What Is the Real State of Single-Atom Catalysts under Electrochemical Conditions—From Adsorption to Surface Pourbaix Plots?

Dobrota, Ana S.; Đokić, Tanja; Skorodumova, Natalia V.; Mentus, Slavko; Pašti, Igor A.

doi:10.3390/catal11101207

Cited by 7 publications

(4 citation statements)

References 52 publications

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“…Dobrota et al investigated by means of DFT the nature of various TM atoms in a graphene monovacancy finding that the metal centers are covered with H, O, or OH groups at any potential or pH in the water thermodynamic stability region. 50 A similar conclusion was reached by the same group for TM atoms stabilized in N-doped graphene. 51 Besides formation of stable complexes at the TM centers, demetalation is a serious problem in electrochemical reactions, but relatively few theoretical studies have been dedicated to this problem.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Things are even more complicated in electrochemical reactions where solvent, pH, and applied voltage can result in a variety of behaviors of the metal species, including demetalation. Dobrota et al investigated by means of DFT the nature of various TM atoms in a graphene monovacancy finding that the metal centers are covered with H, O, or OH groups at any potential or pH in the water thermodynamic stability region . A similar conclusion was reached by the same group for TM atoms stabilized in N-doped graphene .…”

Section: Introductionmentioning

confidence: 99%

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Predicting the Stability of Single-Atom Catalysts in Electrochemical Reactions

Di Liberto,

Giordano,

Pacchioni

2023

ACS Catal.

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The attention toward single-atom catalysts (SACs) for electrochemical processes is growing at an impressive pace. Electronic structure calculations play an important role in this race by providing proposals of potentially relevant catalysts based on screening studies or on the identification of descriptors of the chemical activity. So far, almost all of these predictions ignore a crucial aspect in the design of a catalyst: its stability. We propose a simple yet general first-principles approach to predict the stability of SACs under working conditions of pH and applied voltage. This is based on the construction of a thermodynamic cycle, where part of the information is taken from experiment and the rest from density functional theory (DFT) calculations. In particular, we make use of the formalism of Pourbaix diagrams to investigate the stability of SACs in reductive or oxidative conditions and we identify those that show a pronounced tendency to dissolve or to form other chemical species. Applying the procedure to four transition metal atoms, Cr, Mn, Fe, and Co, and to three supports, N-doped graphene, carbon nitride, and covalent organic frameworks, we show that a key factor in determining the final stability is the binding energy of the free metal atom to the support. The results show that several potentially very good catalysts in key electrochemical reactions are, in fact, dramatically prone to dissolution or transformation in other chemical species, suggesting that every prediction of the SAC’s catalytic activity should be accompanied by a parallel investigation of the stability.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Predicting the Stability of Single-Atom Catalysts in Electrochemical Reactions

Di Liberto,

Giordano,

Pacchioni

2023

ACS Catal.

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“…However, in the case of SACs, once an adsorbate/ligand attaches to the active center, it is completely changed. Hence, as the matrix cannot be separated from the active metal atoms, the same holds true for any adsorbate/ligand attached to the original active site [ 22 ].…”

Section: Introductionmentioning

confidence: 99%

The Local Coordination Effects on the Reactivity and Speciation of Active Sites in Graphene-Embedded Single-Atom Catalysts over Wide pH and Potential Range

et al. 2022

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Understanding the catalytic performance of different materials is of crucial importance for achieving further technological advancements. This especially relates to the behaviors of different classes of catalysts under operating conditions. Here, we analyzed the effects of local coordination of metal centers (Mn, Fe, Co) in graphene-embedded single-atom catalysts (SACs). We started with well-known M@N4-graphene catalysts and systematically replaced nitrogen atoms with oxygen or sulfur atoms to obtain M@OxNy-graphene and M@SxNy-graphene SACs (x + y = 4). We show that local coordination strongly affects the electronic structure and reactivity towards hydrogen and oxygen species. However, stability is even more affected. Using the concept of Pourbaix plots, we show that the replacement of nitrogen atoms in metal coordinating centers with O or S destabilized the SACs towards dissolution, while the metal centers were easily covered by O and OH, acting as additional ligands at high anodic potentials and high pH values. Thus, not only should local coordination be considered in terms of the activity of SACs, but it is also necessary to consider its effects on the speciation of SAC active centers under different potentials and pH conditions.

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“…However, in the case of SACs, once an adsorbate/ligand attaches to the active center, it is completely changed. Hence, as the matrix cannot be separated from the active metal atoms, the same holds for any adsorbate/ligand attached to the original active site [22].…”

Section: Introductionmentioning

confidence: 99%

The Local Coordination Effects on the Reactivity and Speciation of Active Sites in Graphene-Embedded Single-Atom Catalysts Over Wide pH and Potential Range

S.¹,

Dobrota²,

Skorodumova³

et al. 2022

Preprint

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Understanding the catalytic performance of different materials is of crucial importance for further technological advancements. This especially relates to the behavior of different classes of catalysts under operating conditions. Here we analyze the effects of local coordination of metal centers (Mn, Fe, Co) in graphene-embedded Single-Atom Catalysts (SACs). We have started from well-known M@N4-graphene catalysts and systematically replaced nitrogen atoms with oxygen or sulfur atom to obtain M@OxNy-graphene and M@SxNy-graphene SACs (x+y=4). We show that local coordination strongly affects the electronic structure and the reactivity towards hydrogen and oxygen species. However, the stability is even more affected. Using the concept of Pourbaix plots, we show that the replacement of nitrogen atoms coordinating metal center with O or S destabilizes SACs towards the dissolution, while the metal centers get easily covered by O and OH acting as additional ligands at high anodic potentials and high pH values. Thus, not only should local coordination be considered in terms of the activity of SACs, but it is also necessary to consider its effects on the speciation of SACs' active centers under different potential and pH conditions.

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What Is the Real State of Single-Atom Catalysts under Electrochemical Conditions—From Adsorption to Surface Pourbaix Plots?

Cited by 7 publications

References 52 publications

Predicting the Stability of Single-Atom Catalysts in Electrochemical Reactions

Predicting the Stability of Single-Atom Catalysts in Electrochemical Reactions

The Local Coordination Effects on the Reactivity and Speciation of Active Sites in Graphene-Embedded Single-Atom Catalysts over Wide pH and Potential Range

The Local Coordination Effects on the Reactivity and Speciation of Active Sites in Graphene-Embedded Single-Atom Catalysts Over Wide pH and Potential Range

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