锐钛矿TiO_2(101)表面电子能带结构的理论研究
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摘要
二氧化钛作为一种理想的光催化和光电转换半导体材料,受到了广泛的关注和研究,其表面的电子能带结构作为其本征的化学性质之一,决定着表面上氧化还原反应发生的可能性.对二氧化钛表面电子能带结构进行深入研究对于我们从微观上认识并改良二氧化钛这一光电催化材料,以及进一步开发利用更好的光催化材料都具有非常好的指导意义.本论文采用密度泛函理论,计算研究了锐钛矿TiO_2(101)表面的电子能带结构,并通过与金红石TiO_2(110)晶面的对比,系统分析了两个表面电子能带结构的不同以及水分子的溶剂化作用对电子能带结构的影响.
As one of the most commonly-used materials for photocatalysis and solar energy conversion,titanium dioxide(TiO_2)has been extensively studied for more than 40 years.Its photoelectrochemical activity crucially depends on the band positions at the interface.In this work,the valence band maximum(VBM) and conduction band minimum(CBM) of a model TiO_2 surface are com puted using the standard work function method at the level of Perdew-Burke-Ernzerhof(PBE) density functional,which are then converted to the scale of the standard hydrogen electrode(SHE) by subtracting the absolute SHE potential.Comparing with the rutile TiO_2(110) surface,we find a similar upshift in the VBM and CBM upon the adsorption of water molecules on the anatase TiO_2(101)surface,and the band gap error intrinsic to the PBE functional can be mainly attributable to mis-positioning of the VBM.In addition,in contrast to the finding on the rutile TiO_2(110) surface that the adsorption of 1 monolayer water largely recovers the band alignment of the aqueous interface,our preliminary calculations indicate that on the anatase TiO_2(101) surface there is a considerable difference between the simplified model with the adsorption of 1 monolayer water and the fully solvated interface,suggesting the necessity to include the water molecules beyond the first adsorption layer in order to realistically represent the anatase TiO_2 water interface.
As one of the most commonly-used materials for photocatalysis and solar energy conversion,titanium dioxide(TiO_2)has been extensively studied for more than 40 years.Its photoelectrochemical activity crucially depends on the band positions at the interface.In this work,the valence band maximum(VBM) and conduction band minimum(CBM) of a model TiO_2 surface are com puted using the standard work function method at the level of Perdew-Burke-Ernzerhof(PBE) density functional,which are then converted to the scale of the standard hydrogen electrode(SHE) by subtracting the absolute SHE potential.Comparing with the rutile TiO_2(110) surface,we find a similar upshift in the VBM and CBM upon the adsorption of water molecules on the anatase TiO_2(101)surface,and the band gap error intrinsic to the PBE functional can be mainly attributable to mis-positioning of the VBM.In addition,in contrast to the finding on the rutile TiO_2(110) surface that the adsorption of 1 monolayer water largely recovers the band alignment of the aqueous interface,our preliminary calculations indicate that on the anatase TiO_2(101) surface there is a considerable difference between the simplified model with the adsorption of 1 monolayer water and the fully solvated interface,suggesting the necessity to include the water molecules beyond the first adsorption layer in order to realistically represent the anatase TiO_2 water interface.
引文
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[2]Xiong G,Shao R,Droubay T C,et al.Photoemission electron microscopy of Ti O2anatase films embedded with rutile nanocrystals[J].Advanced Functional Materials,2007,17(13):2133-2138.
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[13]Rodriguez H F,Tranca D C,Szyja B M,et al.Water splitting on Ti O2-based electrochemical cells:A small cluster study[J].Journal of Physical Chemistry C,2016,120(1):437-449.
[14]Pan J,Liu G,Lu G Q,et al.On the true photoreactivity order of{001},{010},and{101}facets of anatase Ti O2crystals[J].Angewandte Chemie-International Edition,2011,50(9):2133-2137.
[15]Cheng J,Sulpizi M,Sprik M.Redox potentials and p Ka for benzoquinone from density functional theory based molecular dynamics[J].The Journal of Chemical Physics,2009,131(15):154504.
[16]Trasatti S.The absolute electrode potential:An explanatory note[J].Pure and Applied Chemistry,1986,58(7):955-966.
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[20]The CP2K developers group.http://cp2k.berlios.de(accessed Feb 2010).
