Metal Atom Catalysts Research Articles

Single and dual metal atom catalysts for enhanced singlet oxygen generation and oxygen reduction reaction

We demonstrate rational design of graphene-supported single and dual metal atom catalysts (SACs and DACs) for photocatalytic applications, such as singlet oxygen (1O2) sensitization and H2O2 production.

Correction: Single and dual metal atom catalysts for enhanced singlet oxygen generation and oxygen reduction reaction

Correction for ‘Single and dual metal atom catalysts for enhanced singlet oxygen generation and oxygen reduction reaction’ by Mohsen Tamtaji et al., J. Mater. Chem. A, 2023, https://doi.org/10.1039/D2TA08240C.

Boosting the dynamic reconstitution of FeCu–N4 sites via doping of bimetal nanoparticles during oxygen electrocatalysis

Dual metal atom catalysts with nitrogen coordination are emerging as promising materials that can be substituted for platinum group-based catalysts employed for the oxygen electroreduction reaction.

Electrochemical nitrogen fixation on single metal atom catalysts.

The electrochemical reduction of nitrogen (eNRR) offers a promising alternative to the Haber-Bosch (H-B) process for producing ammonia under moderate conditions. However, the inertness of dinitrogen and the competing hydrogen evolution reaction pose significant challenges for eNRR. Thus, developing more efficient electrocatalysts requires a deeper understanding of the underlying mechanistic reactions and electrocatalytic activity. Single atom catalysts, which offer tunable catalytic properties and increased selectivity, have emerged as a promising avenue for eNRR. Carbon and metal-based substrates have proven effective for dispersing highly active single atoms that can enhance eNRR activity. In this review, we explore the use of atomically dispersed single atoms on different substrates for eNRR from both conceptual and experimental perspectives. The review is divided into four sections: the first section describes eNRR mechanistic pathways, the second section focuses on single metal atom catalysts (SMACs) with metal atoms dispersed on carbon substrates for eNRR, the third section covers SMACs with metal atoms dispersed on non-carbon substrates for eNRR, and the final section summarizes the remaining challenges and future scope of eNRR for green ammonia production.

Theoretical investigations of electrochemical nitrogen reduction on single transition metal atom catalysts supported by 1T-MoSe2

The search for stable and efficient single-atom catalysts (SACs) for the electrocatalytic nitrogen reduction reaction (eNRR) has garnered significant theoretical interest. In this study, we evaluate the eNRR performance of eighteen two-dimensional 1T-MoSe2-supported transition metal single-atom catalysts (TM@1T-MoSe2, TM=V, Cr, Mn, Fe, Co, Ni, Nb, Mo, Tc, Ru, Rh, Pd, Ta, W, Re, Os, Ir, and Pt) using density functional theory calculations. We assess the stability of each TM@1T-MoSe2, as well as the limiting potential of eNRR and the ammonia selectivity on each stable TM@1T-MoSe2. Our results show that W@1T-MoSe2 is the most promising single-atom catalyst for eNRR, with a limiting potential of -0.23 V via the distal pathway starting from three co-adsorbed nitrogen molecules. Furthermore, the multi-adsorption of N2 on W@1T-MoSe2 effectively suppress the hydrogen evolution reaction, thus enhancing the selectivity of the eNRR. This research provides a promising avenue for the development of a new class of 1T-MoSe2-based single-atom catalysts for electrocatalytic ammonia synthesis.

