSNC with superior capacity of catalyzing CO2 reduction reaction, achieving an exceptional CO selectivity with Faradaic efficiency of 93% at a potential of -0.66 V vs. RHE. This study offers valuable insights into the design of CSAMs and provides a perspective for gaining a deeper understanding of their activity origins.

Single-Atom catalysts supported by nanographene networks for efficient CO2 electroreduction: A first-principles study

Single-atom materials based on novel 2D nanographene networks and 3d transition metal atoms are constructed. Their structural and thermal stabilities in addition to the catalytic performance toward CO2 reduction are investigated using DFT calculations. Single metal atoms namely, Sc, Ti... Zn are strongly held by the pore C-atoms with high binding energy. Moreover, the dynamical and thermal stabilities are proved by the real vibrational frequencies and the molecular dynamics simulations at 500 K. Comparing the free energy of hydrogen evolution with that of the determinant intermediate in CO2 reduction shows that all the 3d metals, except Cu and Mn, are selective to CO2 reduction. Although the 3d single atom catalysts require a high potential for the overall CO2 conversion to CH3OH or CH4, they show exceptional catalytic performance toward CO2 to CO conversion. The calculated overpotential for CO-production using Sc and Ti is extremely low at 0.13 V making them competitive with the expensive Pt-catalysts. The overall CO2 reduction can be enhanced by considering 4d metals; for instance, an Au-based catalyst significantly reduces the overall energy required for CO2 conversion to CH3OH. Therefore, the constructed single-atom materials with high stability and promising catalytic activity are potential candidates for CO2 electrolysis.

Highly Reversible Sodium Metal Batteries Enabled by Extraordinary Alloying Reaction of Single‐Atom Antimony

AbstractThe unique coordination configuration of single‐atom materials (SAMs) allows precise reaction control at atomic‐level and a potential of unusual electrochemical reaction. Nevertheless, it is a big challenge to prepare main group element with high loading content. Here, multifield‐regulated synthesis (MRS) technology is utilized to rapidly produce single‐atom antimony (Sb) metal with a high loading of 15 wt.%. Ab initio molecular dynamics simulations reveal the significantly enhanced reaction kinetics of Sb and nitrogen‐doped graphene by multi‐physics field coupling. Compared with common metallic Sb nanoparticles, atomically dispersed Sb displays remarkably improved electrochemical reaction kinetics and stable structure due to the negligible variation of stresses and volume expansion during the pseudocapacitive alloying‐dealloying process. Such extraordinary alloying reaction in well‐dispersed Sb atoms enabling homogeneous ion flow can serve as active nucleation sites for regulating even Na metal nucleation and growth. As a result, copper foil coated with only ≈3 µm thickness of such material exhibits a high Coulombic efficiency of up to 99.99%, an ultra‐low overpotential of 3 mV, and a long lifetime exceeding 2500 h in symmetrical cells. Furthermore, an anode‐free MRS‐SbSA||Na3V2(PO4)3 battery is constructed, which demonstrates exceptionally high energy density (≈362 Wh Kg−1), outstanding rate capability and good cycling stability.

Single-atom materials boosting wearable orthogonal uric acid detection

Uric acid (UA) is a vital biomarker for the diagnosis and management of various health conditions, including cardiovascular diseases, gout, kidney disorders, metabolic syndrome, and wound healing. Despite significant advances in wearable sensor technology, challenges persist in developing wearable sensors that are capable of maintaining high sensitivity, selectivity, and stability. In this study, we present an epidermal sensing platform enhanced with single-atom materials (SAMs) designed for flexible and orthogonal electrochemical detection of UA. We designed and synthesized an SAM with Fe-N5 active sites to boost the electrochemical sensing signals, integrating it with laser-engraved graphene (LEG) to fabricate a wearable SAM-based UA patch sensor. This design provides superior UA detection performance compared to sensors based on conventional nanomaterials. In addition, we enhanced the detection accuracy and range by using an orthogonal approach that combines direct oxidation through differential pulse voltammetry (DPV) along with parallel biocatalytic amperometric detection. The resulting SAM-based UA orthogonal sensor patch demonstrated exceptional performance in wearable applications through tests measuring sweat UA levels in subjects before and after consuming a purine-rich diet.Graphical

