Termolecular Eley-Rideal Mechanism Research Articles

A single Mn atom supported by a boron-vacancy in a BN monolayer: An encouraging catalyst for CO oxidation

Single-atom catalysts (SACs) are known for their exceptional activity, primarily attributed to the abundance of low-coordinated metal atoms, which enable efficient activation of robust chemical bonds, including CO bonds. In this work, we explore the prospective utilization of a specific SAC, isolated Mn atoms supported on Boron nitrogen (Mn/BN), for CO oxidation. By analyzing the adsorption/co-adsorption energies of CO, O2, O2+CO, and 2CO, we create a set of screening criteria and conduct a comparative analysis of the chemical processes involved in CO oxidation. The Langmuir-Hinshelwood (LH), Eley-Rideal (ER), termolecular Langmuir-Hinshelwood (TLH) and termolecular Eley-Rideal (TER) mechanisms are investigated. Results indicate the ER and LH mechanisms feature pronouncedly lower barrier of 0.33 and 0.41 eV, respectively, for the rate-limiting step, than those of the TLH (0.72 eV) and TER (3.00 eV) mechanisms, suggesting that the ER and LH mechanisms are favorable at normal temperature. This study offers valuable insights that can inform future developments in the design of low-temperature CO oxidation processes utilizing SACs.

Termolecular Eley–Rideal pathway for catalytic oxidation of nitric oxide on [Pt2]0,± dimers using O2

AbstractA comprehensive density functional theory (DFT) investigation of the catalytic oxidation of NO to NO2 on neutral and charged [Pt2]0,± dimers has been considered employing M06L/def2TZVP level of theory. Single as well as co‐adsorption energies of NO and O2 molecules suggest that the traditional Langmuir Hinshelwood (LH) mechanism and less explored termolecular Eley–Rideal (TER) and termolecular Langmuir Hinshelwood (TLH) mechanisms, are suitable for a full catalytic reaction pathway in which two NO molecules are converted to two NO2 molecules, initiated by an activated O2 molecule. Activation barrier reveals that the TER mechanism is found to be more reliable in converting two NO molecules into two NO2 molecules on [Pt2]¯ dimer. In addition to shedding light on the intrinsic characteristics of Pt2 dimers, the study will serve as a benchmark for investigating the oxidation process of NO to NO2 utilizing models of termolecular chemical processes.

Heterogeneous Co1/P1Mo12O40 single-atom catalyst for CO oxidation via termolecular Eley-Rideal (TER) mechanism

Catalytic mechanisms, micro-kinetic and thermodynamics studies of Phosphomolybdic acid (PMA) supported non-noble metal (NNM1 = Sc1, Ti1, V1, Cr1, Mn1, Fe1, Co1, Ni1, Cu1, and Zn1) single-atom catalysts (SACs) are explored for carbon monoxide (CO) oxidation by using DFT calculations. The results reveal that Co1/P1Mo12O40 have demonstrated excellent ability to adsorb (CO, O2) molecules, resulting in significant charge transfer from the catalyst surface to the adsorbate, which is essential to produce CO2 under normal reaction conditions. The various reaction pathways, including Eley Rideal (ER), Langmuir Hinshelwood (LH), Termolecular Eley Rideal (TER), and Mars Van Krevelen (MvK) are explored for CO oxidation on Co1/P1Mo12O40 to authenticate the most auspicious reaction mechanism. The energy barrier for the TER mechanism was 0.41 eV, lower as compared to the other reported materials which suggests that the Co1/P1Mo12O40 SACs would be the most appropriate future material for CO oxidation. To further validate the results, we performed the microkinetic investigation which predicts the CO oxidation rate of 4.58 × 106 s − 1. The key role of spin-magnetic moment for the promotion of CO oxidation by using Co1 single-atom catalyst was revealed from the deep electronic analysis. The current results would provide appreciated guidelines for experimentalists to develop less expensive and more effective non-noble metal SACs for CO oxidation.

