Single Atom Research Articles

CO Oxidation at Low Temperatures over the Au Cluster Supported on Crystalline Silicotitanate.

Crystalline silicotitanate (CST) with a sitinakite structure has attracted considerable attention as an ion exchanger because of its anionic surface owing to SiO4 tetrahedral and TiO6 octahedral linked structures. In particular, the anionic surface of CST is advantageous in immobilizing single Au atoms derived from a cationic precursor such as Au(en)2Cl3 (en = ethylenediamine). In this study, a Au/CST catalyst was prepared and evaluated for CO oxidation. The transmission electron microscopy and X-ray photoelectron spectroscopy results suggest that Au single atoms and clusters (Auδ+, 0 < δ < 1) were supported on Na+-CST particles. The 1.0 wt % Au/CST catalyst yielded high catalytic activity for CO oxidation, where 50% CO oxidation was achieved at a low temperature of -13 °C. In the low-temperature region (from -84 to 20 °C), CO oxidation over Au/CST may progress through the well-known Langmuir-Hinshelwood mechanism. Conversely, the experimental results of CO oxidation without O2 confirmed that the reaction proceeded according to the Au-assisted Mars-van Krevelen mechanism using the lattice oxygens of the CST particles at temperatures above 20 °C. Therefore, this work contributes to the design of highly dispersed single-atom or cluster catalysts using the anionic surface of the microporous CST.

Biology-Based Synthesis of Nickel Single Atoms on the Surface of Geobacter sulfurreducens as an Efficient Electrocatalyst for Alkaline Water Electrolysis.

Single-atom metal catalysts are promising electrocatalysts for water electrolysis. Nickel-based electrocatalysts have shown attractive application prospects for water electrolysis. However, synthesizing stable Ni single atoms using chemical and physical approaches remains a practical challenge. Here, a facile and precise method for synthesizing stable nickel single atoms on the surface of Geobacter sulfurreducens using a microbial-mediated extracellular electron transfer (EET) process is demonstrated. It is shown that G. sulfurreducens can effectively anchor nickel single atoms on their surface. X-ray absorption near-edge structure and Fourier-transformed extended X-ray absorption fine structure spectroscopy confirm that the nickel single atom is coordinated to nitrogen in the cytochromes. The as-synthesized nickel single atoms on G. sulfurreducens exhibit excellent bifunctional catalytic properties for alkaline water electrolysis with low overpotential (η) to achieve current density (10mAcm-2) for both hydrogen evolution reactions (η = 80mV) and oxygen evolution reaction (η = 330mV) with minimal catalyst loading of 0.0015mgNicm-2. The nickel single-atom catalyst shows long-term stability at a constant electrode potential. This synthesis method based on the EET capability of electroactive bacteria provides a simple and scalable approach for producing low-cost and highly efficient nonnoble transition metal single-atom catalysts for practical applications.

N-Heterocyclic Carbene Coordinated Cu Single Atoms on Poly(ionic Liquid) for Selective Electroreduction of CO 2 to CH 4 at High Current Density

N-Heterocyclic Carbene Coordinated Cu Single Atoms on Poly(ionic Liquid) for Selective Electroreduction of CO ₂ to CH ₄ at High Current Density

Fully Exposed Ru Clusters for the Efficient Multi-Step Toluene Hydrogenation Reaction.

Liquid organic hydrogen carriers (LOHCs) are attractive platform molecules that play an important role in hydrogen energy storage and utilization. The multi-step hydrogenation of toluene (TOL) to methylcyclohexane (MCH) has been widely studied in the LOCHs systems, due to their relatively low toxicity and reasonable hydrogen storage capacity. Noble metal catalysts such as Ru has exhibited good performance in multi-step hydrogenation reactions, while the application is still hindered by their high cost and low specific activity. Therefore, the primary challenge lies in the development of noble metal catalysts with both robust activity and efficient atomic utilization. In this study, a series of Ru species ranging from single atoms, fully exposed clusters to nanoparticles were fabricated to investigate their structural evolution in the TOL multi-step hydrogenation reaction. The fully exposed and atomically dispersed Ru clusters, composed of an average of 3 Ru atoms, exhibit superior catalytic performance and recycle ability in TOL multi-step hydrogenation. Moreover, it delivers a high turnover frequency of 9850.3 h-1 under the relatively mild reaction (100 °C, 1.5 MPa), compared with those of single atoms and nanoparticles, and shows a notable advantage over catalysts reported in previous studies. From density functional theory (DFT) calculations, the overall barrier of the TOL multi-step hydrogenation reaction over the fully exposed Ru clusters is significantly lower than that of single atoms and nanoparticles, resulting in its higher activity. The present work provides an efficient strategy to regulate the reaction pathway of multi-step complicated catalytic reactions by designing fully exposed metal cluster catalysts.