A theoretical investigation of NO oxidation using single metal atom catalysts with boron nitride

The principal pollutant, nonstop emitted, is nitric oxide (NO), organized with a small amount of nitrogen dioxide (NO2). A significant technology for their removal is their reaction with ammonia via choosy catalytic reduction with the momentous bottleneck for held catalysts being the high temperature vital for the catalytic activity (200–400 °C). Using first-principles theoretical approaches, the catalytic processes and bonding analyses of NO oxidation over transition metal (SAC) scattered on the boron nitride (BN) surface have been comprehensively examined. For isolated TM atom catalysts, BN is a good support. O2@TM-BN, NO@TM-BN, ON@TM-BN, 2NO@TM-BN, 2O2@TM-BN, and NO + O2@TM-BN configurations and the binding energies were calculated. In comparison to the other TM-SACs, V-/Cr-BN was originate to be the most gifted SAC for NO oxidation. It was discovered that at ambient temperatures, V-/Cr-BN SAC is precise volatile for NO oxidation, with squat stimulation barriers to the rate-determining stages for (V and Cr) Eley Rideal (0.25, 0.02, 0.12, and 0.19 eV), Langmuir Hinshelwood (0.73 and 0.55 eV), and Termolecular Eley-Rideal (0.41 and 0.30 eV) mechanisms. A comparative analysis of the results revealed that Cr-BN NO oxidation is additional auspicious than V-BN NO oxidation. These discoveries offer important insights into the development of exceedingly capable and selective dissimilar SACs for NO oxidation with TMs.

Single Metal Atoms on Oxide Surfaces: Assessing the Chemical Bond through 17O Electron Paramagnetic Resonance.

ConspectusEven in the gas phase single atoms possess catalytic properties, which can be crucially enhanced and modulated by the chemical interaction with a solid support. This effect, known as electronic metal-support interaction, encompasses charge transfer, orbital overlap, coordination structure, etc., in other words, all the crucial features of the chemical bond. These very features are the object of this Account, with specific reference to open-shell (paramagnetic) single metal atoms or ions on oxide supports. Such atomically dispersed species are part of the emerging class of heterogeneous catalysts known as single-atom catalysts (SACs). In these materials, atomic dispersion ensures maximum atom utilization and uniform active sites, whereby the nature of the chemical interaction between the metal and the oxide surface modulates the catalytic activity of the metal active site by tuning the energy of the frontier orbitals. A comprehensive set of examples includes fourth period metal atoms and ions in zeolites on insulating (e.g., MgO) or reducible (e.g., TiO2) oxides and are among the most relevant catalysts for a wealth of key processes of industrial and environmental relevance, from the abatement of NOx to the selective oxidation of hydrocarbons and the conversion of methane to methanol.There exist several spectroscopic techniques able to inform on the geometric and electronic structure of isolated single metal ion sites, but either they yield information averaged over the bulk or they lack description of the intimate features of chemical bonding, which include covalency, ionicity, electron and spin delocalization. All of these can be recovered at once by measuring the magnetic interactions between open-shell metals and the surrounding nuclei with Electron Paramagnetic Resonance (EPR) spectroscopy. In the case of oxides, this entails the synthesis of 17O isotopically enriched materials. We have established 17O EPR as a unique source of information about the local binding environment around oxygen of magnetic atoms or ions on different oxidic supports to rationalize structure-property relationships. Here, we will describe strategies for 17O surface enrichments and approaches to monitor the state of charge and spin delocalization of atoms or ions from K to Zn dispersed on oxide surfaces characterized by different chemical properties (i.e., basicity or reducibility). Emphasis is placed on chemical insight at the atomic-scale level achieved by 17O EPR, which is a crucial step in understanding the structure-property relationships of single metal atom catalysts and in enabling efficient design of future materials for a range of end uses.

Sulfur-Coordinated Transition Metal Atom in Graphene for Electrocatalytic Nitrogen Reduction with an Electronic Descriptor.

