Scenarios of polaron-involved molecular adsorption on reduced TiO2(110) surfaces

Cao, Yunjun; Yu, Min; Qi, Shandong; Huang, Shiming; Wang, Tingting; Xu, Mingchun; Hu, Shujun; Shen, Yan

doi:10.1038/s41598-017-06557-6

Cited by 19 publications

(35 citation statements)

References 55 publications

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“…[1][2][3] However, considerably less is known about the other side of this interplay between adsorbates and defects, namely how adsorbates alter the distribution of defects at the surfaces of materials. 4,5 This is the issue we address in the current study through a detailed set of experiments and simulations of water on rutile TiO2, in which we focus on the interplay between water and excess electron defects.…”

Section: Table Of Contents (Toc) Graphicmentioning

confidence: 99%

Visualization of Water-Induced Surface Segregation of Polarons on Rutile TiO₂(110)

Yim

Chen

Shaw

et al. 2018

J. Phys. Chem. Lett.

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Water-oxide surfaces are ubiquitous in nature and of widespread importance to phenomena like corrosion as well as contemporary industrial challenges such as energy production through water splitting. So far, a reasonably robust understanding of the structure of such interfaces under certain conditions has been obtained. Considerably less is known about how overlayer water modifies the inherent reactivity of oxide surfaces. Here we address this issue experimentally for rutile TiO(110) using scanning tunneling microscopy and photoemission, with complementary density functional theory calculations. Through detailed studies of adsorbed water nanoclusters and continuous water overlayers, we determine that excess electrons in TiO are attracted to the top surface layer by water molecules. Measurements on methanol show similar behavior. Our results suggest that adsorbate-induced surface segregation of polarons could be a general phenomenon for technologically relevant oxide materials, with consequences for surface chemistry and the associated catalytic activity.

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Section: Table Of Contents (Toc) Graphicmentioning

confidence: 99%

Visualization of Water-Induced Surface Segregation of Polarons on Rutile TiO₂(110)

Yim

Chen

Shaw

et al. 2018

J. Phys. Chem. Lett.

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“…Simultaneously, reactant binding energy and efficiency of reactant dissociation can be enhanced. 10 , 27 − 30 Density functional theory (DFT) calculations conducted by the Liu group reported that EPs induced by titanium interstitials or single hydrogen atom preferred to reside in deeper inner layers when the surface was clean, while they tended to diffuse toward surface sites in the presence of adsorbed water or methanol. 9 , 30 The polaron–adsorbate interaction drove partial dissociations of the adsorbates on the reduced TiO 2 (110) surface.…”

Section: Introductionmentioning

confidence: 99%

“…Likewise, by combining IR spectroscopy and DFT calculations, Cao et al suggested transformation of sublayer polarons into surface polarons, induced by adsorption of CO and NO molecules. 27 A combined experimental/theoretical study of CO adsorbed on Ti-containing materials showed a complex photochemistry involving plasmons and polaronic effects. 31 …”

Section: Introductionmentioning

confidence: 99%

CO Adsorbate Promotes Polaron Photoactivity on the Reduced Rutile TiO₂(110) Surface

Cheng

Zhu

Fang

et al. 2021

JACS Au

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Polarons play a major role in determining the chemical properties of transition-metal oxides. Recent experiments show that adsorbates can attract inner polarons to surface sites. These findings require an atomistic understanding of the adsorbate influence on polaron dynamics and lifetime. We consider reduced rutile TiO 2 (110) with an oxygen vacancy as a prototypical surface and a CO molecule as a classic probe and perform ab initio adiabatic molecular dynamics, time-domain density functional theory, and nonadiabatic molecular dynamics simulations. The simulations show that subsurface polarons have little influence on CO adsorption and CO can desorb easily. On the contrary, surface polarons strongly enhance CO adsorption. At the same time, the adsorbed CO attracts polarons to the surface, allowing them to participate in catalytic processes with CO. The CO interaction with polarons changes their orbital origin, suppresses polaron hopping, and stabilizes them at surface sites. Partial delocalization of polarons onto CO decouples them from free holes, decreasing the nonadiabatic coupling and shortening the quantum coherence time, thereby reducing charge recombination. The calculations demonstrate that CO prefers to adsorb at the next-nearest-neighbor five-coordinated Ti 3+ surface electron polaron sites. The reported results provide a fundamental understanding of the influence of electron polarons on the initial stage of reactant adsorption and the effect of the adsorbate–polaron interaction on the polaron dynamics and lifetime. The study demonstrates how charge and polaron properties can be controlled by adsorbed species, allowing one to design high-performance transition-metal oxide catalysts.

