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Surface Photocatalytic Research of Fe -doped TiO2 (001) Based On the First-principles
摘要： In this paper,the first-principles based on density functional theory was used to study the Fe/TiO2(001) band gap width and adsorption energy of C6H6 molecules at different positions on the surface of the molecule with different doping methods and different Fe content. Calculation of the band structure and density of states of Fe-doped TiO2 nanoparticles shows that, the surface gap doping is more favorable than the substitution doping to reduce the band gap of TiO2,and when the doping concentration is 6.122%,the maximum reduction of the band gap width is 59.3% higher than that of pure TiO2.According to the comparement of adsorption energy, it works out that the benzene molecule is mainly about horizontal adsorption on the surface of TiO2(001).Within the scope of the study, with the increase of Fe doping concentration, The adsorption energy does not decrease as the band gap, when the Fe atoms doping concentration is 4.167%,the maximum increase of adsorption energy is 63.2%.
关键词： photocatalytic,Fe-doped TiO2,band gap,first-principles,adsorption energy
更新于2025-09-23 15:21:01
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Thermal darkening of one-dimensional photonic crystal containing tellurium suboxide
摘要： The purpose of this study is to experimentally and theoretically evaluate the optical properties of a one-dimensional photonic crystal (PC) with a defect layer before and after an annealing procedure. A sputtering technique with high index (TeOx) and low index (SiO2) materials was used to fabricate the 1D PC with a defect layer. The chemical and structural analysis of a single layer TeOx thin film was evaluated by X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and X-Ray Diffraction (XRD). The optical constant of the single layer was also determined based on the envelope method from transmittance spectra measured by ultraviolet visible near-infrared spectrophotometry (UV-VIS-NIR). The measured reflectance spectra of the 1D PC were compared with the results simulated using the transfer matrix method (TMM) before and after the annealing procedure. A photonic bandgap (PBG) appears within the desired, near-infrared (NIR), region. The defect mode in the 1D PC was observed at λ = 1455 nm within the PBG of λ = 1235–1723 nm (Δλ = 488 nm). The reflectance spectra overall shifted toward longer wavelength due to thermal darkening effect resulting from the thermally induced optical property changes.
关键词： Photonic band gap,One-dimensional photonic crystals,Tellurium suboxide,Thermal darkening,Defect layer
更新于2025-09-23 15:21:01
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Temperature Dependence of Phonon Modes, Optical Constants, and Optical Band Gap in Two-Dimensional ReS2 Films
摘要： Effects of temperature on the optical properties of the large area ReS2 films (ten layers), which is prepared by chemical vapor deposition on SiO2/Si substrates, have been investigated by Raman and reflectance spectra. The phonon frequencies of eighteen Raman modes redshift about 3 cm-1 with increasing the temperature from 140 K to 320 K. The optical constants (n and k) at a photon energy region of 0.46-6.52 eV are obtained, and the values blue-shift with increasing temperature. Four interband transitions (Ep1, Ep2, Ep3, and Ep4) are observed at 1.53 eV, 2.98 eV, 4.25 eV, and 5.37 eV at 303 K, and the values increase with increasing the temperature. The physical origins have been assigned to the different band-to-band direct electronic transitions. The optical band gap of the ReS2 films increases from 1.36 eV at 303 K to 1.38 eV at 383 K. Based on the first-principles calculation results, the band gap increases from 1.32 eV at a normal lattice constant to 1.40 eV at 1.1 times lattice constant. This is because the energy levels present the tendencies of degeneracy, which due to the coupling between Re 5d orbital and S 3p orbital is weaker and the energy level splitting is smaller with increasing temperature.
关键词： optical constants,ReS2 films,2D materials,phonon modes,optical band gap
更新于2025-09-23 15:21:01
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Combustion synthesis and photoelectrochemical characterization of gallium zinc oxynitrides
摘要： We report a rapid combustion synthesis method for producing band gap tunable gallium zinc oxynitrides, a material of interest for water splitting applications. By varying the ratio of zinc and gallium, we can tune the band gap from 2.22 to 2.8 eV. Furthermore, nitrogen can be incorporated up to nearly 50% via replacement of oxygen without the need for high temperatures or an additional ammonolysis step. X-ray photoelectron spectroscopy (XPS) and EDX analysis suggests a preferential segregation of Zn to the surface of the as-synthesized particles, though the surface Ga/Zn molar ratio in the as-synthesized particles is correlated with the Ga/Zn molar ratio of the precursor materials. Photoelectrochemical measurements show that the oxynitride powders are photoactive under both AM1.5 and visible-only (k . 435 nm) irradiation. Hydrogen and oxygen were both evolved in half-reaction experiments under simulated AM1.5 irradiation without externally applied bias, although addition of an OER catalyst did not enhance the rate of oxygen formation, suggesting that intra- and interparticle recombination are signi?cant.