Single-step conversion of methane-steam to methanol on single-atom Cu1/γ-Al2O3 catalyst prepared via electrostatic anchoring

Direct conversion of methane to methanol in heterogeneous catalysis is of paramount importance but remains a challenging issue in improving catalytic activity and selectivity. Here, we report that Cu single-atom sites anchored on γ-Al2O3 oxides (Cu1/γ-Al2O3) using surface electrostatic adsorption, are highly active (methanol yield of ∼47 mmol/molCu/h) and stable in continuous conversion of methane-steam to methanol at 200 °C, comparable to most of the state-of-the-art Cu-zeolite catalysts. The combined DFT calculation and isotope labeling experiments reveal the methane-to-methanol reaction pathway on Cu single-atom sites and methanol formation is the rate limiting step. The further theoretical study indicates that single Cu atom as active site can preferentially activate methane C-H bond instead of methanol and has larger advantage for highly-selective methanol yield compared with [Cu(II)-OH]+ and [CuOCu]2+ active sites. Our molecular-level findings on Cu1/γ-Al2O3 single-atom catalyst pave the way to prepare better non-zeolite catalysts for methane to methanol.

Unveiling the Composition-Dependent Catalytic Mechanism of Pt-Ni Alloys for Oxygen Reduction: A First-Principles Study.

Unveiling the composition-dependent catalytic mechanism of Pt-based alloy cathodes for the oxygen reduction reaction (ORR) helps improve the proton exchange membrane fuel cells. Using density functional theory calculations, this study investigates the ORR catalytic performance of the Pt-Ni system with various compositions (1.00, ∼0.99, 0.75, 0.50, 0.25, ∼0.01, and 0.00). The ordered solid solution PtNi3(111) system shows activity comparable to Pt(111) and is cost-effective. The Ni1/Pt(111) system, featuring a single Ni atom on the Pt(111) surface as a surface single-atom alloy (SSAA), demonstrates the highest activity with an overpotential of only 0.28, which could be further reduced to 0.21 V by decreasing the surface Ni concentration to 1/16 monolayer coverage. The predicted high activity of Ni1/Pt(111) is confirmed when considering factors such as the implicit solution environment, constant potential conditions, and protonation capability. Moreover, surface-adsorbed oxygen species driven by reaction conditions stabilize these single Ni atoms of Ni1/Pt(111) by preventing segregation and dissolution processes, thereby exhibiting a dual functionality. This study reveals the composition dependence of Pt-based alloys and highlights the stability mechanisms of SSAA catalysts during the ORR.

Ni Cluster-Decorated Single-Atom Catalysts Achieve Near-Unity CO2-to-CO Conversion with an Ultrawide Potential Window of ≈1.7V.

Developing efficient electrocatalysts for CO2 reduction to CO within a broad potential range is meaningful for cascade application integration. In this work, hydrogen spillover is created and utilized to cultivate a proton-rich environment via the simple thermolysis of a Ni-doped Zn coordination polymer (Zn CPs (Ni)) to create asymmetric Ni single atoms co-located with adjacent Ni nanoclusters on nitrogen-doped carbon, termed as NiNC&SA/N-C, which expedites the hydrogenation of adsorbed CO2. Therefore, the sample demonstrates near-unity CO2-to-CO conversion efficiency under pH-universal conditions in ultra-wide potential windows: -0.39 to -2.05V versus RHE with the current densities ranging from 0.1 to 1.0 A cm-2 in alkaline conditions, -0.83 to -2.40V versus RHE from 0.1 to 0.9 A cm-2 in neutral environments, and -0.98 to -2.25V versus RHE across 0.1 to 0.8 A cm-2 in acid conditions. Corresponding in situ measurements and density functional theory (DFT)calculations suggest that the enhanced H2O dissociation and more efficient hydrogen spillover on NiNC&SA/N-C (compared to NiSA/N-C) accelerate the protonation of adsorbed CO2 to form *COOH intermediates. This work emphasizes the significant role of proton spillover in CO2RR, opening novel avenues for designing high-performance catalysts applicable to various electrocatalytic processes.