Engineering peripheral S-doped atomic Fe-N4 in defect-rich porous carbon nanoshells for durable oxygen reduction reaction and Zn-air batteries

Iron-nitrogen-carbon (Fe-N-C) single-atom materials have emerged as the most promising catalysts for the oxygen reduction reaction (ORR), which yet suffers from inadequate stability arising from the attack of ·OH and HO2· radicals generated by H2O2. In this study, density functional theory (DFT) calculations reveal that the presence of peripheral S atoms can regulate the electronic structure of the Fe center and suppress the formation of H2O2 to enhance the catalyst's durability. Thereafter, atomic Fe-N4 with peripheral S doping is intricately engineered in defect-rich porous carbon nanoshells (Fe-NS-C) through an adsorption-pyrolysis method. The incorporation of S not only optimizes the coordination microenvironment of Fe-N4 but also induces a larger specific surface area and richer defects. The Fe-NS-C catalyst displays remarkable ORR performance, featuring a half-wave potential (E1/2) of 0.90 V. Its low H2O2 yield (below 1.1 %) and excellent stability (10 mV day in E1/2 after 10,000 cycles) further underscore the superiority of Fe-NS-C. When employed as the cathode for Zn-air battery, Fe-NS-C achieves an impressive peak power density of 230.1 mW cm−2 and stable charge/discharge potentials over an extended duration of 150 h. This study presents an effective strategy for engineering efficient and durable single-atom electrocatalysts for ORR and Zn-air batteries.

Chloride ligand stablizes single-atom on nanoporous metal oxides in a pyrolysis process

Pyrolysis-induced single-atom (SA) immobilization is a facile approach for the large-scale synthesis of single-atom materials, which holds promising potential in catalysis. The transition behavior from metal precursor to SA is not yet fully understood. Here, we report that coordinating chloride ligands play a pivotal role in stabilizing Pt/Ir/Ru SA when pyrolyzing their precursors on nanoporous metal oxide (Co3O4, NiO, and Fe2O3). The electrochemical and spectroscopic analysis combined with theoretical calculations suggests a thermal-driven progressive decomposition of metal precursors. Pyrolysis at a critical temperature of 250 ℃ drives the formation of the Ir-O3 motif between the Ir-based precursor and the supporting Co3O4, whereas three residual chloride ligands remain coordinated on the top and prohibit them from reacting with free Ir-containing species. Ir-SA/Co3O4 with an Ir loading of up to 3 at.% is produced. For electrocatalytic oxygen evolution reaction, it delivers a current density of 10 mA/cm2 at an overpotential of only 220 mV, corresponding to 11-fold higher mass activity over their corresponding nanoclusers/Co3O4. Our work highlights the essential role of ligands in the formation of SA, offering new insights into the thermal stability of SA, as well as a new avenue to increasing the loading of SAs.

Molybdenum single-atoms decorated multi-channel carbon nanofibers for advanced lithium-selenium batteries.

The cathode in lithium-selenium (Li-Se) batteries has garnered extensive attention owing to its superior specific capacity and enhanced conductivity compared to sulfur. Nonetheless, the adoption and advancement of Li-Se batteries face significant challenges due to selenium's low reactivity, substantial volume fluctuations, and the shuttle effect associated with polyselenides. Single-atom catalysts (SACs) are under the spotlight for their outstanding catalytic efficiency and optimal atomic utilization. To address the challenges of selenium's low chemical activity and volume expansion in Li-Se batteries, through electrospun, we have developed a lotus root-inspired carbon nanofiber (CNF) material, featured internal multi-channels and anchored with molybdenum (Mo) single atoms (Mo@CNFs). Mo single atoms significantly enhance the conversion kinetics of selenium (Se), facilitating rapid formation of Li2Se. The internally structured multi-channel CNF serves as an effective host matrix for Se, mitigating its volume expansion during the electrochemical process. The resulting cathode, Se/Mo@CNF composite, exhibits a high discharge specific capacity, superior rate performance, and impressive cycle stability in Li-Se batteries. After 500 cycles at a current density of 1 C, it maintains a capacity retention rate of 82% and nearly 100% coulombic efficiency (CE). This research offers a new avenue for the application of single-atom materials in enhancing advanced Li-Se battery performance.

