Lowering the C-H Bond Activation Barrier of Methane Using SAC@Cu(111): A Periodic DFT Investigations

Methane has long captured the world's spotlight for being the simplest and yet one of the most notorious hydrocarbon. Exploring its potential to be converted into value added products has raised a compelling interest. In the present work, we have studied the efficiency of Single-Atom Catalysts (SACs) for methane activation employing Density Functional Theory (DFT). The Climbing Image-Nudged Elastic Bond (CI-NEB) method is used in tandem with the Improved Dimer (ID) method to determine the minimum energy pathway for the first C-H bond dissociation of methane. Our study reported that the transition-metal doped Cu(111) surfaces enhance adsorption, activate C-H bond, and reduce activation barrier for first C-H bond cleavage of methane. The results suggest Ru/Co/Rh doped Cu(111) as promising candidates for methane activation with minimal activation barrier and less endothermic reaction. For these SACs, the calculated activation barriers for first C-H bond cleavage are 0.17 eV, 0.24 eV, and 0.26 eV respectively, which is substantially lower than 1.13 eV, the activation barrier for Cu(111).

Download Full-text

Regulating coordination number in atomically dispersed Pt species on defect-rich graphene for n-butane dehydrogenation reaction

Nature Communications ◽

10.1038/s41467-021-22948-w ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Xiaowen Chen ◽

Mi Peng ◽

Xiangbin Cai ◽

Yunlei Chen ◽

Zhimin Jia ◽

...

Keyword(s):

Coordination Number ◽

Density Functional ◽

Activation Barrier ◽

Density Functional Theory Calculation ◽

Catalytic Performance ◽

Atomic Level ◽

Metal Nanoparticle ◽

Single Atom ◽

Nano Structure ◽

Theory Calculation

AbstractMetal nanoparticle (NP), cluster and isolated metal atom (or single atom, SA) exhibit different catalytic performance in heterogeneous catalysis originating from their distinct nanostructures. To maximize atom efficiency and boost activity for catalysis, the construction of structure–performance relationship provides an effective way at the atomic level. Here, we successfully fabricate fully exposed Pt3 clusters on the defective nanodiamond@graphene (ND@G) by the assistance of atomically dispersed Sn promoters, and correlated the n-butane direct dehydrogenation (DDH) activity with the average coordination number (CN) of Pt-Pt bond in Pt NP, Pt3 cluster and Pt SA for fundamentally understanding structure (especially the sub-nano structure) effects on n-butane DDH reaction at the atomic level. The as-prepared fully exposed Pt3 cluster catalyst shows higher conversion (35.4%) and remarkable alkene selectivity (99.0%) for n-butane direct DDH reaction at 450 °C, compared to typical Pt NP and Pt SA catalysts supported on ND@G. Density functional theory calculation (DFT) reveal that the fully exposed Pt3 clusters possess favorable dehydrogenation activation barrier of n-butane and reasonable desorption barrier of butene in the DDH reaction.

Download Full-text

Metal and Ligand Effects on Coordinated Methane pKa. Direct Correlation with the Methane Activation Barrier

10.26434/chemrxiv.12323726 ◽

2020 ◽

Author(s):

Amy Guan ◽

Ivy Liang ◽

Christopher Zhou ◽

Thomas Cundari

Keyword(s):

Free Energy ◽

Direct Relationship ◽

Activation Barrier ◽

Methane Activation ◽

Coupled Cluster ◽

Activation Barriers ◽

Ligand Effects ◽

3D Metals ◽

Cluster Methods ◽

The Impact

DFT and coupled cluster methods were used to investigate the impact of 3d metals and ligands upon the acidity and activation of coordinated methane C–H bonds. A strong, direct relationship was established between the pKa of coordinated methane and the subsequent free energy barriers to H3C–H activation. The few outliers to this relationship indicated other factors– such as thermodynamic stability of the product and ligand-metal coordination type – also impacted the methane activation barrier (dG‡). High variations in the activation barriers and pKa values were found with a range of 34.8 kcal/mol for the former and 28.6 pKa units for the latter. Clear trends among specific metals and ligands were also derived; specific metals, such as CoI, as well as Lewis and p-acids consistently yielded higher acidity for the ligated methane and hence lower dG‡.

