Browsing by Author "Shan, Bin"
Now showing 1 - 6 of 6
- Results Per Page
- Sort Options
Item Enhanced Photosensitized Activity of a BiOCl-Bi₂WO₆ Heterojunction by Effective Interfacial Charge Transfer(2013-10-02) Yang, W.; Ma, B.; Wang, W.; Wen, Y.; Zeng, D.; Shan, BinA BiOCl-Bi₂WO₆ heterojunction with a chemically bonded interface was synthesized via a facile one-step solvothermal method. A series of characterization techniques (XRD, XPS, TEM, SEM, EDS etc.) confirmed the existence of a BiOCl-Bi₂WO₆ interface. The heterojunction yielded a higher photodegradation rate of Rhodamine B under visible light irradiation compared to its individual components. Theoretical studies based on density functional theory calculations indicated that the enhanced photosensitized degradation activity could be attributed to the favorable band offsets across the BiI-O-BiII bonded interface, leading to efficient interfacial charge carrier transfer. Our results reveal the photosensitized mechanism of BiOCl-Bi₂WO₆ heterojunctions and demonstrate their practical use as visible-light-driven photocatalytic materials.Item A First-Principles Study of Sodium Adsorption and Diffusion on Phosphorene(Royal Soc Chemistry) Liu, Xiao; Wen, Yanwei; Chen, Zhengzheng; Shan, Bin; Chen, RongThe structural, electronic, electrochemical as well as diffusion properties of Na doped phosphorene have been investigated based on first-principles calculations. The strong binding energy between Na and phosphorene indicates that Na could be stabilized on the surface of phosphorene without clustering. By comparing the adsorption of Na atoms on one side and on both sides of phosphorene, it has been found that Na-Na exhibits strong repulsion at the Na-Na distance of less than 4.35 Å. The Na intercalation capacity is estimated to be 324 mA h g⁻¹ and the calculated discharge curve indicates quite a low Na⁺/Na voltage of phosphorene. Moreover, the diffusion energy barrier of Na atoms on the phosphorene surface at both low and high Na concentrations is as low as 40-63 meV, which implies the high mobility of Na during the charge/discharge process.Item Modulation of Contact Resistance between Metal and Graphene by Controlling the Graphene Edge, Contact Area, and Point Defects: An Ab Initio Study(Amer Inst Physics) Ma, Bo; Gong, Cheng; Wen, Yanwei; Chen, Rong; Cho, Kyeongjae; Shan, BinA systematic first-principles non-equilibrium Green's function study is conducted on the contact resistance between a series of metals (Au, Ag, Pt, Cu, Ni, and Pd) and graphene in the side contact geometry. Different factors such as the termination of the graphene edge, contact area, and point defect in contacted graphene are investigated. Notable differences are observed in structural configurations and electronic transport characteristics of these metal-graphene contacts, depending on the metal species and aforementioned influencing factors. It is found that the enhanced chemical reactivity of the graphene due to dangling bonds from either the unsaturated graphene edge or point defects strengthens the metal-graphene bonding, leading to a considerable contact resistance reduction for weakly interacting metals Au and Ag. For stronger interacting metals Pt and Cu, a slightly reduced contact resistance is found due to such influencing factors. However, the wetting metals Ni and Pd most strongly hybridize with graphene, exhibiting negligible dependence on the above influencing factors. This study provides guidance for the optimization of metal-graphene contacts at an atomic scale.Item Study of Structural, Electronic and Optical Properties of Tungsten Doped Bismuth Oxychloride by DFT Calculations(Royal Soc Chemistry) Yang, Wenjuan; Wen, Yanwei; Chen, Rong; Zeng, Dawen; Shan, BinFirst-principle calculations have been carried out to investigate structural stabilities, electronic structures and optical properties of tungsten doped bismuth oxychloride (BiOCl). The,structures of substitutional and interstitial tungsten, and in the form of