S-Doping Regulated Iron Spin States in Fe-N-C Single-Atom Material for Enhanced Peroxidase-Mimicking Activity at Neutral pH.

Designing biomimetic nanomaterials with peroxidase (POD)-like activity at neutral pH remains a significant challenge. An S-doping strategy is developed to afford an iron single-atom nanomaterial (Fe1@CN-S) with high POD-like activity under neutral conditions. To the best of knowledge, there is the first example on the achievement of excellent POD-like activity under neutral conditions by regulating the active site structure. S-doping not only promotes the dissociation of the N─H bond in 3,3″,5,5″-tetramethylbenzidine (TMB), but also facilitates the desorption of OH* by the transformation of iron species' spin states from middle-spin (MS FeII) to low-spin (LS FeII). Meanwhile, LS FeII sites typically have more unfilled d orbitals, thereby exhibiting stronger interactions with H2O2 than MS FeII, which can enhance POD-like activity. Finally, a one-pot visual detection of glucose at pH 7 is performed, demonstrating the best selectivity and sensitivity than previous reports.

A universal and scalable transformation of bulk metals into single-atom catalysts in ionic liquids

Single-atom catalysts (SACs) with maximized metal atom utilization and intriguing properties are of utmost importance for energy conversion and catalysis science. However, the lack of a straightforward and scalable synthesis strategy of SACs on diverse support materials remains the bottleneck for their large-scale industrial applications. Herein, we report a general approach to directly transform bulk metals into single atoms through the precise control of the electrodissolution-electrodeposition kinetics in ionic liquids and demonstrate the successful applicability of up to twenty different monometallic SACs and one multimetallic SAC with five distinct elements. As a case study, the atomically dispersed Pt was electrodeposited onto Ni3N/Ni-Co-graphene oxide heterostructures in varied scales (up to 5 cm × 5 cm) as bifunctional catalysts with the electronic metal-support interaction, which exhibits low overpotentials at 10 mA cm-2 for hydrogen evolution reaction (HER, 30 mV) and oxygen evolution reaction (OER, 263 mV) with a relatively low Pt loading (0.98 wt%). This work provides a simple and practical route for large-scale synthesis of various SACs with favorable catalytic properties on diversified supports using alternative ionic liquids and inspires the methodology on precise synthesis of multimetallic single-atom materials with tunable compositions.

Generating active metal/oxide reverse interfaces through coordinated migration of single atoms

Identification of active sites in catalytic materials is important and helps establish approaches to the precise design of catalysts for achieving high reactivity. Generally, active sites of conventional heterogeneous catalysts can be single atom, nanoparticle or a metal/oxide interface. Herein, we report that metal/oxide reverse interfaces can also be active sites which are created from the coordinated migration of metal and oxide atoms. As an example, a Pd1/CeO2 single-atom catalyst prepared via atom trapping, which is otherwise inactive at 30 °C, is able to completely oxidize formaldehyde after steam treatment. The enhanced reactivity is due to the formation of a Ce2O3-Pd nanoparticle domain interface, which is generated by the migration of both Ce and Pd atoms on the atom-trapped Pd1/CeO2 catalyst during steam treatment. We show that the generation of metal oxide-metal interfaces can be achieved in other heterogeneous catalysts due to the coordinated mobility of metal and oxide atoms, demonstrating the formation of a new active interface when using metal single-atom material as catalyst precursor.

Experimentally validated design principles of heteroatom-doped-graphene-supported calcium single-atom materials for non-dissociative chemisorption solid-state hydrogen storage

Non-dissociative chemisorption solid-state storage of hydrogen molecules in host materials is promising to achieve both high hydrogen capacity and uptake rate, but there is the lack of non-dissociative hydrogen storage theories that can guide the rational design of the materials. Herein, we establish generalized design principle to design such materials via the first-principles calculations, theoretical analysis and focused experimental verifications of a series of heteroatom-doped-graphene-supported Ca single-atom carbon nanomaterials as efficient non-dissociative solid-state hydrogen storage materials. An intrinsic descriptor has been proposed to correlate the inherent properties of dopants with the hydrogen storage capability of the carbon-based host materials. The generalized design principle and the intrinsic descriptor have the predictive ability to screen out the best dual-doped-graphene-supported Ca single-atom hydrogen storage materials. The dual-doped materials have much higher hydrogen storage capability than the sole-doped ones, and exceed the current best carbon-based hydrogen storage materials.

