Effects of the cooperative interaction on the diffusion of hydrogen on MgO(100)

Castelli, Ivano E.; Soriga, Stefan Gabriel; Man, Isabela Costinela

doi:10.1063/1.5029329

Cited by 11 publications

(12 citation statements)

References 47 publications

(57 reference statements)

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“…S2). We note that spurious energy lowering due to charge transfer between adsorbates 36,37 is not expected since all adsorbates are electron acceptors. However, H-bonding between fragments could lead to a more favorable adsorption at high-coverage.…”

Section: Taon-terminated (001) Surfacementioning

confidence: 88%

Suitability of Different Sr₂TaO₃N Surface Orientations for Photocatalytic Water Oxidation

Bouri

2019

Chem. Mater.

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Solar water splitting has attracted much attention as a clean and renewable route to produce hydrogen fuel. Since the oxygen evolution half-reaction (OER) requires high overpotentials, much research has focused on finding catalyst materials that minimize this energy loss. Oxynitrides with a layered perovskite structure have the potential to combine the superior photocatalytic properties of layered perovskite oxides with enhanced visible-light absorption caused by the band gap narrowing due to less electronegative nitrogen ions. In this paper, we study the OER on the (001) and (100) surfaces of the layered oxynitride Sr 2 TaO 3 N using density functional theory (DFT) calculations to obtain the OER free energy profiles and to determine the required overpotentials at various sites on each surface. We find that the reconstructed grooved (100) surface is most relevant for photocatalysis due to suitable band-edge positions combined with a low overpotential and good carrier mobility perpendicular to the surface.

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Section: Taon-terminated (001) Surfacementioning

confidence: 88%

Suitability of Different Sr₂TaO₃N Surface Orientations for Photocatalytic Water Oxidation

Bouri

2019

Chem. Mater.

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“…Migration processes of the ions on MgO(P), MgO(F), and MgO(Al + V) surfaces were investigated using DFT , with the generalized gradient approximation (GGA) and the exchange-correlation functional of Perdew and Wang (PW91) . GGA functionals are accurate enough to calculate migration barriers on the MgO surface by considering no charged defects. All calculations were carried out by the QUANTUM ESPRESSO package, − which uses plane waves, periodic boundary conditions, and Vanderbilt ultrasoft pseudopotentials .…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, it is possible to find possible structures at lower energy regions because the proton is binding on fivefoldcoordinated magnesium sites during the migrations (Figure 5). Castelli et al 55 calculated the proton migration after the coadsorption of two noninteracting protons on an MgO perfect-terrace surface. They showed that the paired structure is always energetically more stable, where each proton binds on surface oxygen and magnesium sites to form the donor (covalent H + −O 2− ) and acceptor (noncovalent H − −Mg 2+ ) pair, respectively.…”

Section: Vacancies and Dopingmentioning

confidence: 99%

Proton Migration on Perfect, Vacant, and Doped MgO(001) Surfaces: Role of Dissociation Residual Groups

2018

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Although migration processes on low-coordination surface sites of a magnesium oxide (MgO) surface are important in technological applications including catalysis in gas interfaces, they are not well understood. In particular, hydrated MgO(001) surfaces present charge transfer and ionic transport phenomena that sometimes do not work properly in technological devices. On the other hand, low-coordination surface sites are chemically attractive. Given that defects and adsorbed species can be characterized by the kinetics of surface processes, in this work, we investigated proton mobility pathways produced from the dissociative adsorption of water molecules on different MgO(001) surfaces: a perfect-terrace, with an anionic vacancy, and with an Al-doped + cationic vacancy. For that purpose, we employed density-functional theory with periodic boundary conditions combined with the climbing imaged nudged elastic band method to compute energy barriers. The dissociative adsorption of water molecules on the perfect-terrace surface depends on their state of aggregation; the anionic vacancy was filled with hydroxyl groups, giving rise to co-adsorbed protons, and the cationic vacancy favored the formation of hydroxylated centers, in good agreement with experiment. The doping and vacancies increase the surface dissociation in the absence of co-adsorbed water molecules by decreasing the barriers of proton and hydroxyl formation. For the different surfaces, considering perfect-terrace surface or surface with defects, the water, hydroxyl, and proton species, are the main sources for changing the proton migration barriers. More free surface sites of basic residual groups follow favorable kinetic mobility of protons on MgO and increase the stability of the migration products, as seen in the surface with an anionic vacancy. Therefore, we showed that defects on MgO(001) surfaces may be important in surface proton transport due to the existence of favorable dissociative adsorption mechanisms of water molecules producing specific residual groups needed to lead to most stable migration pathways.

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“…Once H atoms are adsorbed onto a surface, NQEs can also be important to how they diffuse across it. The role of NQEs in H atom diffusion has been extensively studied on a wide variety of surfaces [115,121,[141][142][143][144][145][146]. Here, we focus on work that we have recently been involved in to understand H atom diffusion across atomically-flat metal surfaces.…”

Section: Diffusion Of Atomic Hydrogenmentioning

confidence: 99%

“…The unusually broad barriers are found on surfaces (see also refs. [145,146]) partly because of the very large mismatch in size between the small H atom and the relatively large surface atoms of the lattice. Such barriers have also been seen for magnetic transitions [157].…”

Section: Diffusion Of Atomic Hydrogenmentioning

confidence: 99%

The quantum nature of hydrogen

Fang

Chen

Feng

et al. 2019

International Reviews in Physical Chemistry

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Hydrogen is the most abundant element. It is also the most quantum, in the sense that quantum tunnelling, quantum delocalisation, and zero-point motion can be important. For practical reasons most computer simulations of materials have not taken such effects into account, rather they have treated nuclei as classical particles. However, thanks to methodological developments over the last few decades, nuclear quantum effects can now be treated in complex materials. Here we discuss our studies on the role nuclear quantum effects play in hydrogen containing systems. We give examples of how the quantum nature of the nuclei has a significant impact on the location of the boundaries between phases in high pressure condensed hydrogen. We show how nuclear quantum effects facilitate the dissociative adsorption of molecular hydrogen on solid surfaces and the diffusion of atomic hydrogen across surfaces. Finally, we discuss how nuclear quantum effects alter the strength and structure of hydrogen bonds, including those in DNA. Overall these studies demonstrate that nuclear quantum effects can manifest in different, interesting, and non-intuitive ways. Whilst historically it has been difficult to know in advance what influence nuclear quantum effects will have, some of the important conceptual foundations have now started to emerge.

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Effects of the cooperative interaction on the diffusion of hydrogen on MgO(100)

Cited by 11 publications

References 47 publications

Suitability of Different Sr₂TaO₃N Surface Orientations for Photocatalytic Water Oxidation

Suitability of Different Sr₂TaO₃N Surface Orientations for Photocatalytic Water Oxidation

Proton Migration on Perfect, Vacant, and Doped MgO(001) Surfaces: Role of Dissociation Residual Groups

The quantum nature of hydrogen

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Effects of the cooperative interaction on the diffusion of hydrogen on MgO(100)

Cited by 11 publications

References 47 publications

Suitability of Different Sr2TaO3N Surface Orientations for Photocatalytic Water Oxidation

Suitability of Different Sr2TaO3N Surface Orientations for Photocatalytic Water Oxidation

Proton Migration on Perfect, Vacant, and Doped MgO(001) Surfaces: Role of Dissociation Residual Groups

The quantum nature of hydrogen

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Suitability of Different Sr₂TaO₃N Surface Orientations for Photocatalytic Water Oxidation

Suitability of Different Sr₂TaO₃N Surface Orientations for Photocatalytic Water Oxidation