Cerium single atom anchored silver selenide: A high-performance catalyst for hydrogen evolution reaction with ultra-low activation energy and enhanced stability

Single-atom catalysts (SAC) have enabled high electrocatalytic activity production because of the enormous active sites bearing catalysts for hydrogen evolution reaction (HER). Herein, we report cerium single atom (Cesa) anchored silver selenide (Ag2Se) via metal-chalcogenide interaction for high-performance HER evolution. The designed electrocatalyst possesses extraordinary electrochemical and optical properties, thus the Cesa-Ag2Se could be a potential catalyst for the photo-electrochemical HER process. The sluggish diffusion rate of the Ce atom within the Ag2Se facilitates the high stability and the dispersed Cesa displayed ∼2 eV of energy differences with the Ce dimer proving the formation of dispersed Cesa over Ag2Se is potentially favorable. The minimum energy pathway (MEP) suggested the Cesa-Ag2Se system established only 0.003 eV as an ultra-low activation energy barrier in order to produce H2, which is by far the finest performance of Ag2Se-based thermodynamically favourable catalysis. The accumulated electron density due to the presence of Cesa enabled the presence of a large number of potential active sites (Ce and Ag) for hydrogen adsorption, in addition, the supportive zero band gap of the Ag2Se accelerated the kinetics for HER. Ultimately, we employed the Wentzcovitch cell dynamics-based molecular dynamics study for H* adsorbed Cesa-Ag2Se that suggests the stability of the catalyst for 500 fs. The in-depth HER modelling using the Lennard-Jones force field demonstrated the insightful dynamics behaviour of the catalytical system.

Atomically dispersed Fe-N4 sites in activation of peroxymonosulfate for wastewater purification: Mechanism of non-radical pathways and their quantification

Single-atom catalysts are promising alternatives to homogeneous and heterogeneous catalysts in the advanced oxidation processes for contaminant degradation; however, quantifying the exact contribution of nonradical reactive oxygen species has remained challenging. Herein, Fe single atoms anchored on nitrogen-doped carbonaceous substrates (Fe SAs-N-C) were synthesized for peroxymonosulfate (PMS) activation toward pollutant degradation. Fe SAs-N-C achieved high activity within 30 min, which is 17.20 and 5.08 times higher than those of N-C catalysts without or with Fe nanoparticles, respectively. A synergistic mechanism of singlet oxygen (1O2) and electron transfer for dominating pollutant degradation was revealed. The former contributed 78.50 % while the latter contributed 21.50 % in pollutant elimination. Density functional theory calculations uncovered that the O atom in −SO4 moiety of PMS was adsorbed on the Fe atoms, leading to the OH bond elongation and generating 1O2. While the absorbed O atom in OO bond near to −SO4 moiety of PMS tended to enlarge the OO bond and accelerate the electron transfer. The adsorbed PMS was prone to being decomposed into 1O2 due to a lower energy barrier (0.43 eV) of 1O2 rate-determining step than that of electron transfer (0.95 eV). Fe-N4 sites are both electron transfer channels and 1O2 formation sites. This work provides insights into the quantitative contributions of non-radical active species to pollutant degradation.

Plasma‐electrified synthesis of atom‐efficient electrocatalysts for sustainable water catalysis and beyond

The downsizing of metal structures to the nano and atomic level, thereby creating nanoparticle catalysts (NPCs), sub‐nanometer cluster catalysts (SNCCs) or single atom catalysts (SACs), has gained significant interest. In particular, synthesizing these types of catalysts using low temperature plasma electrified methods is an emerging field which is highly applicable to electrochemical water splitting for the sustainable production of green hydrogen. Surface modification via plasma treatment provides a route for nanoparticle immobilization or single atom trapping which ensures high atom utilization during electrolysis reactions. Plasma can also be used to create NPCs, SNCCs and SACs from various precursors as well as modify their surface properties once formed which impacts significantly on the oxygen evolution reaction and hydrogen evolution reaction. Therefore, in this review we emphasize the role that low temperature plasma electrified synthetic strategies play in electrocatalyst development for water splitting reactions and explore the crucial relationship between the electronic and coordination environment of atom efficient catalysts and their resulting catalytic activity. We also discuss methods to characterize these types of catalysts and the possibility for scaling up this technology which will be required for commercial applications.

