Hydrogen complexes on single atom alloys: classical chemisorption <i>versus</i> coordination chemistry

Barlocco, Ilaria; Liberto, Giovanni Di; Pacchioni, Gianfranco

doi:10.1039/d3cy00609c

Cited by 6 publications

(4 citation statements)

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“…Finally, the adsorption of one H atom exceeding the monolayer on Pt1 shows that the adatom is not an active center, even after adsorbing more than one extra H. Indeed, the adsorption energy of an additional H is -79.4 kJ mol -1 , that of the second H atom is -57.1 kJ mol -1 , while the adsorption of the third atom exceeding the monolayer is unfavorable. This is consistent with reports by Pacchioni and co-workers, which suggest that Pt single atom catalysts are not particularly active for HER [35,36]. suggesting that defective sites significantly enhance the catalytic activity of ruthenium for HER.…”

Section: Defective M10 M7 and M1 Slabssupporting

confidence: 92%

“…Several, non-mutually exclusive strategies have been outlined to reduce the catalyst cost [15,16], including: a) the use of Earth-abundant alternatives to platinum [15,[17][18][19][20][21][22][23][24][25] and b) the design of new materials with lower noble metal content [16,19,[26][27][28][29][30][31][32]. In the struggle for Pt-free catalysts [14], advances in nanofabrication allow for finely-tuned catalysts to be designed, aided by the extensive research into single-atom catalysts (SAC) [28,30,31,[33][34][35] and SAC-alloys [36], edged surfaces [37] and nanoparticles [38]. In this context, despite also being a noble metal, ruthenium has attracted significant attention [12,39,40].…”

Section: Introductionmentioning

confidence: 99%

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Different role of ruthenium and platinum defective sites on the catalytic activity for the hydrogen evolution reaction

Fenoll,

Sodupe,

Solans Monfort

2024

Preprint

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The reduction of protons to H2 (the hydrogen evolution reaction, or HER) is one of the two half reaction of water electrolysis. It produces H2 that can be used as energy vector or sustainable feedstock for other compounds. Platinum electrodes are the “golden standard” catalysts. However, due to Pt cost, there is a need for cheaper alternatives. Indeed, highly active ruthenium nanoparticles are promising alternative. In this contribution, we use DFT (PBE-D2) calculations to understand the differences in the catalytic activities of Ru and Pt materials by considering slab models containing crystalline close packed planes, terraces, steps, islands and adatoms. Results reveal that the strong adsorption of isolated H atoms on either material and on various sites prevents the hydrogen evolution reaction from taking place. Regardless of the model considered, the formation of a monolayer is also too favorable, thus suggesting that higher coverages are needed before HER onset. The adsorption energies of H atoms exceeding the monolayer on platinum's crystalline surfaces, defective steps and terraces are very close to the ideal value, consistent with platinum's high catalytic activity. These results outline that the presence of lowly coordinated metal centers has little effect on the reactivity of Pt. The adsorption energy of extra H on Ru surfaces depends on the adsorption site: On non-defective sites, the adsorption of the extra H is unfavorable, leading to inefficient catalysts. In contrast, the adsorption on defective sites is favorable and close to the ideal value, thus suggesting an enhancement of the catalytic activity when Ru coordination decreases. These results outline that the reactivity toward hydrogen of Ru materials is more sensitive to surface morphology than Pt-based ones. Indeed, the presence of low coordinated centers is larger on Ru nanoparticles, thus rationalizing their high HER catalytic activity.

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Section: Defective M10 M7 and M1 Slabssupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Different role of ruthenium and platinum defective sites on the catalytic activity for the hydrogen evolution reaction

Fenoll,

Sodupe,

Solans Monfort

2024

Preprint

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“…For instance, PBE predict as conductors (E g = 0 eV) InAs and InSb despite their semiconducting character [152][153][154][155]. A viable way to attenuate this issue, reaching good accuracy, is the usage of hybrid functionals, such as B3LYP [156], PBE0 [157,158] and HSE06 [159,160] or to adopt the DFT + U framework [161][162][163][164][165][166][167][168][169][170][171].…”