Download Full-text

Stability of heterogeneous single-atom catalysts: a scaling law mapping thermodynamics to kinetics

npj Computational Materials ◽

10.1038/s41524-020-00411-6 ◽

2020 ◽

Vol 6 (1) ◽

Author(s):

Ya-Qiong Su ◽

Long Zhang ◽

Yifan Wang ◽

Jin-Xun Liu ◽

Valery Muravev ◽

...

Keyword(s):

Metal Atom ◽

Density Functional ◽

Activation Barrier ◽

Scaling Law ◽

Precious Metals ◽

Catalytic Performance ◽

Single Atom ◽

Atom Diffusion ◽

Computational Screening ◽

Metal Support

Abstract Heterogeneous single-atom catalysts (SACs) hold the promise of combining high catalytic performance with maximum utilization of often precious metals. We extend the current thermodynamic view of SAC stability in terms of the binding energy (Ebind) of single-metal atoms on a support to a kinetic (transport) one by considering the activation barrier for metal atom diffusion. A rapid computational screening approach allows predicting diffusion barriers for metal–support pairs based on Ebind of a metal atom to the support and the cohesive energy of the bulk metal (Ec). Metal–support combinations relevant to contemporary catalysis are explored by density functional theory. Assisted by machine-learning methods, we find that the diffusion activation barrier correlates with (Ebind)2/Ec in the physical descriptor space. This diffusion scaling-law provides a simple model for screening thermodynamics to kinetics of metal adatom on a support.

Download Full-text

On the role of the surface oxygen species during A–H (A = C, N, O) bond activation: a density functional theory study

Chemical Communications ◽

10.1039/c4cc08658a ◽

2015 ◽

Vol 51 (13) ◽

pp. 2621-2624 ◽

Cited By ~ 28

Author(s):

Jong Suk Yoo ◽

Tuhin S. Khan ◽

Frank Abild-Pedersen ◽

Jens K. Nørskov ◽

Felix Studt

Keyword(s):

Density Functional ◽

Bond Activation ◽

Bond Cleavage ◽

Oxygen Species ◽

Final States ◽

Surface Oxygen ◽

Density Functional Theory Study ◽

Reaction Energy ◽

Functional Theory

During A–H (A = C, N, O) bond cleavage on O* or OH* pre-covered (111) surfaces, the oxygen species play the role of modifying the reaction energy by changing the species involved in the initial and final states of the reaction.

Download Full-text

Facile formation of azines from reactions of singlet methylene and dimethylcarbene with precursor diazirines: theoretical explorations

Canadian Journal of Chemistry ◽

10.1139/v99-012 ◽

1999 ◽

Vol 77 (5-6) ◽

pp. 540-549 ◽

Cited By ~ 7

Author(s):

Gennady V Shustov ◽

Michael TH Liu ◽

K N Houk

Keyword(s):

Density Functional Theory ◽

Ab Initio ◽

Ring Opening ◽

Density Functional ◽

Activation Barrier ◽

Thermal Reaction ◽

Orbital Theory ◽

Functional Theory ◽

Activation Barriers ◽

Singlet Methylene

The reactions of the singlet methylene (1a) and dimethylcarbene (1b), with their diazirine precursors, diazirine (2a), and dimethyldiazirine (2b), have been studied theoretically using ab initio and density functional theory. The reaction has no activation barriers for the parent system (1a + 2a) and proceeds via a reactive complex and a transition state with a small negative enthalpy of activation Δ Hnot =298 = -1.1 kcal mol-1, ΔSnot =298 = -34.4 cal mol-1 K-1, ΔG°298 = 9.2 kcal mol-1) for the dimethyl derivatives (1b + 2b). The formation of N-methylene diazirinium ylides (3a,b) is exothermic by 64-80 kcal mol-1. The isomer, 1,3-diazabicyclo[1.1.0]butane (4a), is more stable (5-12 kcal mol-1) than isomer 3a, but can neither be formed by direct thermal reaction of 1a with 2a nor undergo the direct rearrangement into formaldazine (5a). The rearrangement of ylides 3a,b into azines 5a,b proceeds by conrotatory C3-N1 ring opening. The predicted activation barrier of ca. 15 kcal mol-1 for the ring opening in ylide 3b is in excellent agreement with experimental data. The formation of pyridinium ylides from carbenes and pyridine is also studied.Key words: diazirinium ylide, ab initio MO (molecular orbital) theory, density functional theory, pyridinium ylide, CIS (singles configuration interaction) transition energies.