Photoinduction of Pt single atoms decorated on UiO-66-NH2 for photocatalytic extraction of uranium under open system

The photocatalytic method has been proven as one of the effective methods for uranium removal from radioactive wastewater. Herein, a photocatalyst UiO-66-NH2-Pt was prepared using the adsorption-photoinduction method. Pt was first adsorbed on the substrate and then photo-reduced under light irradiation to be doped into the structure of UiO-66-NH2. The characterization results implied the formation and atomic dispersion of Pt with a loading content of 1.90 wt%. The loading of Pt has promoted the effective separation and transfer of photogenerated electron-hole pairs, broadened the visible light adsorption range and narrowed down the bandgap, thus to enhance the photocatalytic activity. Then they were applied for the photo-removal of uranium under air atmosphere. The reaction rate of UiO-66-NH2-Pt was about 7 times that of pure UiO-66, confirming the higher photocatalytic activity after the loading of Pt. It showed good reusability and was also universal for different water matrix. The detection of hydroxyl radicals with EPR method indicated the formation of H2O2, which could react with uranyl ions to form metastudtite under air. This work further verified the feasibility of photoinduced synthesis of Pt single atom and provided a novel material for photocatalytic removal of uranyl ion under air.

Iron single atoms and nitrogen vacancies on graphitic carbon nitride synergically shallowing deep electron traps towards efficient photocatalytic ozonation

The coupling of photocatalysis and ozonation has been approved a very efficient strategy for hydroxyl radicals (•OH) production and wastewater decontamination, yet it remains challenging to enrich surface-reaching charges around reaction centers to accelerate this process. This paper explored the strategy of single-atoms (SAs) modification and defects control, aiming to enhance the activity of graphite carbon nitride (CN) in the visible light photocatalytic ozonation. It was found that the presence of iron SAs on CN greatly altered the impact of nitrogen vacancies (NVs), which behaved as recombination centers of photogenerated charge carriers and deteriorated activity of CN, while positively promoting the separation and migration of photogenerated carriers in the case for Fe-CNV (consist of iron SAs and NVs) catalysts. Based on photoluminescence (PL) emission, time-resolved PL spectra, ultrafast transient absorption spectroscopy and first-principles calculations, we found that adjacent iron SAs revived electrons trapped at NVs by elevating their energy level and mediating their interfacial transfer, leading to the decreased loss during electron transfer. This finding demonstrates the feasible tailor of energy level alignment for defect states to shallow deep electron traps.

Heteroatoms‐Stabilized Single Palladium Atoms on Amorphous Zeolites: Breaking the Tradeoff between Catalytic Activity and Selectivity for Alkyne Semihydrogenation

AbstractAs a fundamental industrial catalytic process, the semihydrogenation of alkynes presents a challenge in striking a balance between activity and selectivity due to the issue of over‐hydrogenation. Herein, we develop an efficient catalytic system based on single‐atom Pd catalysts supported on boron‐containing amorphous zeolites (Pd/AZ−B), achieving the tradeoff breaking between the activity and selectivity for the selective hydrogenation of alkynes. Advanced characterizations and theoretical density functional theory calculations confirm that the incorporated B atoms in the Pd/AZ−B can not only alter the geometric and electronic properties of Pd atoms by controlling the electron migration from Pd but also mitigate the interaction between alkene and the catalyst supports. This boosts the exceptional catalytic efficacy in the semihydrogenation of phenylacetylene to styrene under mild conditions (298 K, 2 bar H2), achieving a recorded turnover frequency (TOF) value of 24198 h−1 and demonstrating 95 % selectivity to styrene at full conversion of phenylacetylene. By comparison, the heteroatom‐free amorphous zeolite‐anchored Pd nanoparticles and the commercial Lindlar catalyst have styrene selectivities of 73 % and 15 %, respectively, under identical reaction conditions. This work establishes a solid foundation for developing highly active and selective hydrogenation catalysts by controllably optimizing their electronic and steric properties.