关键词： water splitting,photoelectrochemical,gallium zinc oxynitrides,band gap tuning,combustion synthesis
更新于2025-09-23 15:21:01
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In situ fluorine doped ZrO2?x nanotubes for efficient visible light photocatalytic activity
摘要： The F-doped ZrO2?x nanotubes are synthesized by anodic oxidization in a F-containing electrolyte and following a low temperature annealing process. The F-doped ZrO2?x nanotubes exhibit a dramatic increase in visible light absorption and efficient visible light photocatalytic activity which are not possessed to normalized ZrO2. The fluorine in anodic ZrO2 nanotubes plays a vital role in the formation of abundant anion vacancies during the annealing. Combining the doping effect of the residual fluorine element, the band gap of the F-doped ZrO2?x nanotubes reduced from 5.13 to 2.35 eV. Moreover, the transient photocurrent response plots and the photocatalytic experiments reveal the highly effective electrons–holes separation of the F-doped ZrO2?x nanotubes and enhanced visible-light photocatalytic degradation for RhB. The degradation rate of RhB in the presence of the F-doped ZrO2?x nanotubes catalyst has reached up to 83% under 2 h low-power LED light irradiation. In addition, the possible photocatalytic mechanism of the F-doped ZrO2?x nanotubes has been proposed via studying the band structure. It is believed that the F-doped ZrO2?x nanotubes will have a bright future for sustainable energy sources and cleaning environment.
关键词： oxygen vacancies,F-doped ZrO2?x nanotubes,anodic oxidization,visible light photocatalytic activity,band gap narrowing
更新于2025-09-23 15:21:01
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The Optical Properties of Metamaterial-Superconductor Photonic Band Gap With/Without Defect Layer
摘要： In the present work, we have investigated theoretically the optical properties of a new one-dimensional defected photonic crystal structure (1DDPC). The structure is composed of alternating layers of metamaterial (double-negative material) and high Tc superconductor material called Hg1223 defected with a dielectric material (SiO2) at the center of the structure. The transmittance spectra of the proposed structure are obtained by using the transfer matrix method (TMM). We noticed that multiple transmittance peaks within the photonic band gap (PBG) as the thickness of defect layer increases. The tunable filtering feature is obtained by varying the thicknesses of metamaterial and superconductor layer. In addition, the defect peak is red shifted as well as photonic band gap tuned to low-frequency region. Our structure is sensitive to the variation of the angle incidence. Also, defect mode shown to be blue shifted as the angle of incidence increases. The tunable filtering properties are very useful in the optoelectronic applications.
关键词： Metamaterial,Photonic band gap,TMM,Superconductor
更新于2025-09-23 15:21:01
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Facile, rapid, one-pot synthesis of hydrogenated TiO2 by using an atmospheric-pressure plasma jet submerged in solution
摘要： We report a simple method for the synthesis of hydrogenated TiO2 (H-TiO2) by submerging an atmospheric-pressure plasma jet in a titanium precursor solution. The synthesized H-TiO2 demonstrates improved visible light absorption and electrical conductivity due to a decreased work function and narrowed band gap. Our plasma system has significant benefits compared to previously reported hydrogenation methods. It offers a facile, one-pot synthesis process, rapid synthesis time, and ease of mass production. We expect the plasma system to be a promising technology for the synthesis of H-TiO2, and believe this method has potential for use in new environmental and optoelectronic applications.