Download Full-text

“Soft” oxidative coupling of methane to ethylene: Mechanistic insights from combined experiment and theory

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2012666118 ◽

2021 ◽

Vol 118 (23) ◽

pp. e2012666118

Author(s):

Shanfu Liu ◽

Sagar Udyavara ◽

Chi Zhang ◽

Matthias Peter ◽

Tracy L. Lohr ◽

...

Keyword(s):

Oxidative Coupling ◽

Methane Conversion ◽

Density Functional ◽

Activation Barrier ◽

Oxidative Coupling Of Methane ◽

Methane Activation ◽

Kinetic Isotope ◽

Mechanistic Analysis ◽

Adsorbed Sulfur ◽

Product Forms

The oxidative coupling of methane to ethylene using gaseous disulfur (2CH4 + S2 → C2H4 + 2H2S) as an oxidant (SOCM) proceeds with promising selectivity. Here, we report detailed experimental and theoretical studies that examine the mechanism for the conversion of CH4 to C2H4 over an Fe3O4-derived FeS2 catalyst achieving a promising ethylene selectivity of 33%. We compare and contrast these results with those for the highly exothermic oxidative coupling of methane (OCM) using O2 (2CH4 + O2 → C2H4 + 2H2O). SOCM kinetic/mechanistic analysis, along with density functional theory results, indicate that ethylene is produced as a primary product of methane activation, proceeding predominantly via CH2 coupling over dimeric S–S moieties that bridge Fe surface sites, and to a lesser degree, on heavily sulfided mononuclear sites. In contrast to and unlike OCM, the overoxidized CS2 by-product forms predominantly via CH4 oxidation, rather than from C2 products, through a series of C–H activation and S-addition steps at adsorbed sulfur sites on the FeS2 surface. The experimental rates for methane conversion are first order in both CH4 and S2, consistent with the involvement of two S sites in the rate-determining methane C–H activation step, with a CD4/CH4 kinetic isotope effect of 1.78. The experimental apparent activation energy for methane conversion is 66 ± 8 kJ/mol, significantly lower than for CH4 oxidative coupling with O2. The computed methane activation barrier, rate orders, and kinetic isotope values are consistent with experiment. All evidence indicates that SOCM proceeds via a very different pathway than that of OCM.

Download Full-text

Theoretical study of dimethylcarbonate production by urea alcoholysis

Butlerov Communications ◽

10.37952/roi-jbc-01/20-62-4-38 ◽

2020 ◽

Vol 62 (4) ◽

pp. 38-50

Author(s):

Nikita I. Kurshev ◽

Keyword(s):

Zinc Oxide ◽

Density Functional ◽

Dimethyl Carbonate ◽

Activation Barrier ◽

Equilibrium Constants ◽

Density Functional Method ◽

Intermediate Formation ◽

Functional Method ◽

Activation Barriers ◽

The Difference

Using the density functional method М06, the mechanisms of non-catalytic reactions of transesterification of urea with methanol with the formation of dimethyl carbonate, as well as in catalysis with zinc oxide and acetate, were studied. The transesterification proceeds stepwise with the intermediate formation of methyl carbamate. The non-catalytic process of transesterification of urea with methanol proceeds by the mechanism of nucleophilic SN2 substitution and is accompanied by the formation of pre-reaction complexes, which through synchronous transition states turn into post-reaction complexes, decomposing into ammonia and methyl carbamate in the first stage and dimethyl carbonate in the second. It has been established that methanol associates can take part in these reactions. Their participation is preferable both kinetically and thermodynamically. An analysis of the equilibrium constants of the reaction of urea with methanol at various temperatures showed that in a wide temperature range their values remain large in the first stage – the formation of methyl carbamate and become significantly reversible in the second – the conversion of methyl carbamate to dimethyl carbonate. Reactions involving acetate and zinc oxide proceed through the same stages as non-catalytic interactions. In the case of zinc acetate catalyzed reactions, if methanol monomer is involved in the reaction, the reaction of formation of methyl carbamate has a lower activation barrier compared to the reaction of conversion of methyl carbamate to dimethyl carbonate. If a methanol dimer is involved in the reaction, both reactions have a practically equal activation barrier. In the case of zinc oxide catalyzed interactions, reactions involving a methanol dimer were not detected. The participation of the catalyst leads to a significant decrease in activation barriers, and a more significant decrease occurs in the case of catalysis with zinc oxide. The reason for the different catalytic activity, in our opinion, is the difference in the charges on the urea carbon atom in the pre-reaction complexes.