WO6-ligand-doped BiOCl are examined. The substitutional and interstitial tungsten doping leads to discrete midgap states within the forbidden band gap, which has an adverse effect on the photocatalytic properties. On the other hand, the, WO6-ligand-doped BiOCl structure induces a continuum of hybridized states in the forbidden gap, which favors transport of electrons and holes and could result in enhancement of visible light activity. In addition, the band gap of WO6-BiOCl decreases by 0.25 eV with valence band maximum (VBM) shifting upwards compared to that of pure BiOCl. By calculating optical absorption spectra of pure BiOCl and WO6-ligand-doped BiOCl structure, it is found that the absorption peak of the WO6-ligand-doped BiOCl structure has a red shift towards visible light compared with that of pure BiOCl, which agrees well with experimental observations. These results reveal the tungsten doped BiOCl system as a promising material in photocatalytic decomposition of organics and water splitting under sunlight irradiation.Item Tunable H₂ Binding on Alkaline and Alkaline Earth Metals Decorated Graphene Substrates from First-Principles Calculations(Pergamon-Elsevier Science Ltd, 2017-04-13) Wen, Yanwei; Xie, Fan; Liu, Xiaolin; Liu, Xiao; Chen, Rong; Cho, Kyeongjae; Shan, Bin; 0000-0003-2698-7774 (Cho, K); 369148996084659752200 (Cho, K); Cho, Kyeongjae; Shan, BinBased on first-principles calculations, the H-2 adsorptions onto six types of modified graphene substrates decorated with light metals (Li, Na, K, Be, Mg, Ca) are investigated to shed light on the factors affecting the H-2 binding energies. It is demonstrated that the introduction of defects and dopants into graphene substrates is essential to prevent the metal clustering and achieve dispersed metal atoms desirable for H-2 adsorption. The interaction between H-2 and alkali/alkali-earth metal decorated graphene systems is attributed to the electrostatic effect induced by polarized dipole-dipole interaction. Via introducing defects and hetero-atoms to modify the electronegativity of the local structure, the H-2 adsorption energy can be tuned by choosing the combination of suitable metals and substrates. The calculated H-2 binding strength is positively correlated to the charge transfer from the metal to the substrates and the dipole momentum of metal decorated substrates. Compared the cases with different metals decoration, Mg and Ca are expected to the most promising candidates for multiple H-2 adsorptions.Item Tuning the Structure of Bifunctional Pt/SmMn₂O₅ Interfaces for Promoted Low-Temperature CO Oxidation Activity(Royal Society of Chemistry, 2019-01-30) Liu, X.; Yang, J.; Shen, G.; Shen, M.; Zhao, Y.; Cho, Kyeongjae; Shan, Bin; Chen, R.; 0000-0003-2698-7774 (Cho, K); 0000-0001-7800-0762 (Shan, B); Cho, Kyeongjae; Shan, BinThe interfacial structure of metal-oxide composite catalysts plays a vital role in heterogeneous catalysis, which is crucial to the adsorption and activation of reactants. Herein, the interfacial effects of bare and Fe/Co/Ni doped Pt/SmMn₂O₅ mullite oxide supported Pt clusters on CO oxidation have been investigated by first-principles based microkinetics analysis. A robust formation of Pt/Mn₂ trimer structures is demonstrated at the bifunctional interfaces irrespective of the Pt_{n} cluster's size, which can provide spatially separated sites for CO adsorption and O₂ dissociation. The binding strength of CO at the interfacial Pt sites is in the optimal range due to the charge transfer from Pt clusters to oxide, while the strong polarization of Mn₂ dimers induced by Pt clusters with stable three-dimensional morphologies can lower the energy barrier of O₂ dissociation. Based on the microkinetics analysis, the O₂ dissociation is the rate-determining step in the full CO oxidation cycle, and the introduction of Mn-Fe hetero-dimers at the interface is predicted to further enhance the low temperature CO oxidation activity of Pt/SmMn₂O₅ catalysts. © The Royal Society of Chemistry 2019.