The adjacent chemical microenvironment of single metal atoms in heterogeneous catalysis is crucial to their chemical activity for various catalytic processes. Here, based on first-principles calculations, 25 single transition metal atom catalysts coordinated to sulfur species embedded in graphene (TM-S4-G-SACs) are reported for nitrogen reduction under ambient condition. It shows that nine TM-S4-G-SACs (TM = Mo, Sc, Cr, V, W, Ti, Nb, Mn, and Re) are promising nitrogen reduction catalysts with an optimal potential of -0.425 V. Meanwhile, 18 TM-S4-G-SACs have better catalytic activity than those with nitrogen coordination. Particularly, the catalytic activity of TM-S4-G-SACs and the adsorption energy of intermediate NH2* conform to a volcano-type correlation, which can be described by a universal electronic descriptor φ, defined by the electronegativity of the metal, adjacent coordinated atoms, and the valence electron occupancy. The above findings suggest the potential of sulfur-coordinated single metal atoms as electrocatalytic nitrogen reduction catalysts and an applicable descriptor to achieve optimal performance.

Single Metal Atom Catalysts and ORR: H-Bonding, Solvation, and the Elusive Hydroperoxyl Intermediate

The widely investigated oxygen reduction reaction (ORR) is well-known to proceed via two competing routes, involving two or four electrons, and yielding different reaction products, respectively. Both pathways are believed to share a common, elusive intermediate, namely, the hydroperoxyl radical. By exploiting a cobalt single-atom biomimetic model catalyst, based on a self-assembled monolayer of Co-porphyrins grown on an almost free-standing graphene sheet, we identify, in situ at room temperature in O2+H2O atmosphere, a hydroperoxyl-water cluster that is stabilized at the Co single-metal atom catalytic site. We show that the interplay between charge transfer, dipole and H-bonding, and water solvation behavior actually determines the hydroperoxyl-water complex stability, the Co-OOH bonding geometry, and, prospectively, opens to the engineered control of the selectivity of ORR pathways.

1+1>2: Learning from the interfacial modulation on single-atom electrocatalysts to design dual-atom electrocatalysts for dinitrogen reduction

Developing efficient electrocatalysts for converting dinitrogen to ammonia through electrocatalysis is of significance to the decentralized ammonia production. Here, through high-throughput density functional theory calculations, we demonstrated that the interfacial modulation of hexagonal boron nitride/graphene (hBN-graphene) could sufficiently improve the catalytic activity of the single transition metal atom catalysts for nitrogen reduction reaction (NRR). It was revealed that Re@hBN-graphene and Os@hBN-graphene possessed remarkable NRR catalytic activity with low limiting potentials of 0.29 V and 0.33 V, respectively. Furthermore, the mechanism of the enhanced catalytic activity was investigated based on various descriptors of the adsorption energies of intermediates, where the synergistic effect of hBN and graphene in the hybrid substrate was found to play a key role. Motivated by the synergistic effect of hybrid substrate in single-atom catalysts, a novel strategy was proposed to efficiently design dual-atom catalysts by integrating the merits of both metal components. The as-designed dual-atom catalyst Fe-Mo@hBN exhibited more excellent NRR catalytic performance with a limiting potential of 0.17 V, manifesting the solidity of the design strategy. Our findings open new avenues for the search of heterostructure substrates for single-atom catalysts and the efficient design of dual-atom catalysts for NRR.

Mechanism of Catalytic Transfer Hydrogenation for Furfural Using Single Ni Atom Catalysts Anchored to Nitrogen-Doped Graphene Sheets.

Catalytic transfer hydrogenation (CTH) of α,β-unsaturated aldehydes using single metal atom catalysts supported on nitrogen-incorporated graphene sheet (M-Nx-Gr) materials has attracted increasing attention recently, yet the reaction mechanism remains to be explored. Compared to the Ni-N4-Gr model in which the dissociation of isopropanol is highly unfavorable as a result of steric hindrance and inertness of the Ni-N4 site embedded in graphene, the Ni-N3 site in Ni-N3-Gr is more active and facilitates the formation of *H with isopropanol as the H donor, where the dissociation of H from isopropanol with an energy barrier of 0.83 eV is the rate-determining step. An alternative reaction path starts from the coadsorption of isopropanol and furfural molecules at the Ni-N3 site, followed by a direct hydrogen transfer between the two molecules; however, the rate-determining step has a much higher energy barrier of 1.32 eV. Our calculations suggest that the hydrogenation of the aldehyde group is kinetically more favorable than the C═C hydrogenation, revealing the high chemoselectivity of furfural to furfuryl alcohol. Our investigations reveal that the CTH mechanism using the Ni-N3-Gr catalyst is different from that on traditional metal oxides, where the former has only one single active site, while two active sites are required for the latter. The proposed reaction mechanism of CTH for furfural in this study should be helpful to guide the design of single metal atom catalysts with appropriate N coordination for application in chemoselective hydrogenation reactions.

