Polarization Effects on the Surface Chemistry of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>PbTiO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>-Supported Pt Films

Kolpak, Alexie M.; Grinberg, Ilya; Rappe, Andrew M.

doi:10.1103/physrevlett.98.166101

Cited by 95 publications

(100 citation statements)

References 28 publications

(28 reference statements)

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“…1). As usual, below STO three Pt(001) layers are included to screen the dipole moments of STO [24,25]. We use a (2 × 1) surface cell, with a 2 × 4 × 1 mesh to sample k space.…”

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confidence: 99%

TiO2 /Ferroelectric Heterostructures as Dynamic Polarization-Promoted Catalysts for Photochemical and Electrochemical Oxidation of Water

Lee

Selloni

2014

Phys. Rev. Lett.

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Using first-principles density functional theory calculations, we explore the chemical activity of epitaxial heterostructures of TiO 2 anatase on strained polar SrTiO 3 films focusing on the oxygen evolution reaction (OER), the bottleneck of water splitting. Our results show that the reactivity of the TiO 2 surface is tuned by electric dipoles dynamically induced by the adsorbed species during the intermediate steps of the reaction while the initial and final steps remain unaffected. Compared to the OER on unsupported TiO 2 , the combined effects of the dynamically induced dipoles and epitaxial strain strongly reduce rate-limiting thermodynamic barriers and significantly improve the efficiency of the reaction. DOI: 10.1103/PhysRevLett.112.196102 PACS numbers: 82.45.Jn, 82.45.Un, 82.50.−m, 77.55.fp Titanium dioxide (TiO 2 ) is widely used in photocatalysis and solar energy conversion due to its many favorable properties, like stability against photocorrosion and proper band alignment relative to the water redox potentials [1][2][3]. However, the efficiency of TiO 2 is notoriously low, and efforts at improving it through modifications such as doping [4] or synthesis of (nano)crystals exposing highly reactive facets [5] have encountered only limited success. Among the possible alternatives to TiO 2 , polar materials have recently attracted significant interest because their surface dipoles can react easily with charged species and supply built-in electric potentials to increase the carrier mobility [6,7]. However, control of the surface reactivity of these materials is difficult [8], e.g., because exposed surface dipoles often cause undesired atomic or electronic reconstructions and unexpected adsorption of charged species which can interfere with the reaction of interest [9][10][11]. Less well known than TiO 2 and polar semiconductors are heterostructures composed of stable TiO 2 thin films supported by a ferroelectric substrate [12,13]. Experimental studies have shown that the surface reactivity of TiO 2 is directly influenced and improved by the underlying ferroelectric domain structure, an effect that has been attributed to the combined efficient absorption and charge separation in the ferroelectric substrate and transport across the TiO 2 =substrate interface [12,13]. Despite some encouraging results [13,14], however, the interest in such TiO 2 =ferroeletric heterostructures has remained limited. In particular, their physical properties are largely unexplored and an atomic-scale understanding of their reactivity is missing.We present here a first-principles density functional theory (DFT) study of TiO 2 =ferroelectric heterostructures, which provides evidence that these composite materials can have a substantially enhanced reactivity relative to TiO 2 . We focus on model heterostructures composed of a TiO 2 (001) film of anatase (the TiO 2 polymorph most efficient for photocatalysis [15]) supported by a nearly ferroelectric SrTiO 3 (STO) substrate that can easily acquire a macroscopic polarization in the p...

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“…1). As usual, below STO three Pt(001) layers are included to screen the dipole moments of STO [24,25]. We use a (2 × 1) surface cell, with a 2 × 4 × 1 mesh to sample k space.…”

mentioning

confidence: 99%

TiO2 /Ferroelectric Heterostructures as Dynamic Polarization-Promoted Catalysts for Photochemical and Electrochemical Oxidation of Water

Lee

Selloni

2014

Phys. Rev. Lett.

