锐钛矿相TiO_2(001)/KOH界面的分子动力学模拟
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摘要
本文采用经典分子动力学对KOH溶液与锐钛矿相TiO_2(001)面的界面相互作用进行了模拟计算,结果表明,K~+主要分布于TiO_2(001)表面相邻两桥氧原子的中间位置并与之成键;K~+在TiO_2表面的吸附使其配位数和近表面扩散系数减少,并在近表面处形成有序结构。以KOH溶液离子数密度为基础计算得到液相部分的电荷、电场、电势分布,为了分析KOH对界面性质的影响,将只考虑水分子的溶液体系和纯水体系结果进行对比,结果发现,溶液的电荷密度和电场分布曲线峰值增大,电势收敛较慢,其原因为K~+集中在表面而OH~-随机分布于整个体系,由此造成体相阴离子相对过剩。
In this work, the interaction between anatase TiO_2(001) surface and KOH solution is studied by molecular dynamics simulations. Most of K~+ ions are shown to adsord at two bidentate sites, between two bridging oxygens in adjacent rows on the crystal surface. In addition, the coordination number and diffusion coefficient of K~+ are decreased due to its adsorption on TiO_2,resulting in an ordered structure in the interface. Based on the number density of K~+, O~(2-)and H~+,the interfacial electrostatic properties are analyzed. In order to obtain the effect of KOH on the interface, the electrostatic properties of H_2 O in solution are considered and compared with pure water system. The peaks of the charge density and the electric field distribution curves of KOH solution increase and the convergence of its potential becomes slow. The reason is that potassium ions are concentrated on the interface while hydroxyl ions are randomly distributed in the whole system, which lead to relative excess of anions in the bulk.
In this work, the interaction between anatase TiO_2(001) surface and KOH solution is studied by molecular dynamics simulations. Most of K~+ ions are shown to adsord at two bidentate sites, between two bridging oxygens in adjacent rows on the crystal surface. In addition, the coordination number and diffusion coefficient of K~+ are decreased due to its adsorption on TiO_2,resulting in an ordered structure in the interface. Based on the number density of K~+, O~(2-)and H~+,the interfacial electrostatic properties are analyzed. In order to obtain the effect of KOH on the interface, the electrostatic properties of H_2 O in solution are considered and compared with pure water system. The peaks of the charge density and the electric field distribution curves of KOH solution increase and the convergence of its potential becomes slow. The reason is that potassium ions are concentrated on the interface while hydroxyl ions are randomly distributed in the whole system, which lead to relative excess of anions in the bulk.
引文
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[23] Panagiotou G D, Petsi T, Bourikas K, et al. Mapping the Surface(hydr)Oxo-groups of Titanium Oxide and Its Interface with an Aqueous Solution:the State of the Art and a New Approach[J]. Advances in Colloid and Interface Science, 2008, 142(1):20-42
[2] Hadjiivanov K I, Klissirski D G. Surface Chemistry of Titania(Anatase)and Titania-Supported Catalysts[J].Chemical Society Reviews, 1996,25(1):61-69
[3] Linsebigler A L, L, G, Yates Jr J T. Photocatalysis on TiO_2 Surfaces:Principles, Mechanisms, and Selected Re-sults[J]. Chemical Reviews, 1995, 95(3):735-758
[4] Sang L, Zhao Y, Burda C. TiO_2 Nanoparticles as Functional Building Blocks[J]. Chemical Reviews, 2014,114(19):9283-9318
[5] Cheng J, Sprik M. Acidity of the Aqueous Rutile TiO_2(110)Surface From Density Functional Theory Based Molecular Dynamics[J]. Journal of Chemical Theory and Computation, 2010, 6(3):880-889
