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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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Tailoring of graphene quantum dots for toxic heavy metals detection
摘要： The sensitivity of graphene quantum dots towards toxic heavy metals (THMs; Cd, Hg, Pb) can be improved through doping with nitrogen at the vacant site defects. Using density functional theory, we investigate the adsorption of THMs on the graphene quantum dots (GQDs) and nitrogen-coordinated defective GQDs (GQD@1N, GQD@2N, GQD@3N and GQD@4N) surfaces. Thermochemistry calculations reveal that the adsorption of Pb atom on the surfaces is more favorable than Cd and Hg adsorption. The decoration of the vacant defects with nitrogen on the GQD surface substantially increases the charge transfer and adsorption energy values of THMs on the GQD surface (GQD@4N > GQD@3N > GQD@1N > GQD@2N > GQD). The charge transfer and adsorption energy of lead on each of these surfaces are greater than those of cadmium and mercury (Pb > Cd > Hg). Quantum theory of atoms in molecules analysis and non-covalent interaction plots further validate this result while also confirming that Pb atom has a partially covalent and electrostatic nature of interaction at the nitrogen-coordinated vacant site defects. The electron density values—a criterion of bond strength—for the THM...N interactions are greater than for the THM…C interactions, confirming the observed adsorption energy trends of the THMs on the surfaces. The lowering of the HOMO–LUMO energy gap of the surfaces follows the order Pb > Cd > Hg and also results in increased electrical conductivity, which are consistent with the calculated adsorption energy trends. Significant changes in the energy gap and electric conductivity of the surfaces upon THMs adsorption make them promising sensors for metal detection. Finally, time-dependent density functional theory calculations showed that changes such as peak shifts, peak quenching and appearance of new peaks are seen in the UV–visible absorption spectra of the surfaces upon adsorption of THMs, wherein the shifts in peaks correspond to the magnitude of adsorption energy of THMs on the surfaces. These results should motivate the experimentalists towards using rational and systematic modulation of surfaces as sensors for heavy metal detection.
关键词： Adsorption energy,Toxic heavy metals,Charge transfer,UV–visible absorption spectra,Nitrogen doping,Density functional theory,HOMO–LUMO energy gap,Graphene quantum dots
更新于2025-09-16 10:30:52
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Research on residual gas adsorption on surface of InGaAs photocathode
摘要： The negative electron a?nity InGaAs photocathode is an important part of the infrared vacuum detector. The article focuses on the adsorption of residual gas in the preparation of InGaAs photocathodes. The impact of the adsorbates on the generation of negative electron a?nity was calculated and discussed. Models of InGaAs surface with residual gas were built and the work function, charge transfer, dipole and the formation energy have been analyzed based on the ?rst principles. The dipole from the surface to the residual gas molecule was generated by the charge transfer. The surface work function went up followed. The biggest increment came up to 0.410 eV, which is caused by the adsorption of CO2. The photoelectrons escape was restrained. As a result, three chemical cleaning methods were proposed to clean the InGaAs surface. It is found that oxide is more stable to be wiped o? than the other residual gas molecule. So a further treatment needs to be raised.
关键词： Adsorption energy,InGaAs surface,Residual gas,Charge transfer
更新于2025-09-10 09:29:36