Abstract
AbstractFirst‐principles calculations of the electronic structure and charge‐trapping behavior of Σ3 {112} and Σ1 {110} twin boundaries (TBs) in anatase TiO2 are performed using an accurate hybrid density functional theory approach. The former is characterized experimentally using transmission electron microscopy (TEM) and very good agreement on the structure is found. The {110} twin has not yet been observed but TEM and scanning tuneling microscopy (STM) image simulations are presented to aid experimental identification. Holes are found to trap in a polaronic configuration at both the twin boundaries. The {112} TB presents more favorable sites for hole polaron formation at the boundary with trapping energies 0.16–0.18eV, more favorable than the bulk. The {110} TB presents hole polaron trapping sites ranging from 0.07 eV, less favorable, to 0.14 eV, more favorable, than the bulk. Neither boundary is found to favor electron trapping, indicating they are relatively benign to the performance of anatase as an n‐type conductor.
Highlights
The behavior of charge carriers in anatase TiO2 is of ut- aries (TBs) in anatase using accurate hybrid density functional most importance to its applications in energy generation as a theory (DFT) alongside simulated TEM and STM images to aid photocatalyst,[1,2,3] as an n-type transport layer in solar cells,[4,5,6] with comparison to experiment
Electrons or holes introduced formation energies and so are expected to occur frequently, a preby photoexcitation or charge injection can become trapped at diction supported by the experimental evidence of Σ3 {112} TBs point defects, extended defects. It is found as grain boundaries, dislocations, or surfaces), or in the perfect that both TBs alter hole polaron trapping energies—with more lattice where the charge carrier introduces a lattice polarization favorable traps at the Σ3 {112} TB and less favorable traps at the.[10,11,12,13,14,15]
We propose scanning probe microscopy on (001) oriented anatase (e.g., as grown on SrTiO3 (001)) could resolve this defect, and we provide simulated STM images to aid interpretation of experimental images
Summary
The behavior of charge carriers in anatase TiO2 is of ut- aries (TBs) in anatase using accurate hybrid density functional most importance to its applications in energy generation as a theory (DFT) alongside simulated TEM and STM images to aid photocatalyst,[1,2,3] as an n-type transport layer in solar cells,[4,5,6] with comparison to experiment Both TBs are found to have low and as a cathode in batteries.[7,8,9] Electrons or holes introduced formation energies and so are expected to occur frequently, a preby photoexcitation or charge injection can become trapped at diction supported by the experimental evidence of Σ3 {112} TBs point defects (vacancies or impurities), extended defects (such in hydrothermally coarsened samples of anatase.[21,22,23,24] It is found as grain boundaries, dislocations, or surfaces), or in the perfect that both TBs alter hole polaron trapping energies—with more lattice where the charge carrier introduces a lattice polarization favorable traps at the Σ3 {112} TB and less favorable traps at the (polaronic self-trapping).[10,11,12,13,14,15] The formation of small polarons Σ1 {110}—but neither provides sites for electron trapping nor are in TiO2 can affect the adsorption and reaction of molecules at new states introduced in the band gap. Hole traps at interfaces in the bulk could pose problems for photocatalysis as it could prevent charge
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