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An examination of the effect of B- and P-doping and codoping on the electronic structure of anatase TiO2 by performing density functional theory calculations revealed the following: (i) B- or P-doping effects are similar to atomic undercoordination effects on local bond relaxation and core electron entrapment; (ii) the locally entrapped charge adds...
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... partial structures derived from the optimized B-doped TiO 2 with different doping concentrations are given in Fig 2. It is shown that high concentration (8.3% and 4.2%) doping does not distort the optimized crystal structure with elongation of the Ti-B bond. In the d eq direction, the distances between B and Ti atoms stretch from the initial 1.932 Å to 1.964 and 2.074 Å, meanwhile, in the d ap direction, the distances elongate from the initial 1.979 Å to 2.170 and 2.352 Å for 8.3% and 4.2% B-doping, respectively. ...
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... 16,18−26 Density functional theory calculations suggest that the occupation of interstitial sites or O substitution are more energetically favorable than substitution of Ti by B atoms. 24 It has been reported that the addition of boron to TiO 2 sol−gel precursors generally leads to interstitial Bdoping, together with the formation of B 2 O 3 on the surface of the TiO 2 particles. 16,19,27,28 Some studies have also shown that surface boron species can introduce residual charge, which can increase the number of surface OH groups, being them correlated with the incorporated B. 19,29 The positive influence of boron has also been related to changes in the TiO 2 structure as it could inhibit the growth of crystalline TiO 2 , leading to materials with increased surface area 30 and anatase content. ...
A series of nanostructured boron-TiO2 photocatalysts (B-X-TiO2-T) were prepared by sol-gel synthesis using titanium tetraisopropoxide and boric acid. The effects of the synthesis variables, boric acid amount (X) and crystallization temperature (T), on structural and electronic properties and on the photocatalytic performance for propene oxidation, are studied. This reaction accounts for the remediation of pollution caused by volatile organic compounds, and it is carried out at low concentrations, a case in which efficient removal techniques are difficult and costly to implement. The presence of boric acid during the TiO2 synthesis hinders the development of rutile without affecting the textural properties. X-ray photoelectron spectroscopy analysis reveals the interstitial incorporation of boron into the surface lattice of the TiO2 nanostructure, while segregation of B2O3 occurs in samples with high boron loading, also confirmed by X-ray diffraction. The best-performing photocatalysts are those with the lowest boron loading. Their high activity, outperforming the equivalent sample without boron, can be attributed to a high anatase and surface hydroxyl group content and efficient photo-charge separation (photoelectrochemical characterization, PEC), which can explain the suppression of visible photoluminescence (PL). Crystallization at 450 °C renders the most active sample, likely due to the development of a pure anatase structure with a large surface boron enrichment. A shift in the wavelength-dependent activity profile (PEC data) and the lowest electron-hole recombination rate (PL data) are also observed for this sample.
... B in SnO 2 can either occupy a substitutional site replacing Sn or it can be present at any interstitial site. Presence at the substitutional site is known to decrease the lattice volume, owing to smaller ionic radius of B than Sn, while there is an increase in lattice volume in interstitial cases (Li et al. 2016). From literature, it has been found that substitutional B is not favored, while interstitial or oxygen substitution is more commonly found. ...
Boron-doped SnO2 (B:SnO2) has been synthesized via a facile wet chemical method to deal with increasing energy demand and environment-related issues. Powder XRD confirmed the rutile phase of the synthesized B:SnO2 nanoparticles. Energy dispersive X-ray analysis and elemental mapping confirmed 1% B doping into SnO2 lattice. A red shift was observed during the analysis of Raman and FTIR spectral data. The bands in FTIR and Raman spectra confirmed the in-plane and bridging oxygen vacancies in SnO2 lattice introduced due to B doping. These nanoparticles showed proficiency in photocatalytic hydrogen generation and degradation of crystal violet (CV) and rhodamine B (RhB) dyes. The degradation of CV and RhB dyes in the presence of B:SnO2 NPs and ethane-1,2-diaminetetracetic acid (EDTA) was found to be 83 and ~ 100%, respectively. To escalate the efficiency of dye degradation, the experiment was performed with different sacrificial agents (EDTA, methanol, and triethanolamine). The maximum hydrogen production rate (63.6184 µmol g⁻¹ h⁻¹) was observed for B:SnO2 along with Pd as co-catalyst, and methanol and EDTA solution as sacrificial agents.