Heteroatoms-Stabilized Single Palladium Atoms on Amorphous Zeolites: Breaking the Tradeoff between Catalytic Activity and Selectivity for Alkyne Semihydrogenation.

As a fundamental industrial catalytic process, the semihydrogenation of alkynes presents a challenge in striking a balance between activity and selectivity due to the issue of over-hydrogenation. Herein, we develop an efficient catalytic system based on single-atom Pd catalysts supported on boron-containing amorphous zeolites (Pd/AZ-B), achieving the tradeoff breaking between the activity and selectivity for the selective hydrogenation of alkynes. Advanced characterizations and theoretical density functional theory calculations confirm that the incorporated B atoms in the Pd/AZ-B can not only alter the geometric and electronic properties of Pd atoms by controlling the electron migration from Pd but also mitigate the interaction between alkene and the catalyst supports. This boosts the exceptional catalytic efficacy in the semihydrogenation of phenylacetylene to styrene under mild conditions (298 K, 2 bar H2), achieving a recorded turnover frequency (TOF) value of 24198 h-1 and demonstrating 95 % selectivity to styrene at full conversion of phenylacetylene. By comparison, the heteroatom-free amorphous zeolite-anchored Pd nanoparticles and the commercial Lindlar catalyst have styrene selectivities of 73 % and 15 %, respectively, under identical reaction conditions. This work establishes a solid foundation for developing highly active and selective hydrogenation catalysts by controllably optimizing their electronic and steric properties.

Harnessing 4f Electron Itinerancy for Integrated Dual-Band Redox Systems Boosts Lithium-Oxygen Batteries Electrocatalysis.

In-depth comprehension and manipulation of band occupation at metal centers are crucial for facilitating effective adsorption and electron transfer in lithium-oxygen battery (LOB) reactions. Rare earth elements play a unique role in band hybridization due to their deep orbitals and strong localization of 4felectrons. Herein, we anchor single Ce atoms onto CoO, constructing a highly active and stable catalyst with d-fa dual-band redox center. It is discovered that the itinerant behavior of 4felectrons introduces an enhanced spin-orbit coupling effect, which facilitates ideal σ/π bonding and flexible adsorption between the Ce/Co active sites and *O. Simultaneously, the injection of localized Ce 4felectrons strengthens the orbital bonding capacity of Co-O, effectively inhibits the dissolution of Co sites and improves the structural stability of the cathode material. Bracingly, the Ce1/CoO-based LOB exhibits an ultra-low charge-discharge polarization (0.46 V) and stable cyclic performance (1088 hours). This work breaks through the traditional limitations in catalyst activity and stability, providing new strategies and theoretical insights for developing high-performance LOBs powered by rare-earth elements.

DFT insight into the structural, vibrational, and electronic properties of thin [110] Ge nanowires as anodic material for Li batteries

Germanium nanowires could be used to improve as anodic materials since their charge rate is better than that of the current graphite electrodes. In this work, we present a Density Functional Theory study of the effect of interstitial Li atoms on the vibrational, electronic, and mechanical properties of ultrathin hydrogen-passivated Ge nanowires (HGeNWs) with diamond structure, grown along the [110] crystallographic direction, and with a diameter of ∼14.4 Å. The interstitial Li atoms were placed at the tetrahedral positions (Td) reported as the more favorable ones. The phonon band structure of the HGeNWs reveals the existence of high frequency vibrations due to the hydrogen atoms at the nanowire surface. The effect of one interstitial Li atom in the nanowire leads to the apparition of three flat phonon bands almost independent of the collective vibrational states of the nanowire, reflecting a weak interaction between the Li atom and the neighboring ones; and a shift of the high vibrational modes to lower frequencies that results in more dispersive states. The electronic band structure confirms a transition from semiconducting to metallic behavior by adding a single Li interstitial atom per unit cell. The formation energies indicate that the nanowires with interstitial Li atoms are stable, and the average binding energy per Li atom slightly increases as a function of the concentration of Li atoms. The insertion of Li atoms in the nanowire leads to a volumetric expansion, without fracture or broken bonds. Even more, the redistribution of the electronic charge due to the Li atoms give the Ge-Ge bonds more axial elasticity and the values of the modulus of Young are almost constant for all studied concentrations of Li atoms. These theoretical results indicate an improvement of mechanical and electronic properties of Ge nanowires through the addition of interstitial Li atoms that could be important for their use as anodes in rechargeable Li batteries.