Theoretical study of single transition metal atom catalysts supported on two-dimensional Nb2NO2 for efficient electrochemical CO2 reduction to CH4

The design of highly efficient catalysts for electrochemical reduction CO2 (ECR) to value-add chemicals and fuels is important for CO2 conversion technologies. In this work, earth abundant transition metal (TM = V, Cr, Mn, Fe, Co and Ni) atoms embedded into two-dimensional (2D) Nb2NO2 (TM@Nb2NO2) as single-atom catalysts (SACs) for ECR was investigated by first-principles study. We demonstrated that Nb2NO2 can be an excellent substrate for anchoring single TM atom due to its excellent stability and electronic conductivity. Besides, V, Cr and Ni@Nb2NO2 could effectively promote CO2 adsorption and reduction. All TM@Nb2NO2 exhibit high selectivity towards CH4, and V, Cr and Ni@Nb2NO2 show low limiting potentials. The activity origin was revealed by analysing adsorption energy, d band centre, bonding/antibonding population and the change of valence state of TM atoms.

Role of the Metal Atom in a Carbon-Based Single-Atom Electrocatalyst for LiS Redox Reactions.

Carbon-based single metal atom catalysts (SACs) are being extensively investigated to improve the kinetics of the Li-S redox reaction, which is greatly important for batteries with cell-level energy densities >500Whkg-1 .However, there are contradictory reports regarding the electrocatalytic activities of the different metal atoms and the role of the metal atom in LiS chemistry still remains unclear. This is due to the complex relationship between the catalytic behavior and the structure of carbon-based SACs. Here, the catalytic behavior and active-site geometry, oxidation state, and the electronic structure of different metal centers (Fe/Co/Ni) embedded in nitrogen-doped graphene, and having similar physicochemical characteristics, are studied. Combining X-ray absorption spectroscopy, density functional theory calculations, and electrochemical analysis, it is revealed that the coordination-geometry and oxidation state of the metal atoms are modified when interacting with sulfur species. This interaction is strongly dependent on the hybridization of metal 3d and S p-orbitals. A moderate hybridization with the Fermi level crossing the metal 3d band is more favorable for LiS redox reactions. This study thus provides a fundamental understanding of how metal atoms in SACs impact LiS redox behavior and offers new guidelines to develop highly active catalytic materials for high-performance LiS batteries.

Constructing Synergistic Zn‐N4 and Fe‐N4O Dual‐Sites from the COF@MOF Derived Hollow Carbon for Oxygen Reduction Reaction

Dual‐metal atom catalysts have been demonstrated to display higher catalytic activity and selectivity than that of solo metal atom catalysts toward oxygen reduction reaction (ORR). However, it is difficult to construct synergistic sites between different atoms even though they are immobilized in the same support, because their low‐density distribution resulted in the long distance between each other. Herein, a synergistic bimetal atomic electrocatalyst for ORR, which has highly dense Zn‐N4 (12.2 wt.% for Zn) and Fe‐N4O sites, from a core–shell hybrid of a covalent organic framework (COF) and a metal–organic framework (MOF) is demonstrated. The resultant catalyst displays a high activity for ORR with a half‐wave potential of 0.89 V vs reversible hydrogen electrode (RHE) in 0.1 m KOH, which is 50 mV more positive than that of Pt/C. The operando ANES confirms both Zn and Fe sites in the catalyst as active centers, and demonstrates that Fe sites have higher activity in the ORR process. Density functional theory (DFT) calculations further confirm the synergistic effect enables to improve the activity for both Fe sites and Zn sites in ORR. This work provides a new insight to develop ORR catalysts from COFs and MOFs.

