Review of First-Principles Studies of TiO2: Nanocluster, Bulk, and Material Interface

Effects of La-N Co-Doping of BaTiO3 on Its Electron-Optical Properties for Photocatalysis: A DFT Study

In cation-anion co-doping, rare earth elements excel at regulating the electronic structure of perovskites, leading to their improved photocatalytic performance. In this regard, the impact of co-doping rare earth elements at the Ba and Ti sites in BaTiO3 on its electronic and photocatalytic properties was thoroughly investigated based on 2 × 2 × 2 supercell structures of BaTiO3 with different La concentrations of 12.5% and 25% using DFT calculations. The band structure, density of states, charge density difference, optical properties, and the redox band edge of the co-doped models mentioned above were analyzed. The results indicated that the BaTiO3 structure co-doped with 25% La at the Ti site exhibited higher absorption in the visible range and displayed a remarkable photocatalytic water-splitting performance. The introduced La dopant at the Ti site effectively reduced the energy required for electronic transitions by introducing intermediate energy levels within the bandgap. Our calculations and findings of this study provide theoretical support and reliable predictions for the exploration of BaTiO3 perovskites with superior photocatalytic performances.

Density functional theory for doped TiO2: current research strategies and advancements

Since the inception of the density functional theory (DFT) by Hohenberg and Kohn in 1964, it rapidly became an indispensable theoretical tool across various disciplines, such as chemistry, biology, and materials science, among others. This theory has ushered in a new era of computational research, paving the way for substantial advancements in fundamental understanding. Today, DFT is routinely employed for a diverse range of applications, such as probing new material properties and providing a profound understanding of the mechanisms underlying physical, chemical, and biological processes. Even after decades of active utilization, the improvement of DFT principles has never been slowed down, meaning that more accurate theoretical results are continuously generated with time. This work highlights the latest achievements acquired by DFT in the specific research field, namely the theoretical investigations of doped TiO2systems, which have not been comprehensively reviewed and summarized yet. Successful progress in this niche is currently hard to imagine without the support by DFT. It can accurately reveal new TiO2properties after introducing the desired dopant and help to find the optimal system design for a specific application prior to proceeding to more time-consuming and expensive experimental research. Hence, by evaluating a selection of the most recent research studies, we aim to highlight the pertinent aspects of DFT as they relate to the study of doped TiO2systems. We also aim to shed light on the strengths and weaknesses of DFT and present the primary strategies employed thus far to predict the properties of various doped TiO2systems reliably.

Estimating Nonradiative Excited-State Lifetimes in Photoactive Semiconducting Nanostructures

The time evolution of the exciton generated by light adsorption in a photocatalyst is an important feature that can be approached from full nonadiabatic molecular dynamics simulations. Here, a crucial parameter is the nonradiative recombination rate between the hole and the electron that form the exciton. In the present work, we explore the performance of a Fermi's golden rule-based approach on predicting the recombination rate in a set of photoactive titania nanostructures, relying solely on the coupling of the ground and first excited state. In this scheme the analysis of the first excited state is carried out by invoking Kasha's rule thus avoiding computationally expensive nonadiabatic molecular dynamics simulations and resulting in an affordable estimate of the recombination rate. Our results show that, compared to previous ones from nonadiabatic molecular dynamics simulations, semiquantitative recombination rates can be predicted for the smaller titania nanostructures, and qualitative values are obtained from the larger ones. The present scheme is expected to be useful in the field of computational heterogeneous photocatalysis whenever a complex and computationally expensive full nonadiabatic molecular dynamics cannot be carried out.

Electronic Bulk and Surface Properties of Titanium Dioxide Studied by DFT-1/2

Transparent conductive oxides, such as TiO2, are important functional materials for optoelectronic and photovoltaic devices. We investigate the electronic bulk properties of the TiO2 phases rutile and anatase with the DFT-1/2 method and obtain a quantitatively good description of their electronic band structures. We then applied this method to the (001) surfaces of rutile and anatase and calculated their ionization potentials (IPs) and work functions (WF). To relate these calculated surface properties with values from experiments, we evaluated the effect of varying the oxygen stoichiometry at the surface on both IP and WF.

Electronic structure and optical properties of Br- and Cl-doped rutile TiO2 for application in self-cleaning and photovoltaic panel's coatings: first-principle calculations

Development of novel self-cleaning technologies, especially those based on semiconductor photocatalysis system, is one of the most important research problems in environmental cleanup. Titanium dioxide (TiO₂) is a well-known semiconductor photocatalyst that has a strong photocatalytic activity in the ultra-violet part of the spectrum while its photocatalytic efficiency is very limited within the visible range due to its large band gap. In the field of photocatalytic materials, doping is an efficient method to increase the spectral response and promote charge separation. However, the type of dopant is not the only important factor, but also its position in the material lattice. In the present study, we have carried out first-principle calculations based on density functional theory to explore how particular doping configuration, such as Br or Cl doping at an O site, may influence the electronic structure and the charge density distribution within rutile TiO₂. Furthermore, optical properties such as the absorption coefficient, the transmittance, and reflectance spectra have also been derived from the calculated complex dielectric function and examined to see whether this doping configuration has any effect on the use of the material as a self-cleaning coating on photovoltaic panels.

Insight into the Effect of Anionic–Anionic Co-Doping on BaTiO3 for Visible Light Photocatalytic Water Splitting: A First-Principles Hybrid Computational Study

In this research, we thoroughly studied the electronic properties and optical absorption characteristics with double-hole coupling of anions–anion combinations for designing effective photocatalysts for water redox using first-principles methods within the hybrid Heyd–Scuseria–Ernzerhof (HSE06) exchange–correlation formalisms. The findings reveal that the values of formation energy of both the anion mono- and co-doped configurations increase monotonically as the chemical potential of oxygen decreases. The N–N co-doped BaTiO3 exhibits a more favorable formation energy under an O-poor condition compared with other configurations, indicating that N and N pairs are more likely to be synthesized successfully. Interestingly, all the co-doping configurations give a band gap reduction with suitable position for oxygen production and hydrogen evolution. The obtained results demonstrate that all the co-doped systems constitute a promising candidate for photocatalytic water-splitting reactions. Furthermore, the enhanced ability of the anionic-anionic co-doped BaTiO3 to absorb visible light and the positions of band edges that closely match the oxidation-reduction potentials of water suggest that these configurations are viable photocatalysts for visible-light water splitting. Therefore, the wide-band gap semiconductor band structures can be tuned by double-hole doping through anionic combinations, and high-efficiency catalysts for water splitting using solar energy can be created as a result.

Tuning the electronic structure of BaTiO3 for an enhanced photocatalytic performance using cation–anion codoping: a first-principles study

(Mo + C)-, (W + C)-, (Mo + 2N)- and (W + 2N)-codoped BaTiO₃ are predicted to be promising photocatalysts for water splitting under visible-light-irradiation.