Stable single iron atom within two-dimensional porphyrin sheet catalysis for CO oxidation: A computational investigation

CO produced by incomplete combustion of fuel poses a great threat to the environment and human health. Single atom catalysis can increase the active site of the catalyst, but it is unstable and easy to agglomerate at the higher temperatures. A stable single iron atom two-dimensional porphyrin sheet (Fe–TDPS) was designed, which was as CO oxidation catalyst to reduce costs and increase catalytic activity, and the reaction mechanism was investigated by density functional theory. Fe–TDPS has good stability at 1000 K with the ab initio molecular dynamics simulation. Absorption energies suggested that both CO and O2 preferred to anchor at the Fe–N4 site. The mechanisms of CO oxidation, which have reacted on the Fe–TDPS, were explored by Langmuir–Hinshelwood, Eley–Rideal, and ter-molecular Eley–Rideal mechanisms. Ter-molecular Eley–Rideal mechanism was feasible because of the small energy barrier. Results indicated that Fe–TDPS can be used as a catalyst for CO oxidation in the mild condition.

CO oxidation on MXene (Mo2CS2) supported single-atom catalyst: A termolecular Eley-Rideal mechanism

Finding transition metal catalysts for effective catalytic conversion of CO to CO2 has attracted much attention. MXene as a new 2D layered material of early transition metal carbides, nitrides, and carbo-nitrides is a robust support for achoring metal atoms. In this study, the electronic structure, geometries, thermodynamic stability, and catalytic activity of MXene (Mo2CS2) supported single noble metal atoms (NM = Ru, Rh, Pd, Ir, Pt and Au) have been systematically examined using first-principles calculations and ab initio molecular dynamic (AIMD) simulations. First, AIMD simulations and phonon spectra demonstrate the dynamic and thermal stabilities of Mo2CS2 monolayer. Three likely reaction pathways, Langmuir-Hinshelwood (LH), Eley-Rideal (ER), and Termolecular Eley–Rideal (TER) for CO oxidation on the Ru1- and Ir1@Mo2CS2 SACs, have been studied in detail. It is found that CO oxidation mainly proceeds via the TER mechanism under mild reaction conditions. The corresponding rate-determining steps are the dissociation of the intermediate (OCO-Ru1-OCO) and formation of OCO-Ir1-OCO intermediate. The downshift d-band center of Ru1- and Ir1@Mo2CS2 help to enhance activity and improve catalytst stability. Moreover, a microkinetic study predicts a maximum CO oxidation rate of 4.01 × 102 s-1 and 4.15 × 103 s-1 (298.15 K) following the TER pathway for the Ru1- and Ir1@Mo2CS2 catalysts, respectively. This work provides guideline for fabricating and designing highly efficient SACs with superb catalyts using MXene materials.

Co Anchored B36 Cluster as a Novel Single Atom Catalyst for Removing Toxic CO Molecules: A Mechanistic First‐Principles Study

AbstractThe catalytic oxidation of toxic carbon monoxide (CO) into carbon dioxide (CO2) is one of the most significant reactions in heterogeneous catalysis and industrial chemistry. Hence, finding efficient and cost‐effective catalysts for CO oxidation is very critical. In this study, the electronic and catalytic properties of a Co atom incorporated B36 cluster (Co@B36) are investigated by means of first‐principles calculations. The results show that the Co atom can seriously tune the properties of the B36 cluster due to significant hybridization between the 3d states of the Co atom and the B‐2p states of the surrounding B atoms. This induces a significant positive charge on the Co atom, providing an active site for O2 and CO molecules to attack. Furthermore, the well‐known mechanisms for CO oxidation, namely the Eley‐Rideal (ER), Langmuir‐Hinshelwood (LH), termolecular Eley‐Rideal (TER), and new Eley‐Rideal (NER), are taken into account in this work. According to our findings, the LH and TER mechanisms are the most energetically efficient routes for CO oxidation; however, the favored mechanism may be depending on the relative concentrations of CO and O2 molecules in the reaction mixture. The obtained activation energies through the TER and LH mechanisms are also comparable with those reported on noble metals. The findings of this work might help in the design and manufacture of noble‐metal free single atom catalysts for the removal of harmful CO molecules from the environment.

Comparative Study of NO and CO Oxidation Reactions on Single-Atom Catalysts Anchored Graphene-like Monolayer.