Section: Application Of Computational Approaches To Predict Quantum S...mentioning

confidence: 99%

Impact of quantum size effects to the band gap of catalytic materials: a computational perspective*

Inico,

Saetta,

Di Liberto

2024

J. Phys.: Condens. Matter

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The evolution of nanotechnology has facilitated the development of catalytic materials with controllable composition and size, reaching the sub-nanometer limit. Nowadays, a viable strategy for tailoring and optimizing the catalytic activity involves controlling the size of the catalyst. This strategy is underpinned by the fact that the properties and reactivity of objects with dimensions on the order of nanometers can differ from those of the corresponding bulk material, due to the emergence of quantum size effects. Quantum size effects have a deep influence on the band gap of semiconducting catalytic materials. Computational studies are valuable for predicting and estimating the impact of quantum size effects. This perspective emphasizes the crucial role of modeling quantum size effects when simulating nanostructured catalytic materials. It provides a comprehensive overview of the fundamental principles governing the physics of quantum confinement in various experimentally observable nanostructures. Furthermore, this work may serve as a tutorial for modeling the electronic gap of simple nanostructures, highlighting that when working at the nanoscale, the finite dimensions of the material lead to an increase of the band gap because of the emergence of quantum confinement. This aspect is sometimes overlooked in computational chemistry studies focused on surfaces and nanostructures.

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“…On the basis of these results one can safely conclude that Pt 1– and Pt 4+ species, if present, are not involved in the HER, leaving only two species, Pt 0 and Pt 2+ , as the potential active sites, with Pt 2+ exhibiting a slightly better H adsorption free energy. Notice that a Δ G H = 0.22 eV results in a calculated 70-fold increase in activity with respect to Δ G H = −0.33 eV assuming a classical Volcano relation. , On this basis, the DFT results are consistent with the hypothesis of a combined role of O vacancies and Pt 2+ single-sites on the ceria support, although a minor role of Pt 0 single sites cannot be excluded. Thus, the superior HER catalytic performance of the Pt 1 /CeO x catalyst can be ascribed to the synergic effect of an O v -rich ceria where H 2 O is dissociated to intermediate H* species and an electron-poor site, Pt 2+ where H 2 is formed and desorbed, likely via a hydrogen spillover mechanism.…”

mentioning

confidence: 99%

Pt Single Atoms Supported on Defect Ceria as an Active and Stable Dual-Site Catalyst for Alkaline Hydrogen Evolution

Dao,

Di Liberto,

Yadav

et al. 2024

Nano Lett.

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This work evaluates the feasibility of alkaline hydrogen evolution reaction (HER) using Pt single-atoms (1.0 wt %) on defect-rich ceria (Pt1/CeO x ) as an active and stable dual-site catalyst. The catalyst displayed a low overpotential and a small Tafel slope in an alkaline medium. Moreover, Pt1/CeO x presented a high mass activity and excellent durability, competing with those of the commercial Pt/C (20 wt %). In this picture, the defective CeO x is active for water adsorption and dissociation to create H* intermediates, providing the first site where the reaction occurs. The H* intermediate species then migrate to adsorb and react on the Pt2+ isolated atoms, the site where H2 is formed and released. DFT calculations were also performed to obtain mechanistic insight on the Pt1/CeO x catalyst for the HER. The results indicate a new possibility to improve the state-of-the-art alkaline HER catalysts via a combined effect of the O vacancies on the ceria support and Pt2+ single atoms.

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Hydrogen complexes on single atom alloys: classical chemisorption versus coordination chemistry

Abstract: Single Atom Alloys (SAAs) represent one of the most promising class of heterogenous catalysts. They are based on isolated transition metal (TM) atoms stabilized in a host metal matrix. Among...

Cited by 6 publications

References 91 publications

Different role of ruthenium and platinum defective sites on the catalytic activity for the hydrogen evolution reaction

Different role of ruthenium and platinum defective sites on the catalytic activity for the hydrogen evolution reaction

Impact of quantum size effects to the band gap of catalytic materials: a computational perspective*

Pt Single Atoms Supported on Defect Ceria as an Active and Stable Dual-Site Catalyst for Alkaline Hydrogen Evolution

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