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“…[21][22][23] Excess electrons are found to orig-inate mostly from surface defects, such as oxygen vacancies, Nb impurities, hydroxyl groups and interstitial titanium atoms. [23][24][25][26] Formation of polarons is particularly favorable at Ti 4+ sites in the near-surface region, 27 with consequent effects on the adsorption 28 and on the stability of the surface. At high reduction states, the strong polaronic repulsion was found to drive the surface from a (1×1) termination to a (1×2) reconstruction.…”

Section: Introductionmentioning

confidence: 99%

Formation and dynamics of small polarons on the rutile TiO2 (110) surface

et al. 2018

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Charge trapping and formation of polarons is a pervasive phenomenon in transition metal oxide compounds, in particular at the surface, affecting fundamental physical properties and functionalities of the hosting materials. Here we investigate via first-principle techniques the formation and dynamics of small polarons on the reduced surface of titanium dioxide, an archetypal system for polarons, for a wide range of oxygen vacancy concentrations. We report how the essential features of polarons can be adequately accounted in terms of few quantities: the local structural and chemical environment, the attractive interaction between negatively charged polarons and positively charged oxygen vacancies, and the spin-dependent polaron-polaron Coulomb repulsion. We combined molecular dynamics simulations on realistic samples derived from experimental observations with simplified static models, aiming to disentangle the various variables at play. We find that depending on the specific trapping site, different types of polarons can be formed, with distinct orbital symmetries and different degree of localization and structural distortion. The energetically most stable polaron site is the subsurface Ti atom below the undercoordinated surface Ti atom, owing to a small energy cost to distort the lattice and a suitable electrostatic potential. Polaron-polaron repulsion and polaron-vacancy attraction determine the spatial distribution of polarons as well as the energy of the polaronic in-gap state. In the range of experimentally reachable oxygen vacancy concentrations the calculated data are in excellent agreement with observations, thus validating the overall interpretation.arXiv:1805.01849v1 [cond-mat.mtrl-sci]

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Scenarios of polaron-involved molecular adsorption on reduced TiO2(110) surfaces

Cited by 19 publications

References 55 publications

Visualization of Water-Induced Surface Segregation of Polarons on Rutile TiO₂(110)

Visualization of Water-Induced Surface Segregation of Polarons on Rutile TiO₂(110)

CO Adsorbate Promotes Polaron Photoactivity on the Reduced Rutile TiO₂(110) Surface

Formation and dynamics of small polarons on the rutile TiO2 (110) surface

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Scenarios of polaron-involved molecular adsorption on reduced TiO2(110) surfaces

Cited by 19 publications

References 55 publications

Visualization of Water-Induced Surface Segregation of Polarons on Rutile TiO2(110)

Visualization of Water-Induced Surface Segregation of Polarons on Rutile TiO2(110)

CO Adsorbate Promotes Polaron Photoactivity on the Reduced Rutile TiO2(110) Surface

Formation and dynamics of small polarons on the rutile TiO2 (110) surface

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Visualization of Water-Induced Surface Segregation of Polarons on Rutile TiO₂(110)

Visualization of Water-Induced Surface Segregation of Polarons on Rutile TiO₂(110)

CO Adsorbate Promotes Polaron Photoactivity on the Reduced Rutile TiO₂(110) Surface