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“…The ability to electrically switch the reactivity of a surface could form the basis for new classes of thin-film chemical actuators [23,24] and catalysts [25], offering dynamical control of reactivity and selectivity over a wide range in a single system. Further understanding of the interactions of ambients with polarization at ferroelectric surfaces promises to provide a new means for manipulating both ferroelectricity and surface chemistry.…”

Section: -3mentioning

confidence: 99%

“…Experiments have shown that ferroelectric surfaces with opposite polarity have different properties for adsorbing molecules [23,24]. Ab initio calculations have found that catalytic activity [25] and equilibrium surface stoichiometry [26] depend upon polarization orientation. In this work, we demonstrate the converse effect-that the chemical environment can control the polarization of a ferroelectric film by determining the ionic compensation at its surface.…”

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confidence: 99%

Switching a ferroelectric film by asphyxiation

Hlinka¹

2009

Physics

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According to recent experiments and predictions, the orientation of the polarization at the surface of a ferroelectric material can affect its surface chemistry. Here we demonstrate the converse effect: the chemical environment can control the polarization orientation in a ferroelectric film. In situ synchrotron x-ray scattering measurements show that high or low oxygen partial pressure induces outward or inward polarization, respectively, in an ultrathin PbTiO 3 film. Ab initio calculations provide insight into surface structure changes observed during chemical switching. DOI: 10.1103/PhysRevLett.102.047601 PACS numbers: 77.80.Fm, 68.43.Àh, 68.47.Gh, 77.84.Dy Ferroelectric materials are fascinating and useful because the spontaneous polarization which appears below the Curie temperature T C is strongly coupled to long-range electric and stress fields, leading to outstanding properties such as piezoelectricity and electrically switchable structure [1,2]. Understanding the behavior of ultrathin ferroelectric films, for which interfacial effects begin to dominate over the physics of the film interior, has been an area of major progress recently [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. One of the most important interfacial effects is the screening of the intrinsic surface charge of the polar phase [19], since this bound charge produces an electric field opposing the bulk polarization. The energy of this depolarizing field can be reduced by stripe domain formation [3][4][5][6][7][8][9][10] or by compensation via free charge at the interfaces [8,[11][12][13][14][15][16][17]. In both cases, incomplete screening leads to a depression of T C for thinner films and a critical thickness below which the polar phase is not stable. While electronic charge in metallic electrodes provides screening adequate to stabilize the polar phase down to nanometer dimensions [8,11,12,17], similar small critical thicknesses have been observed for films without surface electrodes [2,13,15,16]. Ab initio calculations [15,16] have indicated that extra ions or point defects could be providing charge compensation at these surfaces. Such ionic compensation of ferroelectric surfaces has also been inferred from electric force microscopy measurements [20]. The electronic or ionic nature of the compensating charge at interfaces has become a subject of debate for polar oxides in general [19,21,22].Because of this evidence that ions can provide surface charge compensation for ferroelectrics, potentially giving new device functionality, several recent studies have focused on the interaction between the chemistry of the environment and the polarization orientation. Experiments have shown that ferroelectric surfaces with opposite polarity have different properties for adsorbing molecules [23,24]. Ab initio calculations have found that catalytic activity [25] and equilibrium surface stoichiometry [26] depend upon polarization orientation. In this work, we demonstrate the converse effect-that the chemical environment can control the p...

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“…[20][21][22][23] Theoretical studies have suggested that ultrathin transition metal layers on ferroelectric surfaces can display unique catalytic properties. For example, it has been suggested that CO can dissociate on Pt on negatively poled PbTiO 3 , 24 chemistry that is not observed on any known form of Pt. While early experiments suggested that ferroelectric polarization can influence CO oxidation rates on transition metals, 25 more recent experiments revealed no effect of the substrate polarization on the interaction of CO with transition metals.…”