A single atom cobalt anchored MXene bifunctional platform for rapid, label-free and high-throughput biomarker analysis and tissue imaging

Few of single-atom materials have been served as platform to analyze small molecules for surface assisted laser desorption/ionization mass spectrometry (SALDI-MS). Herein, a novel single Co atom-anchored MXene (Co–N–Ti3C2) is prepared to achieve enhanced SALDI-MS and mass spectrometry imaging (MSI) performance for the first time. The Co–N–Ti3C2 films were prepared by a simple in situ self-assembly strategy to generate an efficient SALDI-MS platform. Compared to typical inorganic/organic matrices, Co–N–Ti3C2 films exhibit superior performance in small molecules detection with ultra-high sensitivity (LOD at amol level), excellent repeatability (CV <4%), clean background and wide analyte coverage, enabling accurate quantitative analysis of various low-concentration metabolites from 1 μL biofluid in seconds. Its usage efficiently enhanced SALDI-MS detection of various small-molecule biomarkers such as amino acids, succinic acid, itaconic acid, arachidonic acid, citrulline, prostaglandin E2, creatinine, uric acid, glutamine, D-mannose, cholesterol and inositol in positive ion mode. The blood glucose level in humans was successfully determined from a linearity concentration range (0.25–10 mM). Notably, the Co–N–Ti3C2 assisted SALDI-MSI enables study the spatial distribution of small molecules covering the range central to metabolomics at a high resolution on a tissue section. Furthermore, Co–N–Ti3C2 platform revealed a specific peak profile that distinguishes osteoarthritis (OA) from rheumatoid arthritis (RA) tissue. Density functional theory theoretical investigation revealed that single Co atoms anchored on Ti3C2 could highly enhanced the ionization ability of metabolites, resulting in high-sensitivity and heterogeneous metabolome coverage.

Data-driven rational design of single-atom materials for hydrogen evolution and sensing

Data-driven rational design of single-atom materials for hydrogen evolution and sensing

The Promising Seesaw Relationship Between Activity and Stability of Ru-Based Electrocatalysts for Acid Oxygen Evolution and Proton Exchange Membrane Water Electrolysis.

The development of electrocatalysts that are not reliant on iridium for efficient acid-oxygen evolution is a critical step towards the proton exchange membrane water electrolysis (PEMWE) and green hydrogen industry. Ruthenium-based electrocatalysts have garnered widespread attention due to their remarkable catalytic activity and lower commercial price. However, the challenge lies in balancing the seesaw relationship between activity and stability of these electrocatalysts during the acid-oxygen evolution reaction (OER). This review delves into the progress made in Ru-based electrocatalysts with regards to acid OER and PEMWE applications. It highlights the significance of customizing the acidic OER mechanism of Ru-based electrocatalysts through the coordination of adsorption evolution mechanism (AEM) and lattice oxygen oxidation mechanism (LOM) to attain the ideal activity and stability relationship. The promising tradeoffs between the activity and stability of different Ru-based electrocatalysts, including Ru metals and alloys, Ru single-atomic materials, Ru oxides, and derived complexes, and Ru-based heterojunctions, as well as their applicability to PEMWE systems, are discussed in detail. Furthermore, this paper offers insights on in situ control of Ru active sites, dynamic catalytic mechanism, and commercial application of PEMWE. Based on three-way relationship between cost, activity, and stability, the perspectives and development are provided.