Noble metal single-atom catalysts (NM-SACs) anchored at novel graphene-like supports has attracted enormous interests. Gas sensitivity, catalytic activity, and d-band centers of single NM (Pt and Pd) atoms at graphenylene (graphenylene-NM) are investigated using first-principle calculations. The adsorption geometries of gas reactants on graphenylene-NM sheets are analyzed. It is found that the adsorption energies of reactant species on graphenylene-Pt are larger than those on graphenylene-Pd, because the d-band center of the Pt atom is closeser to the Fermi level. The NO and CO oxidation reactions on graphenylene-NM are investigated via four catalytic mechanisms, including Langmuir-Hinshelwood (LH), Eley-Rideal (ER), New ER (NER), and termolecular ER (TER). The results show that the NO and CO oxidations via LH and TER mechanisms can occur owing to the relatively small energy barriers. Moreover, the interaction of 2NO+2CO via ER mechanism is the energetically more favorable reaction. Although the NO oxidation via the NER mechanism has rather low energy barriers, the reaction is unlikely to occur due to the low adsorption energy of O2 compared with CO and NO. This research may provide guidance for exploring the catalytic performance of SACs on graphene-like materials to remove toxic gas molecules.

Non-noble metal single-atom catalyst of Co1/MXene (Mo2CS2) for CO oxidation

MXene is a variety of new two-dimensional (2D) materials with early transition metal carbides, nitrides, and carbonitrides. Quantum chemical studies have been carried out on the geometries, electronic structures, stability and catalytic properties of a non-noble metal single-atom catalyst (SAC) with single Co atom anchored on MXene materials of Mo2CS2. The Co adatom anchored on top of the Mo atom of this MXene is found to be rather stable, and this SAC is appropriate for CO oxidation. The charge transfers from the surface to the adsorbed CO and O2 play a significant role in the activation of these molecules on Co1/Mo2CS2. With this catalyst, the Eley-Rideal (ER), Langmuir-Hinshelwood (LH), and Termolecular Eley-Rideal (TER) mechanisms are explored for CO oxidation. We find that, while all the three mechanisms are feasible at low temperature, Co1/Mo2CS2 possesses higher catalytic activity for CO oxidation through the TER mechanism that features an intriguing OC(OO)CO intermediate (IM) adsorbed on Co single atom. The calculated activation energy barriers of the rate-limiting step are 0.67 eV (TER), 0.78 eV (LH) and 0.88 eV (ER), respectively. The present study illustrates that it is promising to develop and design low-cost, non-noble metal SACs using MXene types of 2D materials.

The coordination of Al on pyridinic-N doped graphene as electrons reservoir for efficiently catalyzing CO oxidization

Single atom catalysts (SACs) have gained paramount attention due to their superior catalytic reactivity. Herein, as the most abundant metal on earth, the aluminum (Al) was used to construct a novel SAC with configuration of Al-GN4 for catalytic oxidation of CO, where a single Al atom was coordinated with four pyridinic nitrogen atoms doped in graphene grids. Four CO catalytic oxidization mechanisms including Eley-Rideal (ER), Langmuir-Hinshelwool (LH), New Eley-Rideal (NER) and termolecular Eley-Rideal (TER) were investigated to explore the catalytic performance of Al-GN4. It was found that the energy barriers of the rate-determining step for ER, LH and NER mechanisms were in the range from 0.41 to 0.59 eV, denoting the high catalytic activity of Al-GN4. It is worthy to note that the CO oxidization via TER mechanism is nearly barrierless although the probability may be low for its high adsorption energy at the initial state. Through detailed electronic structure analysis, an Al-N-C local structure functioning as electrons reservoir for electrons collection and release during adsorption and activation of O2 was proposed. Our results may provide clues for understanding the catalytic performance of SACs, moreover, we expect it will be helpful for designing other SACs with superior activity.

Theoretical study on the catalytic properties of single-atom catalyst stabilised on silicon-doped graphene sheets

ABSTRACTThe stable configurations, electronic structures and catalytic activities of single-atom metal catalyst anchored silicon-doped graphene sheets (3Si-graphene-M, M = Ni and Pd) are investigated by using density functional theory calculations. Firstly, the adsorption stability and electronic property of different gas reactants (O2, CO, 2CO, CO/O2) on 3Si-graphene-M substrates are comparably analysed. It is found that the coadsorption of O2/CO or 2CO molecules is more stable than that of the isolated O2 or CO molecule. Meanwhile, the adsorbed species on 3Si-graphene-Ni sheet are more stable than those on the 3Si-graphene-Pd sheet. Secondly, the possible CO oxidation reactions on the 3Si-graphene-M are investigated through Eley–Rideal (ER), Langmuir–Hinshelwood (LH) and new termolecular Eley–Rideal (TER) mechanisms. Compared with the LH and TER mechanisms, the interaction between 2CO and O2 molecules (O2 + CO → CO3, CO3 + CO → 2CO2) through ER reactions (< 0.2 eV) are an energetically more favourable. These results provide important reference for understanding the catalytic mechanism for CO oxidation on graphene-based catalyst.