Section: Introductionmentioning

confidence: 99%

Growth, structure, and electronic properties of nonpolar thin films on a polar substrate:Cr2O3on ZnO (0001) and ZnO (0001¯
Zhu
¹
,
Morales-Acosta
²
,
Shen
³

et al. 2015
Phys. Rev. B
10
0
3
0
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The growth and geometric and electronic structures of Cr 2 O 3 layers on the polar ZnO surfaces were characterized to determine how polar substrates can influence the properties of non-polar films. Photoelectron spectroscopy (XPS and UPS), high resolution transmission electron microscopy (HRTEM), electron diffraction (RHEED and LEED), and x-ray diffraction and reflectivity (XRD and XRR) were employed to characterize the growth mode, film quality and interfacial electronic properties. Chromium oxide growth on ZnO 0001 and 0001 followed the same trends: two dimensional growth with initial disorder followed by the formation of epitaxial Cr 2 O 3 0001 . Despite the initial disorder, HRTEM and XRD/XRR measurements on thicker films revealed an abrupt interface with the Cr 2 O 3 lattice extending all the way to the interface. This indicates that above a critical thickness of 10 -15 Cr-O 3 -Cr repeat units the entire film reorganizes into an ordered structure. It is postulated that the oxygen remained ordered throughout the growth but that the chromium initially filled interstices randomly in the oxygen sublattice which allowed the film to eventually grow with a well-defined epitaxial relationship with the substrate. The polar interfaces showed a small band offset that decayed with increasing film thickness, suggesting that the compensating charges at the interface 2 may partially migrate to the film surface. No evidence of formal changes in the Cr oxidation state at the interfaces was seen. On the other hand, statistical analyses of UPS valence band spectra revealed an enhanced density of states near the valence band edge for Cr 2 O 3 on ZnO 0001 , consistent with stabilization of the positive interface by filling surface electronic states.In contrast, no significant valence band differences were observed between bulk Cr 2 O 3 and thin Cr 2 O 3 layers on ZnO 0001 suggesting a different charge compensation mechanism on the negative surface. The potential impact of these findings on the surface properties of chromium oxide thin films is discussed. PACS number(s): 68.47.Gh,

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Polarization Effects on the Surface Chemistry ofPbTiO3-Supported Pt Films

Cited by 95 publications

References 28 publications

TiO2 /Ferroelectric Heterostructures as Dynamic Polarization-Promoted Catalysts for Photochemical and Electrochemical Oxidation of Water

TiO2 /Ferroelectric Heterostructures as Dynamic Polarization-Promoted Catalysts for Photochemical and Electrochemical Oxidation of Water

Switching a ferroelectric film by asphyxiation

Growth, structure, and electronic properties of nonpolar thin films on a polar substrate:Cr2O3on ZnO (0001) and ZnO (0001¯
Zhu
¹
,
Morales-Acosta
²
,
Shen
³

et al. 2015
Phys. Rev. B
10
0
3
0
View full text Add to dashboard Cite

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Polarization Effects on the Surface Chemistry ofPbTiO3-Supported Pt Films

Cited by 95 publications

References 28 publications

TiO2 /Ferroelectric Heterostructures as Dynamic Polarization-Promoted Catalysts for Photochemical and Electrochemical Oxidation of Water

TiO2 /Ferroelectric Heterostructures as Dynamic Polarization-Promoted Catalysts for Photochemical and Electrochemical Oxidation of Water

Switching a ferroelectric film by asphyxiation

Growth, structure, and electronic properties of nonpolar thin films on a polar substrate:Cr2O3on ZnO (0001) and ZnO (0001¯Zhu1, Morales-Acosta2, Shen3 et al. 2015Phys. Rev. B10030View full textAdd to dashboardCite

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Growth, structure, and electronic properties of nonpolar thin films on a polar substrate:Cr2O3on ZnO (0001) and ZnO (0001¯
Zhu
¹
,
Morales-Acosta
²
,
Shen
³

et al. 2015
Phys. Rev. B
10
0
3
0
View full text Add to dashboard Cite