Download Full-text

Metal and Ligand Effects on Coordinated Methane pKa. Direct Correlation with the Methane Activation Barrier

10.26434/chemrxiv.12323726.v1 ◽

2020 ◽

Author(s):

Amy Guan ◽

Ivy Liang ◽

Christopher Zhou ◽

Thomas Cundari

Keyword(s):

Free Energy ◽

Direct Relationship ◽

Activation Barrier ◽

Methane Activation ◽

Coupled Cluster ◽

Activation Barriers ◽

Ligand Effects ◽

3D Metals ◽

Cluster Methods ◽

The Impact

Download Full-text

Hydrogen transfer reaction: Bond formation and bond cleavage through the eyes of interacting quantum atoms

Journal of the Serbian Chemical Society ◽

10.2298/jsc190226034m ◽

2019 ◽

Vol 84 (8) ◽

pp. 891-900

Author(s):

Branislav Milovanovic ◽

Mihajlo Etinski ◽

Milena Petkovic

Keyword(s):

Hydrogen Atom ◽

Density Functional ◽

Hydrogen Transfer ◽

Bond Cleavage ◽

Bond Formation ◽

Minimum Energy ◽

Fragment Analysis ◽

Interacting Quantum Atoms ◽

Methoxy Radical ◽

The One

Hydrogen transfer from hydroquinone to the methoxy radical was studied using the density functional theory. The energy decomposition technique, interacting quantum atoms, was employed for a detailed investigation of the changes that the bonds of interest go through along the minimum energy path in the vicinity of the transition state. The whole system was divided either into two or three fragments. The two-fragment analysis enabled investigation of the bond that is formed or the one that is cleaved by defining the fragments as reactants and as products, respectively. The three-fragment analysis (the fragments being semiquinone, hydrogen atom and methoxy radical) was used for the simultaneous analysis of the two phenomena, bond cleavage and bond formation. Additionally, it enabled the interaction between the particle that donates the hydrogen atom and the one that accepts it to be investigated. This interaction is characterized by attractive non-classical and repulsive classical interactions. It was demonstrated that the transferring hydrogen atom undergoes the most pronounced energy changes and gives the largest contribution to the deformation energy.

Download Full-text

High-Throughput Screening Single-Atom Alloy for Electroreduction of Dinitrogen to Ammonia

10.26434/chemrxiv.13546634 ◽

2021 ◽

Author(s):

Guokui Zheng ◽

Ziqi Tian ◽

Xingwang Zhang ◽

Liang Chen ◽

Xu Qian ◽

...

Keyword(s):

High Throughput Screening ◽

Density Functional ◽

Ammonia Synthesis ◽

Density Functional Theory Calculations ◽

Reduction Reaction ◽

Single Atom ◽

Functional Theory ◽

Metal Doped ◽

Single Atom Alloy ◽

Single Atom Alloys

Exploring electrocatalyst with high activity, selectivity and stability is essential for development of applicable electrocatalytic ammonia synthesis technology. By performing density functional theory calculations, we systematically investigated a series of transition-metal doped Au-based single atom alloys (SAAs) as promising electrocatalysts for nitrogen reduction reaction (NRR). For Au-based electrocatalyst, the first hydrogenation step (*N2→*NNH) normally determines the limiting potential of the overall reaction process. Compared with pristine Au(111) surface, introducing single atom can significantly enhance the binding strength of N2, leading to decreased energy barrier of the key step, i.e., ΔG(*N2→*NNH). According to simulation results, three descriptors were proposed to describe ΔG(*N2→*NNH), including ΔG(*NNH), d-band center, and . Eight doped elements (Ti, V, Nb, Ru, Ta, Os, W, and Mo) were initially screened out with limiting potential ranging from -0.75V to -0.30 V. Particularly, Mo- and W-doped systems possess the best activity with limiting potentials of -0.30 V, respectively. Then the intrinsic relationship between structure and the potential performance was further analyzed by using machine-learning. The selectivity, feasibility, stability of these candidates were also evaluated, confirming that SAA containing Mo, Ru ,Ta, and W could be outstanding NRR electrocatalysts. This work not only broadens the understating of SAA application in electrocatalysis, but also devotes to the discovery of novel NRR electrocatalysts.

Download Full-text