关键词： Synthesis,Titanium dioxide,Plasma,Band gap,Hydrogenation
更新于2025-09-23 15:21:01
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Graphene/TiO2 nanocomposite electrodes sensitized with tin sulfide quantum dots for energy issues
摘要： In this work, graphene (Gr)/TiO2 nanocomposite electrodes sensitized with tin sulfide quantum dots (SnS QDs) for energy issues have been investigated. Different sizes of SnS QDs as non-toxic and earth-abundant semi-conducting materials are synthesized onto Gr/TiO2 nanocomposite electrodes using successive ionic layer adsorption and reaction (SILAR) technique for “n” cycles (n: 1 to 8). The structural properties of the prepared SnS (n) QDs photoanodes are studied using an X-ray diffractometer. The XRD measurements ensure the formation of the crystalline structure of orthorhombic SnS QDs. The optical properties of the synthesized SnS(n) QDs photoanodes are characterized using a UV–visible spectrophotometer. The estimated direct (indirect) energy band gap (Eg) of the prepared SnS(n) photoanodes is tuned from 2.36 (1.57) eV to 1.76 (1.30) eV by controlling the number of SILAR cycles from 1 to 8. The photovoltaic performance of the assembled SnS(n) quantum dots sensitized solar cells (QDSSCs) has been studied under a solar power illumination of AM1.5 conditions. The optimal photovoltaic performance of the assembled SnS(n) QDSSCs is achieved at 6 SILAR deposition cycles. As compared with previous studies, enhancement of 48% in the energy conversion efficiency η has been achieved due to the active Gr incorporation. SnS(n) QDSSCs shows high reproducibility and sensitivity undercutting ON-OFF the solar illumination. Gr plays the role of kids slide for the photo-generated electrons and facilitates their transportation.
关键词： Graphene/TiO2,Reproducibility of QDSSCs,Recombination suppression,Tuning band gap,SnS solar Cell
更新于2025-09-23 15:19:57
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Strain engineering of ferroelectric KNbO <sub/>3</sub> for bulk photovoltaic applications: an insight from density functional theory calculations
摘要： A large ferroelectric (FE) polarization and low bandgap are essential to improving the bulk photovoltaic response which is the generation of photocurrent in the polar non-centrosymmetric materials such as FE perovskite oxides. Among various perovskite oxides, Potassium Niobate (KNbO3, KNO) is a promising FE material for bulk photovoltaic applications as its bandgap and polarization can be tuned effectively by strain, doping, or by applying an electric field. In this work, using the density functional theory calculations, we present an insight into the strain engineering of polarization, band structure, and optical properties of the cubic (C), tetragonal (T), and orthorhombic (O) structures of KNO. The tensile and compressive strain under the triaxial, biaxial, and uniaxial conditions are applied along the direction parallel and perpendicular to the polar axis of KNO structures. We find that the bandgap decreases along with a substantial increment of polarization on the application of tensile strain along the direction parallel to the polar axis. In T (O) phase at +2% strain, the polarization increases by 18 μC cm?2 (14 μC cm?2) in triaxial, 26 μC cm?2 (16 μC cm?2) in biaxial, and 29 μC cm?2 (29 μC cm?2) in uniaxial conditions with a considerable decreasing of bandgap with respect to zero strain condition. Therefore, wisely applying the tensile strain along the direction parallel to the polar axis, the photovoltaic efficiency of KNO can be improved.
关键词： density functional theory,bulk-photovoltaic,band gap,strain,polarization
更新于2025-09-23 15:19:57
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Investigation of structural, electronic, optical and thermoelectric properties of Ethylammonium tin iodide (CH3CH2NH3SnI3): An appropriate hybrid material for photovoltaic application
摘要： Hybrid halide Perovskites have been emerging as the innovative candidate in the development of optoelectronic devices. Ethyl-ammonium based hybrid halide perovskites have been admirable compounds regarding low band gap, high stability and non-toxic properties instead of methyl-ammonium based hybrid halide perovskites. Herein, we have investigated structural, electronic, optical and thermoelectric (TE) properties of ethyl-ammonium tin iodide (CH3CH2NH3SnI3) by full-potential linearized augmented plane wave plus local orbital (FP-LAPW t lo) method as implemented in the WIEN2k code within the density functional theory (DFT). The PBE-GGA, PBE-sol-GGA and TB-mBJ-GGA exchange-correlation potentials have been used to calculate the density of states and band structure of ethyl ammonium tin iodide (EASnI3) and found that it is a direct band gap semiconductor. We have calculated optical parameters such as dielectric function, absorption coefficient, refractive index, extinction coefficient, Eloss, optical reflectivity and optical conductivity for photon energies in the range 0–25 eV. We have also calculated transport coefficients (Seebeck coefficient, the figure of merit, power factor, electrical conductivity, thermal conductivity) as a function of carrier concentration, chemical potential and temperature. Most of the investigated parameters are being reported for the first time. The present study establishes that ethyl-ammonium tin iodide (EASnI3) offers high absorption coefficient, high Seebeck coefficient, etc. This makes it a prospective material for cost effective photovoltaic device applications to overcome environmental instabilities.
关键词： Dielectric constant,Absorption coefficient,Ethyl-ammonium based hybrid perovskite,Band gap
更新于2025-09-23 15:19:57