... However, due to the wide band-gap of 3.2 eV (for the anatase form) [6], TiO 2 has trivial response to the visible light (wavelength: 390-700 nm) [7,8] hindering the develop-ment of visible-light-driven photocatalysts based on TiO 2 for energy and environmental applications [6,9]. Various strategies [8,[10][11][12][13][14] such as (i) metal (e.g., transition metals Cu, Co) [11] with and non-metal doping (e.g., pblock elements N, B, F) [12,15,16] and (ii) crystal structure and morphology engineering [13,14] are being developed to adjust the band structure and trap states of TiO 2 with an aim to enhance the response of the TiO 2 -based photoelectrochemical materials in the visible region. Recently, the integration of plasmonic gold or silver nanoparticles (NPs) with TiO 2 [8,[17][18][19][20][21][22] have been proposed to enhance the photocatalytic and photovoltaic activity in the visible region due to the strong surface plasmon resonance (SPR) excitation of such metal NPs, by which can enhance the concentration of charge carriers. ...
A strategy of intensifying the visible light harvesting ability of anatase TiO2 hollow spheres (HSs) was developed, in which both sides of TiO2 HSs were utilised for stabilising Au nanoparticles (NPs) through the sacrificial templating method and convex surface-induced confinement. The composite structure of single Au NP yolk-TiO2 shell-Au NPs, denoted as Au@Au(TiO2, was rendered and confirmed by the transmission electron microscopy analysis. Au@Au(TiO2 showed enhanced photocatalytic activity in the degradation of methylene blue and phenol in aqueous phase under visible light surpassing that of other reference materials such as Au(TiO2 by 77% and Au@P25 by 52%, respectively, in phenol degradation.
... [24][25][26][27][28][29] The work function for metallic surface (or ionization potential for semiconducting or insulating surface) is known as the most important feature of the surface potential. [30][31][32][33][34][35] Furthermore, the significant inverse relationship between ionization potential and polarizability has been observed in previous studies. Dmitrieva et al. were first to predict this feature for atomic systems by the use of a statistical model. ...
The potential distribution and work function of a graphene surface modified by various types of silanes are investigated by first principle quantum mechanical calculations to establish its surface hydrophobicity hierarchy. It is found that work function relies on the electronegativity of atoms on silane. Localization feature of interaction between silane and graphene surface is demonstrated by the electron density difference. Work function is demonstrated to be a critical quantity in understanding surface polarizability and thereby the surface wetting property. By performing contact angle measurements experimentally using water as the probe fluid, surfaces grafted with different silanes show hydrophobicity variation that is found to follow the reverse trend as that of the proposed surface polarizability obtained through the work function calculation. The work function-dependent contact angle can be fitted with a linear equation.
... DFT calculation reports that boron will not substitute Ti atom. Instead, it will either substitute O atom or occupy the interstitial sites or both are possible [24]. However, the higher concentration of boron doping in TiO 2 nanotubes can form B 2 O 3 species [25] and its significant presence in TiO 2 will reduce the crystallinity of overall nanostructures [26]. ...
... The tauc plot analysis of the samples has been shown in Fig. 3(a), where the band gaps of TNT and B-TNT are 3.3 eV and 3.1 eV, respectively. The boron doping leads to a decrease in the band gap of TiO 2 nanotubes which is in good agreement with the earlier reported study [24]. The absorption properties of TiO 2 nanotubes are in good agreement with nanostructure analysis because the energy band gap of nanotubes decreases with increase in tube diameter (d nm) by relation, [44]. ...
... The absorption edge of the tauc plot in B-TNT sample is sharper than that of TNT, which substantiates the dominating nature of direct band gap material. The red shift in the absorption spectra of the B-TNT can be attributed to the crystal geometry modification of the electronic structure [45,24]. ...