[6] Foissy A, Mpandou A, Lamarche J M, et al. Surface and Diffuse-Layer Charge at the TiO_2-electrolyte Interface[J].Colloids and Surfaces, 1982, 5(4):363-368
[7] Liu L M, Zhang C, Thornton G, et al. Structure and Dynamics of Liquid Water on Rutile TiO_2(110)[J]. Physical Review B, 2010, 82(16):161415
[8] Sumita M, Hu C, Tateyama Y. Interface Water on TiO_2Anatase(101)and(001)Surfaces:First-principles Study with TiO_2 Slabs Dipped in Bulk Water[J]. The Journal of Physical Chemistry C, 2010, 114(43):18529-18537
[9] Ashida M, Sasaki M, Kan H, et al. Kinetics of Proton Adsorption-Desorption at TiO_2-H_2O Interface by Means of Pressure-Jump Technique[J]. Journal of Colloid and Interface Science, 1978, 67(2):219-225
[10] Cachet H, Sutter E M M. Kinetics of Water Oxidation at TiO_2 Nanotube Arrays at Different pH Domains Investigated by Electrochemical and Light-Modulated Impedance Spectroscopy[J]. The Journal of Physical Chemistry C, 2015, 119(45):25548-25558
[11] Grinter D C R, Remesal E, Luo S, et al. Potassium and Water Coadsorption on TiO_2(110):OH-induced Anchoring of Potassium and the Generation of Single-site Catalysts[J]. The Journal of Physical Chemistry Letters, 2016,7(19):3866-3872
[12] Zhao Z, Li Z, Zou Z. Structure and Properties of water on the Anatase TiO_2(101)Surface:From Single-Molecule Adsorption to Interface Formation[J]. The Journal of Physical Chemistry C, 2012, 116(20):11054-11061
[13] Berendsen H J C, Postma J P M, Gunsteren W F V, et al. Molecular Dynamics with Coupling to an External Bath[J].The Journal of Chemical Physics, 1984, 81(8):3684-3690
[14] Sorenson J M, Hura G, Glaeser R M, et al. What Can X-ray Scattering Tell Us about the Radial Distribution Functions of Water[J]. The Journal of Chemical Physics,2000, 113(20):9149-9161
[15] Sun H, Ren P, Fried J R. The COMPASS Force Fields:Parameterization and Validation for Phosphazenes[J]. Computational and Theoretical Polymer Science, 1998, 8(1):229-246
[16] Sun H. COMPASS:An AB Initio Force-Fields Optimized for Condensed-Phase Applications Overview with Details on Alkane and Benzene Compounds[J]. The Journal of Physical Chemistry B, 1998, 102(38):7338-7364
[17] Sang L, Zhang Y, Wang J, et al. Correlation of the Depletion Layer with the Helmholtz Layer in the Anatase TiO_2-H_2O Interface via Molecular Dynamics Simulations[J]. Physical Chemistry Chemical Physics, 2016, 18(22):15427-15435
[18] Marcus Y. Ionic Radii in Aqueous Solutions[J]. Chemical Reviews, 1988, 88(8):1475-1498
[19]周健,陆小华,王延儒,等.离子水化的分子动力学模拟[J].化工学报,2000, 51(2):143-149ZHOU Jian, LU Xiaohua, WANG Yanru, et al. Molecular dynamics Simulation of ion Hydration[J]. Journal of Chemical Industry, 2000, 51(2):143-149
[20]黄子卿.电解质溶液理论导论[M].北京:科学出版社,1983HUANG Ziqing. Introduction to the Theory of Electrolyte Solution[M]. Beijing:Science Press, 1983
[21] Nada H, Kobayashi M, Kakihana M. Anisotropy in Conformation and Dynamics of a Glycolate ion Near the Surface of a TiO_2 Rutile Crystal between Its(001)and(110)Planes:a Molecular Dynamics Study[J]. The Journal of Physical Chemistry C, 2016, 120(12):6502-6514
[22] Calzado C J, San Miguel M A, Sanz J F. Theoretical Analysis of K Adsorption on TiO_2(110)Rutile Surface[J].The Journal of Physical Chemistry B, 1999, 103(3):480-486
[23] Panagiotou G D, Petsi T, Bourikas K, et al. Mapping the Surface(hydr)Oxo-groups of Titanium Oxide and Its Interface with an Aqueous Solution:the State of the Art and a New Approach[J]. Advances in Colloid and Interface Science, 2008, 142(1):20-42