Single-atom Zr embedded Ti4O7 anode coupling with hierarchical CuFe2O4 particle electrodes toward efficient electrooxidation of actual pharmaceutical wastewater

Electrocatalytic oxidation is commonly restricted by low degradation efficiency, slow mass transfer, and high energy consumption. Herein, a synergetic electrocatalysis system was developed for removal of various drugs, i.e., atenolol, florfenicol, and diclofenac sodium, as well as actual pharmaceutical wastewater, where the newly-designed single-atom Zr embedded Ti4O7 (Zr/Ti4O7) and hierarchical CuFe2O4 (CFO) microspheres were used as anode and microelectrodes, respectively. In the optimal reaction system, the degradation efficiencies of 40 mg L–1 atenolol, florfenicol, and diclofenac sodium could achieve up to 98.8%, 93.4%, and 85.5% in 120 min with 0.1 g L–1 CFO at current density of 25 mA cm–2. More importantly, in the flow-through reactor, the electrooxidation lasting for 150 min could reduce the COD of actual pharmaceutical wastewater from 432 to 88.6 mg L−1, with a lower energy consumption (25.67 kWh/m3). Meanwhile, the electrooxidation system maintained superior stability and environmental adaptability. DFT theory calculations revealed that the excellent performance of this electrooxidation system could be ascribed to the striking features of the reduced reaction energy barrier by single-atom Zr loading and abundant oxygen vacancies on the Zr/Ti4O7 surface. Moreover, the characterization and experimental results demonstrated that the CFO unique hierarchical structure and synergistic effect between electrodes were also the important factors that could improve the system performance. The findings shed light on the single-atom material design for boosting electrochemical oxidation performance.

Magnetic properties of 3d metal atoms embedded in a new two-dimensional carbon sheet

A first-principles study is performed to explore the magnetic properties of the 3d transition metal (TM) atoms embedded in a new two-dimensional(2D) nonmagnetic carbon sheet. By the adsorption of 3d metal atoms (M = Sc-Ni) on the single vacancy (SV) site of 2D carbon material, the M@SV complexes are nonmagnetic for M = Ti, Co and Ni. Other metal atoms doping can induce different magnetism. The magnetic moment of Sc@SV system mainly comes from the π electrons of carbon atoms, and these electrons virtual hopping leads to the ferromagnetic coupling interaction with Sc atom. For M = V, Cr, Mn and Fe systems, the more net spin electrons go the separate nonbonding d orbitals, giving the different magnetic moments. Meanwhile, due to the Hund’s rule, the metal atoms and the surrounding carbon atoms have the anti-ferromagnetic coupling interaction. By the simple spd hybridization model, we explore the origin of the various magnetism, and provide some new magnetic single-atom materials for the future spintronics devices and spin-dependent catalysts.

Single atom-based electrodes for alkali metal-ion batteries: Current progress and future perspectives

Alkali metal-ion batteries (Li/Na/K) are important energy storage systems due to their ample elemental reserves and suitable working voltage. Many electrode materials had been developed and utilized to seek higher capacity and cycle stability. Single atom materials (SAMs) have high active atom dispersion and are very promising. The active metal sites can promote the diffusion kinetics and adsorption of lithium, sodium and potassium ions, which plays a key role in improving the capacity and cycling-stability. However, the experimental investigation of SAMs in Li/Na/K is still in its infancy stage. In this mini review, the structural design and electrochemical performance of single atom electrode materials in Li/Na/K are systematically summarized. The current challenges and potential research directions of designing SAMs for high-performance electrodes are also discussed.

Hydroformylation over polyoxometalates supported single-atom Rh catalysts

Atomic dispersion of Rh on phosphotungstic acid (PTA) salts was achieved by a self-assembled precipitation method using alkali metal ions as coprecipitation reagents. During styrene hydroformylation, the supported Rh single-atom catalyst (Rh1/M-PTA, M refers to an alkali metal ion) demonstrated an optimum turnover frequency (TOF) of 1076 h^-1. With increasing ionic radius, the pore size of the catalysts increased in the following order: Rh₁/K-PTA<Rh₁/Rb-PTA<Rh₁/Cs-PTA. The catalytic activity showed the same trend, suggesting a positive correlation between pore size and hydroformylation performance. Further experimental data suggested that temperature is an important factor affecting not only the activity but also the selectivity. This study enriches the understanding of the structure and catalytic properties of PTA-supported single-atom materials. The cation-controlled synthesis of catalysts may also be applied to prepare other single-atom catalysts with tunable pore size distributions.