Theoretical Investigation of the Mechanism of the Water–Gas Shift Reaction on Cobalt@Gold Core–Shell Nanocluster

Wu, Sheng-Ke; Lin, Ren-Jie; Jang, Soonming; Chen, Hui-Lung; Wang, Shih-Min; Li, Fengyin

doi:10.1021/jp408517m

Cited by 13 publications

(3 citation statements)

References 99 publications

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“…The revealed mechanism of the NiIr-catalyzed CO oxidation mirrors the water–gas shift (WGS) reaction. WGS reactions catalyzed by metal carbonyl complexes have been studied experimentally, − and details of the mechanism have also been elucidated by theoretical investigations. − , The proposed mechanisms both involve formation of metallocarboxylic acids followed by decarboxylation to afford hydride complexes.…”

Section: Resultsmentioning

confidence: 99%

Selective Oxidation of H₂ and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

2020

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One of the challenges in utilizing hydrogen gas (H 2 ) as a sustainable fossil fuel alternative is the inhibition of H 2 oxidation by carbon monoxide (CO), which is involved in the industrial production of H 2 sources. To solve this problem, a catalyst that selectively oxidizes either CO or H 2 or one that co-oxidizes H 2 and CO is needed. Recently, a NiIr catalyst [Ni II Cl(X)Ir III Cl(η 5 -C 5 Me 5 )], (X = N,N′dimethyl-3,7-diazanonane-1,9-dithiolate), which efficiently and selectively oxidizes either H 2 or CO depending on the pH, has been developed (Angew. Chem. Int. Ed. 2017, 56, 9723−9726). In the present work, density functional theory (DFT) calculations are employed to elucidate the pH-dependent reaction mechanisms of H 2 and CO oxidation catalyzed by this NiIr catalyst. During H 2 oxidation, our calculations suggest that dihydrogen binds to the Ir center and generates an Ir(III)−dihydrogen complex, followed by subsequent isomerization to an Ir(V)−dihydride species. Then, a proton is abstracted by a buffer base, CH 3 COO − , resulting in the formation of a hydride complex. The catalytic cycle completes with electron transfer from the hydride complex to a protonated 2,6-dichlorobenzeneindophenol (DCIP) and a proton transfer from the oxidized hydride complex to a buffer base. The CO oxidation mechanism involves three distinct steps, i.e., (1) formation of a metal carbonyl complex, (2) formation of a metallocarboxylic acid, and (3) conversion of the metallocarboxylic acid to a hydride complex. The formation of the metallocarboxylic acid involves nucleophilic attack of OH − to the carbonyl-C followed by a large structural change with concomitant cleavage of the Ir−S bond and rotation of the COOH group along the NiIr axis. During the conversion of the metallocarboxylic acid to the hydride complex, intramolecular proton transfer followed by removal of CO 2 leads to the formation of the hydride complexes. In addition, the barrier heights for the binding of small molecules (H 2 , OH − , H 2 O, and CO) to Ir were calculated, and the results indicated that dissociation from Ir is a faster process than the binding of H 2 O and H 2 . These calculations indicate that H 2 oxidation is inhibited by CO and OH − and thus prefers acidic conditions. In contrast, the CO oxidation reactions occur more favorably under basic conditions, as the formation of the metallocarboxylic acid involves OH − attack to a carbonyl-C and the binding of OH − to Ni largely stabilizes the triplet spin state of the complex. Taken together, these calculations provide a rationale for the experimentally observed pH-dependent, selective oxidations of H 2 and CO.

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Section: Resultsmentioning

confidence: 99%

Selective Oxidation of H₂ and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

2020

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“…The exchange-correlation energies were calculated via the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional [85]. The valance electrons were described by 5d 10 6s 1 for Au, 4d 9 5s 1 for Pd, 2s 2 2p 4 for O and 2s 2 2p 2 for C. We used a 25 Å×25 Å×25 Å cubic supercell for all the calculations, as reported by Lin et al [86,87]. An energy cutoff of 400 eV was chosen for the plane wave expansion of the electronic eigenfunctions.…”

Section: Theoretical Methodsmentioning

confidence: 99%

Catalytic mechanism and bonding analyses of Au-Pd single atom alloy (SAA): CO oxidation reaction

Baskaran

Wang

et al. 2020

Sci. China Mater.