Computational mechanistic insights into CO oxidation reaction over Fe decorated C24N24 fullerene

The potential application of a single Fe atom decorated C24N24 fullerene (Fe@C24N24) as a highly active catalyst for the CO oxidation is investigated through the dispersion-corrected DFT calculations. Three different CO oxidation reaction pathways, including the Eley-Rideal (ER), the Langmuir-Hinshelwood (LH) and the termolecular Eley-Rideal (TER) are investigated comparably. Our results indicate that the CO oxidation would like to occur via the TER mechanism owing to its small activation energies. The calculated energy barrier for the rate-determining step of the TER pathway is 0.35 eV. The results reveal that Fe@C24N24 can be regarded as an innovative metal-free catalyst for the low temperature oxidation of toxic CO.

Exploring different reaction mechanisms for oxidation of CO over a single Pd atom incorporated nitrogen-doped graphene: A DFT study

Single-metal catalysts have attracted particular interests in recent years due to their outstanding catalytic activity in CO oxidation reaction. In the present study, periodic DFT calculations are performed to investigate possible reaction mechanisms for oxidation of CO over a single Pd atom incorporated nitrogen-doped graphene. According to our results, the formation energy of a single-vacancy decreases by incorporation of pyridinic nitrogen atoms in graphene. The Pd atom can be stably anchored over the vacancy site, as evidenced by the large energy barriers for diffusion of the Pd atom to its neighboring sites. It is found that the incorporation of nitrogen atoms makes a significant increase in the adsorption energy of O2 and CO molecules over the supported Pd atom. The latter can be attributed to the shift in the bonding states of the Pd towards the Fermi level, which facilitates the charge-transfer from the 4d orbitals of this atom to the 2π∗ orbitals of O2 and CO molecules. The CO oxidation over the Pd atom supported nitrogen-doped graphene can proceed via three different mechanisms; namely, Eley-Rideal (ER), Langmuir-Hinshelwood (LH) and termolecular Eley-Rideal (TER) mechanisms. Our calculations reveal that the TER mechanism is preferred over the LH and ER, due to its smaller activation energy. The CO oxidation via the TER mechanism is a thermodynamically favorable process over the supported Pd atom, due to a large negative change in the Gibbs free energy of this reaction. The findings of this study can be useful to design more efficient single-atom catalysts to remove toxic CO molecules.

A Single Pd Atom Stabilized on Boron‐Vacancy of h‐BN Nanosheet: A Promising Catalyst for CO Oxidation

AbstractThe possible reaction mechanisms for CO catalytic oxidation by O2 molecule on the Pd‐doped hexagonal boron nitride nanosheet (Pd‐BNNS) were studied using first‐principles calculations. The large adsorption energy of the Pd atom over the boron‐vacancy defect of BN nanosheet suggests that Pd‐BNNS could be stable under high temperatures. According to our results, the adsorption of CO over Pd‐BNNS is energetically preferable than that of O2. Three different reaction pathways of the CO oxidation are investigated comparably: the Eley‐Rideal (ER), the Langmuir‐Hinshelwood (LH) and the termolecular Eley‐Rideal (TER). Our results indicate that the CO oxidation reaction would like to take place via the TER mechanism due to its small activation energies. The calculated energy barrier for the rate‐determining step of the latter pathway is only 0.19 eV. Based on electronic structure analysis, such high catalytic activity of Pd‐BNNS can be related to the strong hybridization of the Pd‐4d and CO‐5σ/CO‐2π* states, which effectively activates the adsorbed CO molecules involved in the TER mechanism.