High-throughput screening of efficient graphdiyne supported transition metal single atom toward water electrolysis and oxygen reduction

Efficient single-atom electrocatalysts show great potential for application in the field of renewable energy. In this work, dispersion-corrected density functional theory (DFT) calculations based on high-throughput screening were used to identify effective graphdiyne (GDY) supported single-atom electrocatalysts (SAECs) for water electrolysis and the oxygen reduction reaction (ORR). The solvation effect on the electrocatalytic performance of the catalysts was carefully discussed. A general design principle was established to evaluate the activities of TM@GDY SAECs for ORR and oxygen evolution reaction (OER). ΔGOH* could serve as the sole descriptor for the onset potential of OER and ORR. Additionally, a universal structural descriptor φ, which is strongly related to ΔGOH*, was identified. This descriptor only includes intrinsic features such as the number of electrons in d orbitals and elemental electronegativity. Consequently, a structure-activity volcano was plotted. Combined with the electronic properties calculations, the mechanism behind the relationship between ΔGOH* and descriptor φ was deeply analyzed. Among the investigated candidates, TM@GDY (TM = Ni, Pt, Pd, Cu, Co, Rh, and Ag) are potential bifunctional electrocatalysts for OER and ORR. Three non-noble metal-based SAECs (Ni@GDY, Co@GDY, and Cu@GDY) and two noble metal-based SAECs (Rh@GDY and Ag@GDY) are potential trifunctional electrocatalysts for OER, ORR, and the hydrogen evolution reaction.

Front Cover: Transforming Red Phosphorus Photocatalysis: Dual Roles of Pre‐Anchored Ru Single Atoms in Defect and Interface Engineering

Front Cover: Transforming Red Phosphorus Photocatalysis: Dual Roles of Pre‐Anchored Ru Single Atoms in Defect and Interface Engineering

Front Cover: Transforming Red Phosphorus Photocatalysis: Dual Roles of Pre‐Anchored Ru Single Atoms in Defect and Interface Engineering

Front Cover: Transforming Red Phosphorus Photocatalysis: Dual Roles of Pre‐Anchored Ru Single Atoms in Defect and Interface Engineering

Enhanced catalytic activity of noble metal@borophene/WS2 heterojunction for hydrogen evolution reaction

Borophene is a promising two dimensional (2D) functional material due to the high surface area and good catalytic properties. However, the instability of borophene limits the large-scale application. In addition, the borophene as the van der Waals material is usually considered to have inert surfaces, which is difficult to capture hydrogen protons stably due to the absence of dangling bonds. To solve this problem, we construct a heterojunction structure using two up and coming 2D materials (borophene and WS2) and explore the interlayer catalytic activity of the borophene χ3/WS2 heterojunction by using the ab initio calculations. Four possible hydrogen adsorption sites are designed. The calculated result shows that this borophene χ3/WS2 heterojunction is found to exhibit excellent catalytic hydrogen evolution with the hydrogen adsorption ΔGH about −0.022 eV for H4 site and −0.053 eV for H1 site, respectively. Furthermore, we have doped the upper and low layers with the single atom of noble metals (Pt and Pd) to further enhance the catalytic activity of this χ3/WS2 heterojunction. When noble metal is doped in WS2 layer, it is found that the noble metal@borophene/WS2 exhibits good catalytic activity while the calculated ΔGH decreased to 0.005 eV in Pt@borophene/WS2 heterojunction. According to the Sabatier principle, this value is very close to zero, which means excellent catalytic properties in hydrogen evolution reaction (HER). Compared to pure Pt, the nature of low cost and high efficiency make Pt@borophene/WS2 heterojunction to become the promising catalyst for hydrogen evolution reaction.