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Single-atom catalysts (SACs), including metalmetal-bonded bimetallic ones named single-atom alloys (SAAs), have aroused significant interest in catalysis. In this article, the catalytic mechanism and bonding analysis of CO oxidation reaction on bimetallic gold-palladium (Au-Pd) model of single atom alloy Au 37 Pd 1 are investigated by using quantum chemical calculations. The molecular geometries and adsorbate/substrate binding energies of CO@Au-Pd, O 2 @Au-Pd and CO/O 2 @Au-Pd configurations are identified. The core-shell structure is confirmed to be the most stable structure for Au-Pd SAA, where the Pd atom prefers to situate at the core site. Charge transfer from the Pd atom to the Au atoms has been confirmed to stabilize the structure. According to the binding energy and chemical bonding analysis, both CO and O 2 prefer to bind to the Pd atom at the hex site with low coordination number. The formation of new co-adsorption species is identified, in which vertical and parallel bridging adsorptions of CO and O 2 on the Au-Pd bonds are observed. CO oxidation on Au-Pd SAA is found to be feasible with low energy barriers and follows the Langmuir-Hinshewood (L-H) mechanism. Our work offers insights into the significant role of single atom of the SAAs in catalytic reactions and can provide evidence for designing new SAAs with high-performance catalytic activities.

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“…Their study revealed that the core–shell nanoclusters are highly active for CO oxidation, compared to Au(1 1 1) and Au(3 2 1) surfaces. Wu and co‐workers compared the reaction mechanism of the water gas shift reaction catalyzed by a Co 6 @Au 32 nanocluster with that catalyzed by the Au 38 cluster by employing DFT calculations . They found that the core Co atoms can control the geometry structure of the surface Au atoms and the electronic structure near the Fermi level indicating the foreign core could play an important role in the catalytic reactions.…”

Section: Introductionmentioning

confidence: 99%

A DFT Insight into Hashmi Phenol Synthesis Catalyzed by M₆@Au₃₂ (M=Ag, Cu, Pd, Pt, Ru, Rh) Core–Shell Nanoclusters

et al. 2016

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The Hashmi phenol synthesis reaction (the ω‐alkynylfuran cycloisomerization) catalyzed by the M6@Au32 (M=Ag, Cu, Pd, Pt, Ru, and Rh) core–shell nanoclusters was investigated systematically. The 5‐exo Friedel–Crafts‐type mechanism of the ω‐alkynylfuran cycloisomerization on the six core–shell nanoclusters was analyzed in details. The adsorption property and catalytic activity of the Au38 nanocluster could be effectively tuned by the substitution of the core Au atoms. The adsorption properties of alkynes on core–shell and Au38 clusters depended on four factors, including the numbers of unoccupied and occupied d orbitals, orientation of d orbital and d‐bonding down‐shift. Compared with the Au38 cluster, the core–shell nanoclusters could cause larger changes in the interaction energies between the substrate and cluster fragments, which are beneficial for facilitating the cyclization step and the ring closing of the dienone carbene–gold intermediate. In addition, according to the calculated results, the catalytic activity of Au38 can be tuned by substitution of the core gold atoms.

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Theoretical Investigation of the Mechanism of the Water–Gas Shift Reaction on Cobalt@Gold Core–Shell Nanocluster

Cited by 13 publications

References 99 publications

Selective Oxidation of H₂ and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

Selective Oxidation of H₂ and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

Catalytic mechanism and bonding analyses of Au-Pd single atom alloy (SAA): CO oxidation reaction

A DFT Insight into Hashmi Phenol Synthesis Catalyzed by M₆@Au₃₂ (M=Ag, Cu, Pd, Pt, Ru, Rh) Core–Shell Nanoclusters

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Theoretical Investigation of the Mechanism of the Water–Gas Shift Reaction on Cobalt@Gold Core–Shell Nanocluster

Cited by 13 publications

References 99 publications

Selective Oxidation of H2 and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

Selective Oxidation of H2 and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

Catalytic mechanism and bonding analyses of Au-Pd single atom alloy (SAA): CO oxidation reaction

A DFT Insight into Hashmi Phenol Synthesis Catalyzed by M6@Au32 (M=Ag, Cu, Pd, Pt, Ru, Rh) Core–Shell Nanoclusters

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Selective Oxidation of H₂ and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

Selective Oxidation of H₂ and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

A DFT Insight into Hashmi Phenol Synthesis Catalyzed by M₆@Au₃₂ (M=Ag, Cu, Pd, Pt, Ru, Rh) Core–Shell Nanoclusters