CO Oxidation Catalyzed by a Single Ti Atom Supported on Divacancy Defective Graphene: A Dispersion‐Corrected DFT Study

AbstractWe report a detailed theoretical investigation on the possible reaction mechanisms of CO oxidation catalyzed by a single Ti atom supported on divacancy defective graphene (TiDVG). The reaction between the adsorbed O2 with CO molecules on TiDVG is compared via three different mechanisms, i. e. Eley‐Rideal (ER), Langmuir‐Hinshelwood (LH) and termolecular Eley‐Rideal (TER). According to our results, the energy barrier for the rate determining step of CO + O2 reaction in the TER mechanism is smaller than those of ER and LH ones. This can be attributed to the significant mixing of electronic states of adsorbed CO and O2 at the reaction site, as well as due to a sizable charge‐transfer from the surface to these molecules. On the other hand, the calculated adsorption energies indicate that the coadsorption of O2 and CO molecules is slightly more energetically favored with respect to the coadsorption of two CO molecules. This result together with the relatively small reaction barriers reveal that the LH mechanism is also possible to occur at low temperature. Our results reported here suggest that TiDVG can be regarded as a green, low‐cost and highly active catalyst for CO oxidation at room temperature.

First-principles study of CO catalytic oxidation on Pd-doped single wall boron nitride nanotube

The carbon monoxide (CO) catalytic oxidation reaction is a model reaction which is important in serials of technical and industrial applications. In this study, density functional theory (DFT) is employed to explore the catalytic oxidation of CO on Pd-doped boron nitride nanotube (BNNT). The electronic structures and thermodynamic parameters of CO and O2, which are adsorbed on BNNT substrate with Pd embedded at the N- and B- vacancy, are examined in detail. It is revealed that the BNNT substrate with vacancy strongly stabilizes the Pd adatom. Benefit from the B vacancy defect, the Pd atom binds strongly with BNNT. The interaction energy of 3.74eV is strong enough to prevent the aggregation of Pd atom. With B vacancy, Pd atom accepts extra electron from the substrate, causing O2 to bind stronger than CO molecule. An additional charge is transferred to O2 when CO and O2 are co-adsorbed on the substrate. This additional charge thus strengthens the O2 and CO adsorption and changes the electronic structure properties of the tube. Four proposed CO oxidation mechanisms (Eley–Rideal (ER), Langmuir–Hinshelwood (LH), termolecular Eley–Rideal (TER), and termolecular Langmuir–Hinshelwood (TLH)) are studied by calculating the reaction energy barriers along the minimum-energy pathway. It is found that a large reaction barrier exists in the rate-limiting step of the ER mechanism. It is then suggested that the most probable mechanisms for CO oxidation on Pd doped boron vacancy BNNT (Pd-Bv/BNNT) could be the LH mechanism and the new TER and TLH mechanisms under experimental circumstances.

CO oxidation on single Pd atom embedded defect-graphene via a new termolecular Eley-Rideal mechanism

Single atom catalysts have attracted wide attention due to their high catalytic activity for CO oxidation. We performed density functional theory (DFT) calculations to investigate the various reaction mechanisms of CO oxidation catalyzed by the single Pd atom embedded defect-graphene system as well as the analysis of the structural and electronic properties. It is found that the CO oxidation on Pd-graphene prefers to a new termolecular Eley–Rideal (TER) mechanism rather than the traditional Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanism. In the TER mechanism, the O2 is activated by two adsorbed CO molecules with an energy barrier of 0.08 eV, and the formed OOC-Pd-COO intermediate dissociates into two CO2 molecules synchronously with the energy barrier of 0.29 eV, as the rate-limiting step. Hence, Pd-graphene may serve as the efficient catalysis to CO oxidation.

CO oxidation catalyzed by the single Co atom embedded hexagonal boron nitride nanosheet: a DFT-D study.

A single metal atom stabilized on two dimensional materials (such as graphene and h-BN) exhibits extraordinary activity in the oxidation of CO. The oxidation of CO by molecular O2 on a single cobalt atom embedded in a hexagonal boron nitride monolayer (h-BN) is investigated using first-principles calculations with dispersion-correction. It is found that the single Co atom prefers to reside in a boron vacancy and possesses great stability. There are three mechanisms for CO oxidation: the traditional Eley-Rideal (ER) and Langmuir-Hinshelwood (LH) mechanisms and the termolecular Eley-Rideal (TER) mechanism proposed recently. Given the relatively small reaction barriers of the rate-limiting steps for the ER, LH and TER mechanisms (0.59, 0.55 and 0.41 eV, respectively), all three mechanisms are able to occur at low temperature. The current study may provide useful clues to develop low cost single atom catalysts.