scholarly journals Formation of OH Groups and Hydrogen Peroxide Molecules on the Tio2 Anatase Surface: Pseudopotential Calculations

2018 ◽  
Vol 3 (1) ◽  
pp. 46-52
Author(s):  
V.G. Zavodinsky ◽  
K.S. Makarevich ◽  
S.V. Pyachin
Keyword(s):  
Hydrogen Peroxide ◽  
Titanium Dioxide ◽  
Organic Pollutants ◽  
Density Functional ◽  
Formation Energy ◽  
Desorption Energy ◽  
Oh Groups ◽  
Tio2 Anatase ◽  
Pseudopotential Calculations ◽  
Sun Light

The density functional pseudopotential simulation was carried out to study dissociation of the H2O molecule on the TiO2 anatase surface (pure and W doped). Formation and desorption of the OH groups were studied, and it was shown that the adding of tungsten into titanium dioxide leads to reduction of the desorption energy of OH groups from 6.06 eV to 4.74 eV. Creation of the hydrogen peroxide H2O2 molecules was also investigated. Substitution of Ti with W on the TiO2 anatase surface decreases the formation energy of hydrogen peroxide molecules and moves it up to the range of visible sun light. Decrease of the formation energy of free OH groups and H2O2 molecules, which are fissile oxidizers, increases their quantity in water and promotes increase in effectiveness of organic pollutants decomposition.

scholarly journals Tuning the optoelectronic properties of hematite with rhodium doping for photoelectrochemical water splitting using density functional theory approach

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Abdur Rauf ◽  
Muhammad Adil ◽  
Shabeer Ahmad Mian ◽  
Gul Rahman ◽  
Ejaz Ahmed ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
Optical Absorption ◽  
Water Splitting ◽  
Density Functional ◽  
Formation Energy ◽  
Visible Region ◽  
Photoelectrochemical Water Splitting ◽  
Theory Approach ◽  
Functional Theory

AbstractHematite (Fe2O3) is one of the best candidates for photoelectrochemical water splitting due to its abundance and suitable bandgap. However, its efficiency is mostly impeded due to the intrinsically low conductivity and poor light absorption. In this study, we targeted this intrinsic behavior to investigate the thermodynamic stability, photoconductivity and optical properties of rhodium doped hematite using density functional theory. The calculated formation energy of pristine and rhodium doped hematite was − 4.47 eV and − 5.34 eV respectively, suggesting that the doped material is thermodynamically more stable. The DFT results established that the bandgap of doped hematite narrowed down to the lower edge (1.61 eV) in the visible region which enhanced the optical absorption and photoconductivity of the material. Moreover, doped hematite has the ability to absorb a broad spectrum (250–800) nm. The enhanced optical absorption boosted the photocurrent and incident photon to current efficiency. The calculated results also showed that the incorporation of rhodium in hematite induced a redshift in optical properties.

scholarly journals On the Effects of Doping on the Catalytic Performance of (La,Sr)CoO3. A DFT Study of CO Oxidation

Catalysts ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 312 ◽  
Author(s):  
Antonella Glisenti ◽  
Andrea Vittadini
Keyword(s):  
Catalytic Activity ◽  
Co Oxidation ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Formation Energy ◽  
Oxygen Vacancies ◽  
Catalytic Performance ◽  
Energy Profiles ◽  
High Concentrations ◽  
3D Impurities

The effects of modifying the composition of LaCoO3 on the catalytic activity are predicted by density functional calculations. Partially replacing La by Sr ions has benefical effects, causing a lowering of the formation energy of O vacancies. In contrast to that, doping at the Co site is less effective, as only 3d impurities heavier than Co are able to stabilize vacancies at high concentrations. The comparison of the energy profiles for CO oxidation of undoped and of Ni-, Cu-m and Zn-doped (La,Sr)CoO3(100) surface shows that Cu is most effective. However, the effects are less spectacular than in the SrTiO3 case, due to the different energetics for the formation of oxygen vacancies in the two hosts.

scholarly journals The Use of Sodium Carbonate—Hydrogen Peroxide (2/3) in the Modified Fenton Reaction to Degradation PAHs in Coke Wastewater

Proceedings ◽  
2019 ◽  
Vol 16 (1) ◽  
pp. 44
Author(s):  
Kozak ◽  
Włodarczyk-Makuła
Keyword(s):  
Hydrogen Peroxide ◽  
Organic Pollutants ◽  
Sodium Carbonate ◽  
Uv Light ◽  
Oxygen Demand ◽  
Organic Matrix ◽  
Coke Wastewater ◽  
Polycyclic Aromatic ◽  
Pahs Concentration ◽  
Modified Fenton

The aim of the research was to determine the effectiveness of removing micro-organic pollutants, including PAHs, using the modified Fenton method. The tested material was pretreated coke wastewater, in which the initial chemical oxygen demand (COD) value and initial polycyclic aromatic hydrocarbons (PAHs) concentration were determined. The samples were then subjected to an oxidation procedure. Before the process, the pH was adjusted to 3.5–3.8. Next, the following doses of sodium carbonate—hydrogen peroxide (2/3): 1.2 g/L, 1.5 g/L and 2 g/L, and a constant dose of iron sulphate were added. The next step was exposing the samples to UV light for 6 min and separating the organic matrix from the samples of wastewater. After the tests, the final value of the COD and the final PAHs concentration were determined. The average content of organic pollutants in pretreated coke wastewater determined by the COD index was 538 mg/L, and after the oxidation process, the COD index decreased in the range from 9 to 29%. The efficiency of the degradation of the sum of 16 PAHs was varied and was in the range of 94–97.6%. The research results show that sodium carbonate—hydrogen peroxide (2/3) can be used for the degradation of organic pollutants, such as PAHs, in the modified Fenton process.