The present study highlights the significant impact of trace level doping of boron in titanium dioxide (TiO2) nanotubes by investigating the structural, optical and electronic properties of samples, TNT and B-TNT. TEM analysis of boron-doped sample confirms the formation of crystalline nanotube structures and the trace level quantification of boron was confirmed by XPS analysis, where B shows feature of Ti–O–B bonding. Raman analysis revealed that the rutile phase becomes prominent after boron doping and Raman bands shift towards higher wavenumber was observed with increase in the tube diameter. The boron incorporation in TiO2 nanotubes reduces the band gaps from 3.3 eV to 3.1 eV and the mid-gap states were created within the band gap of the B-TNT sample. The change in valance band position from 2.5 eV to 2.9 eV after boron doping significantly changed the Fermi level position in TiO2 nanotubes. The work function of pristine and boron doped TiO2 samples are observed as 4.23 eV and 4.27 eV, respectively, as measured by Kelvin probe force microscopy. Here, we have investigated the band alignment of TNT and B-TNT by using state-of-the-art material characterization surface sensitive techniques. It can also be concluded that the electron affinity of the B-TNT sample is enhanced ∼4.07 eV than that of TNT ∼ 3.43 eV. The type –II band alignment is observed to be in between TNT and B-TNT with a valence band offset (VBO) ∼ 0.4 eV and conduction band offset (CBO) ∼ 0.6 eV.
... Moreover, the Fermi level is shifted up in the band structure showing consistency with reported data [25,26]. Substitutional P doping at O sites would not change the location of Fermi level in the band gap [27], while replacing the lattice Ti atom by P atom shifted the Fermi level from top of the valence to the bottom of conduction band. Tuning the band gap will improve the absorbance of doped TiO 2 . ...
Using the hydrothermal method, a P-doped TiO2 nano-catalyst is prepared for widening the application spectrum of TiO2. The synthesized samples are investigated using XRD, TEM, and UV–visible absorption spectra. A P-doped TiO2 system is simulated and calculations for geometrical structure, electronic and optical properties are performed based on density functional theory. Comparison of the electronic band structure of anatase TiO2 before and after doping verified that doping tuned the band structure. XRD patterns revealed that pure anatase phase is the only phase in case of pure and doped samples. TEM observations reveal spherical morphology. The P doped TiO2 experimentally as well as theoretically responded to visible light confirming the band structure findings. Photocatalytic activity of the doped samples drastically improved compared to bare TiO2.
Several doping processes are being investigated for the enhancement and efficient utilization of TiO2 properties with increased focus on the crystallinity and mobility of TiO2 nanorods. In this study, boron (B) was chosen as the dopant for its small orbital states of B3+ when compared to Ti4+. The B-doped TiO2 nanorods were fabricated on pre-cleaned fluorine-doped tin oxide substrate using hydrothermal method. The structural characterization was done by X-ray diffraction spectroscopy with diffraction angle fixed at 0.5° which was further confirmed by Raman spectroscopy. X-ray photoelectron spectroscopy was employed to analyse the elemental composition of the samples while the morphological characterization was achieved with the use of field-emission scanning electron microscopy and transmission electron microscopy. The absorption spectra were obtained using UV–Visible spectroscopy and the bandgap calculated from Tauc’s plot. The photocurrent properties were analysed by photoelectrochemical-based self-powered photodetector. No significant changes were observed in the morphology of the TiO2 nanorods after doping. Both the crystallinity and mobility of TiO2 nanorods from the B atom were increased. X-ray photoelectron and UV–Vis spectroscopy both confirmed that B dopant was present in interstitial and substitutional positions in the TiO2 lattice even in low B dopant concentration. The photocurrent analysis indicates increased output current from 5.0 µA of pristine nanorods, to 16.5 µA of 1.00 wt% B-doped rutile TiO2 nanorods, implying their enhanced electron transport. This was also proven by electrochemical impedance spectroscopy analysis where 1.00 wt% of B-doped TiO2 showed the lowest electron recombination rate at electrolyte/working electrode interface. The results of this study can be used to improve the activities of solar cells, UV photodetector, or for photocatalytic applications.
