Tuning electronic levels in photoactive hydroxylated titania nanosystems: combining the ligand dipole effect and quantum confinement

Recio-Poo, Miguel; Morales-García, Ángel; Illas, Francesc; Bromley, Stefan T.

doi:10.1039/d3nr06189b

Cited by 3 publications

(3 citation statements)

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“…A typical case is the mixed rutile and anatase TiO 2 phase, where experimental measurements and theoretical calculations have yielded several interpretations of the band alignment and charge transfer mechanisms. , These discrepancies can be attributed to both intrinsic factors, such as surface orientations, and extrinsic factors, such as environmental conditions, which collectively affect the absolute band edges and their alignment. A recent theoretical study further showed that the absolute energy levels in TiO 2 nanoparticles can be modified intrinsically by size and extrinsically by hydroxylation upon interaction with aqueous environments . Finally, in photocatalytic water splitting, the positions of the band edges of metal oxide catalysts are expected to evolve relative to the redox potentials of water due to the variation of surface species.…”

Section: Resultsmentioning

confidence: 99%

“…A recent theoretical study further showed that the absolute energy levels in TiO 2 nanoparticles can be modified intrinsically by size and extrinsically by hydroxylation upon interaction with aqueous environments. 89 Finally, in photocatalytic water splitting, the positions of the band edges of metal oxide catalysts are expected to evolve relative to the redox potentials of water due to the variation of surface species. Our theoretical findings highlight further the importance of in situ characterization techniques for capturing the electronic structure of photocatalysts in operating conditions.…”

Section: Resultsmentioning

confidence: 99%

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Environment-Driven Variability in Absolute Band Edge Positions and Work Functions of Reduced Ceria

Zhang,

Blackman,

Palgrave

et al. 2024

J. Am. Chem. Soc.

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The absolute band edge positions and work function (Φ) are the key electronic properties of metal oxides that determine their performance in electronic devices and photocatalysis. However, experimental measurements of these properties often show notable variations, and the mechanisms underlying these discrepancies remain inadequately understood. In this work, we focus on ceria (CeO 2 ), a material renowned for its outstanding oxygen storage capacity, and combine theoretical and experimental techniques to demonstrate environmental modifications of its ionization potential (IP) and Φ. Under O-deficient conditions, reduced ceria exhibits a decreased IP and Φ with significant sensitivity to defect distributions. In contrast, the IP and Φ are elevated in O-rich conditions due to the formation of surface peroxide species. Surface adsorbates and impurities can further augment these variabilities under realistic conditions. We rationalize the shifts in energy levels by separating the individual contributions from bulk and surface factors, using hybrid quantum mechanical/molecular mechanical (QM/MM) embedded-cluster and periodic density functional theory (DFT) calculations supported by interatomic-potential-based electrostatic analyses. Our results highlight the critical role of on-site electrostatic potentials in determining the absolute energy levels in metal oxides, implying a dynamic evolution of band edges under catalytic conditions.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Environment-Driven Variability in Absolute Band Edge Positions and Work Functions of Reduced Ceria

Zhang,

Blackman,

Palgrave

et al. 2024

J. Am. Chem. Soc.

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“…Reciprocal space sampling at Γ point only was found to be sufficiently accurate. 17 A 20 Å vacuum space between repeated slabs in the direction perpendicular to the surface was used avoid the artificial interslab interactions.…”

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confidence: 99%

Size-Dependent Ab Initio Atomistic Thermodynamics from Cluster to Bulk: Application to Hydration of Titania Nanoparticles

Recio-Poo,

Morales-García,

Illas

et al. 2024

J. Phys. Chem. Lett.

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Ab initio atomistic thermodynamics (AIAT) has become an indispensable tool to estimate Gibbs free energy changes for solid surfaces interacting with gaseous species relative to pressure ( p ) and temperature ( T ). For such systems, AIAT assumes that solid vibrational contributions to Gibbs free energy differences cancel out. However, the validity of this assumption is unclear for nanoscale systems. Using hydrated titania nanoparticles (NPs) as an example, we estimate the vibrational contributions to the Gibbs free energy of hydration (Δ G hyd ( T , p )) for arbitrary NP size and degree of hydration. Comparing Δ G hyd ( T , p ) phase diagrams for NPs when considering these contributions (AIAT nano ) relative to a standard AIAT approach reveals significant qualitative and quantitative differences, which only become negligible for large systems. By constructing a size-dependent Δ G hyd ( T , p ) phase diagram, we illustrate how our approach can provide deeper insights into how nanosytems interact with their environments, with many potential applications (e.g., catalytic nanoparticles, biological colloids, nanoparticulate pollutants).

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Anatase TiO₂ Surface Hydration: Infrared Vibrational Assignment and Facet-Specific Stability

Luo,

Hood,

Martinson

et al. 2024

J. Phys. Chem. C

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Anatase TiO 2 nanoparticles support a subtle diversity of surface aqua and hydroxy coordination environments that are characteristic of distinct facets and defect sites. The disparate properties and stability of each molecularly or dissociatively absorbed water environment may provide unique reactivity for facetand site-selective atomic layer deposition (ALD). We probe the temperaturedependent and facet-specific stretching frequency and stability of surface hydroxyls on faceted anatase TiO 2 nanoparticles via in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Well-defined truncated octahedra, disks, and rods fabricated through hydrothermal synthesis present dominant ( 101), (001), and (010) facets, respectively. The selective dehydration of discrete local coordination environments as a function of temperature provides a potential pathway to siteselective and facet-selective ALD on metal oxide nanomaterials.

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Tuning electronic levels in photoactive hydroxylated titania nanosystems: combining the ligand dipole effect and quantum confinement

Abstract: Reducing the size of titania (TiO2) to the nanoscale promotes the photoactive anatase phase for use in a range of applications from industrial catalysis to environment remediation. The nanoscale dimensions...

Cited by 3 publications

References 53 publications

Environment-Driven Variability in Absolute Band Edge Positions and Work Functions of Reduced Ceria

Environment-Driven Variability in Absolute Band Edge Positions and Work Functions of Reduced Ceria

Size-Dependent Ab Initio Atomistic Thermodynamics from Cluster to Bulk: Application to Hydration of Titania Nanoparticles

Anatase TiO₂ Surface Hydration: Infrared Vibrational Assignment and Facet-Specific Stability

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Tuning electronic levels in photoactive hydroxylated titania nanosystems: combining the ligand dipole effect and quantum confinement

Abstract: Reducing the size of titania (TiO2) to the nanoscale promotes the photoactive anatase phase for use in a range of applications from industrial catalysis to environment remediation. The nanoscale dimensions...

Cited by 3 publications

References 53 publications

Environment-Driven Variability in Absolute Band Edge Positions and Work Functions of Reduced Ceria

Environment-Driven Variability in Absolute Band Edge Positions and Work Functions of Reduced Ceria

Size-Dependent Ab Initio Atomistic Thermodynamics from Cluster to Bulk: Application to Hydration of Titania Nanoparticles

Anatase TiO2 Surface Hydration: Infrared Vibrational Assignment and Facet-Specific Stability

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Anatase TiO₂ Surface Hydration: Infrared Vibrational Assignment and Facet-Specific Stability