Single metal atoms catalysts—Promising candidates for next generation energy storage and conversion devices

AbstractSingle‐metal‐atom catalysts (SMACs) with the merits of maximum atom utilization, peculiar electronic structure, and adjustable coordination environment, have emerged as the rising stars. They are not only regarded as the promising electrocatalysts, but also show unconventionally excellent alkali storage, thus enabling them for energy devices. In this work, we review the up‐to‐date progress of single metal atom catalysts including the detailed synthetic strategies and all sorts of applications in energy storage and conversion. In addition, we also discuss intrinsic catalytic effects, degradation mechanism, modulation approaches, support structure design, current challenges, and potential development trends. This work may shed light on developing high‐performance SMACs using a variety of strategies for catalytic and energy applications.image

Metal coordination in C2N-like materials towards dual atom catalysts for oxygen reduction.

Single-atom catalysts, in particular the Fe–N–C family of materials, have emerged as a promising alternative to platinum group metals in fuel cells as catalysts for the oxygen reduction reaction. Numerous theoretical studies have suggested that dual atom catalysts can appreciably accelerate catalytic reactions; nevertheless, the synthesis of these materials is highly challenging owing to metal atom clustering and aggregation into nanoparticles during high temperature synthesis treatment. In this work, dual metal atom catalysts are prepared by controlled post synthetic metal-coordination in a C2N-like material. The configuration of the active sites was confirmed by means of X-ray adsorption spectroscopy and scanning transmission electron microscopy. During oxygen reduction, the catalyst exhibited an activity of 2.4 ± 0.3 A gcarbon−1 at 0.8 V versus a reversible hydrogen electrode in acidic media, comparable to the most active in the literature. This work provides a novel approach for the targeted synthesis of catalysts containing dual metal sites in electrocatalysis.

Theoretical Study of Single Transition Metal Atom Catalysts Supported on Two-Dimensional Nb2no2 for Efficient Electrochemical Co2 Reduction to Ch4

Theoretical Study of Single Transition Metal Atom Catalysts Supported on Two-Dimensional Nb2no2 for Efficient Electrochemical Co2 Reduction to Ch4

Graphene supported single metal atom catalysts for the efficient hydrogen oxidation reaction in alkaline media

Single Pt and Ni atoms anchored on the divacancy graphene exhibit both high activity and superior antioxidant capacity for the hydrogen oxidation reaction in alkaline fuel cells.

Highly Selective and Stable Isolated Non-Noble Metal Atom Catalysts for Selective Hydrogenation of Acetylene

Highly Selective and Stable Isolated Non-Noble Metal Atom Catalysts for Selective Hydrogenation of Acetylene

Origin of hetero-nuclear Au-Co dual atoms for efficient acidic oxygen reduction

The atomically dispersed dual metal atom catalysts exhibit significant promise for the electrochemical energy conversion technologies. Herein, the hetero-nuclear precious-non-precious (Au-Co) dual atoms have been synthesized and subsequently applied for the acidic oxygen reduction reaction (ORR). The (Au-Co) dual atoms exhibit an outstanding activity with half-wave potential (E1/2) of 0.82 V in 0.1 M HClO4. Additionally, the proton exchange membrane fuel cell (PEMFC) analysis reveals a peak power density of 360 mW cm−2 under H2/air condition. Co-N2C2 with axial Au atom moieties act as the active sites of the (Au-Co) dual atoms towards ORR. Further, *OH adsorbed on the Co atom induces a coordinated change in the adjacent Au atom symmetry, which leads the anti-bond spin orbitals to a low energy level, thus, further improving ORR performance. The development of (Au-Co) dual atoms via the regulation of d-orbitals symmetry provides an encouraging way to design highly efficient (electro)catalysts.