scholarly journals Research on Molecular Structure and Electronic Properties of Ln3+ (Ce3+, Tb3+, Pr3+)/Li+ and Eu2+ Co-Doped Sr2Si5N8 via DFT Calculation

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 1849
Author(s):  
Ziqian Yin ◽  
Meijuan Li ◽  
Jianwen Zhang ◽  
Qiang Shen
Keyword(s):  
Molecular Structure ◽  
Energy Level ◽  
Density Functional ◽  
Formation Energy ◽  
Electronic Band Structure ◽  
Blue Shift ◽  
Lanthanide Ions ◽  
Partial Replacement ◽  
Electronic Band ◽  
Charge Imbalance

We use density functional theory (DFT) to study the molecular structure and electronic band structure of Sr2Si5N8:Eu2+ doped with trivalent lanthanides (Ln3+ = Ce3+, Tb3+, Pr3+). Li+ was used as a charge compensator for the charge imbalance caused by the partial replacement of Sr2+ by Ln3+. The doping of Ln lanthanide atom causes the structure of Sr2Si5N8 lattice to shrink due to the smaller atomic radius of Ln3+ and Li+ compared to Sr2+. The doped structure’s formation energy indicates that the formation energy of Li+, which is used to compensate for the charge imbalance, is the lowest when the Sr2 site is doped. Thus, a suitable Li+ doping site for double-doped lanthanide ions can be provided. In Sr2Si5N8:Eu2+, the doped Ce3+ can occupy partly the site of Sr12+ ([SrN8]), while Eu2+ accounts for Sr12+ and Sr22+ ([SrN10]). When the Pr3+ ion is selected as the dopant in Sr2Si5N8:Eu2+, Pr3+ and Eu2+ would replace Sr22+ simultaneously. In this theoretical model, the replacement of Sr2+ by Tb3+ cannot exist reasonably. For the electronic structure, the energy level of Sr2Si5N8:Eu2+/Li+ doped with Ce3+ and Pr3+ appears at the bottom of the conduction band or in the forbidden band, which reduces the energy bandgap of Sr2Si5N8. We use DFT+U to adjust the lanthanide ion 4f energy level. The adjusted 4f-CBM of CeSr1LiSr1-Sr2Si5N8 is from 2.42 to 2.85 eV. The energy range of 4f-CBM in PrSr1LiSr1-Sr2Si5N8 is 2.75–2.99 eV and its peak is 2.90 eV; the addition of Ce3+ in EuSr1CeSr1LiSr1 made the 4f energy level of Eu2+ blue shift. The addition of Pr3+ in EuSr2PrSr2LiSr1 makes part of the Eu2+ 4f energy level blue shift. Eu2+ 4f energy level in EuSr2CeSr1LiSr1 is not in the forbidden band, so Eu2+ is not used as the emission center.

First-principles Studies of Phase Stability and the Neutral Atomic Vacancies in LiNbO3, NaNbO3 and KNbO3

2005 ◽  
Vol 902 ◽  
Author(s):  
Akio Shigemi ◽  
Takahiro Wada
Keyword(s):  
Enthalpy Of Formation ◽  
Density Functional ◽  
Formation Energy ◽  
Type Structure ◽  
Enthalpies Of Formation ◽  
Functional Formalism ◽  
Reducing Atmosphere ◽  
Perovskite Type Oxide ◽  
Formation Energies ◽  
Perovskite Type

AbstractWe overall evaluated the enthalpies of formation and the formation energies of neutral vacancies in ANbO3 (A = Li, Na, K) using a plane-wave pseudopotential method within a density functional formalism. The LiNbO3 phase with the LiNbO3-type structure was confirmed to have lower enthalpy of formation than that with perovskite- or ilmenite-type structure. The NaNbO3 (R3c) and KNbO3 (Bmm2 and R3m) phases with the lowest symmetry were found to have the lowest enthalpy of formation. The formation energy of a A vacancy was found to be the lowest under an oxidizing atmosphere and that of an O vacancy was found to be the lowest under a reducing atmosphere. The formation energy of a Nb vacancy was the highest under both oxygen-rich and -poor conditions. These results are in agreement with the empirical rule that B site defects in perovskite-type oxide do not exist.

Iron(III) Phthalocyanine-Modified Titanium Dioxide:  A Novel Photocatalyst for the Enhanced Photodegradation of Organic Pollutants

1998 ◽  
Vol 102 (47) ◽  
pp. 9397-9403 ◽  
Author(s):  
Koodali T. Ranjit ◽  
Itamar Willner ◽  
Stefan Bossmann ◽  
André Braun
Keyword(s):  
Titanium Dioxide ◽  
Organic Pollutants
Sign in / Sign up

Export Citation Format

Share Document