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[24]Vande Vondele J,Hutter J.Gaussian basis sets for accu rate calculations on molecular systems in gas and condensed phases[J].Journal of Chemical Physics,2007,127(11):114105.
[25]Cheng J,Sprik M.Acidity of the aqueous rutile Ti O2(110)surface from density functional theory based molecular dynamics[J].Journal of Chemical Theory and Computation,2010,6(3):880-889.
[26]Cheng J,Sulpizi M,Vande Vondele J,et al.Hole localization and thermochemistry of oxidative dehydrogenation of aqueous rutile Ti O2(110)[J].Chem Cat Chem,2012,4(5):636-640.
[27]Sun C H,Liu L M,Selloni A,et al.Titania-water interactions:A review of theoretical studies[J].Journal of Materials Chemistry,2010,20(46):10319-10334.
[28]He Y,Tilocca A,Dulub O,et al.Local ordering and electronic signatures of submonolayer water on anatase Ti O2(101)[J].Nature Materials,2009,8(7):585-589.
[29]Zhao W N,Liu Z P.Mechanism and active site of photocatalytic water splitting on titania in aqueous surroundings[J].Chemical Science,2014,5(6):2256-2264.
[30]Arrouvel C,Digne M,Breysse M,et al.Effects of morphology on surface hydroxyl concentration:A DFT comparison of anatase-Ti O2and gamma-alumina catalytic supports[J].Journal of Catalysis,2004,222(1):152-166.
[31]Sanchez V M,Sued M,Scherlis D A.First-principles molecular dynamics simulations at solid-liquid interfaces with a continuum solvent[J].Journal of Chemical Physics,2009,131(17):174108.
[32]Li Y F,Selloni A.Theoretical study of interfacial electron transfer from reduced anatase Ti O2(101)to adsorbed O2[J].Journal of the American Chemical Society,2013,135(24):9195-9199.
[33]He Y B,Dulub O,Cheng H Z,et al.Evidence for the predominance of subsurface defects on reduced anatase Ti O2(101)[J].Physical Review Letters,2009,102(10):106105.
[34]Hiemstra T,Venema P,Van Riemsdijk W H.Intrinsic proton affinity of reactive surface groups of metal(Hydr)oxides:The bond valence principle[J].Journal of Colloid and Interface Science,1996,184(2):680-692.
[35]Cheng J,Liu X,Vande Vondele J,et al.Redox potentials and acidity constants from density functional theory based molecular dynamics[J].Accounts of Chemical Research,2014,47(12):3522-3529.
[36]Cheng J,Liu X D,Kattirtzi J A,et al.Aligning electronic and protonic energy levels of proton-coupled electron transfer in water oxidation on aqueous Ti O2[J].Angewandte Chemie-International Edition,2014,53(45):12046-12050.
[37]Cheng J,Liu X D,Vande Vondele J,et al.Reductive hydrogenation of the aqueous rutile Ti O2(110)surface[J].Electrochimica Acta,2015,179:658-667.
[38]Cheng H Z,Selloni A.Hydroxide ions at the water/anatase Ti O2(101)interface:structure and electronic states from first principles molecular dynamics[J].Langmuir,2010,26(13):11518-11525.
[2]Xiong G,Shao R,Droubay T C,et al.Photoemission electron microscopy of Ti O2anatase films embedded with rutile nanocrystals[J].Advanced Functional Materials,2007,17(13):2133-2138.
[3]Kullgren J,Aradi B,Frauenheim T,et al.Resolving the controversy about the band alignment between rutile and anatase:The role of OH-/H+adsorption[J].Journal of Physical Chemistry C,2015,119(38):21952-21958.
[4]Sanches F F,Mallia G,Liborio L,et al.Hybrid exchange density functional study of vicinal anatase Ti O2surfaces[J].Physical Review B,2014,89(24):245309.
[5]Wang Y,Ma J,Zhou J P,et al.First-principles study of the electronic structure of nonmetal-doped anatase Ti O2[J].Journal of the Korean Physical Society,2016,68(3):409-414.
[6]Unal H,Gunceler D,Gulseren O,et al.Hybrid functional calculated optical and electronic structures of thin anatase Ti O2nanowires with organic dye adsorbates[J].Applied Surface Science,2015,354:437-442.
[7]Valentin C D,Selloni A.Bulk and surface polarons in photoexcited anatase Ti O2[J].The Journal of Physical Chemistry Letters,2011,2(17):2223-2228.
[8]Cheng J,Sprik M.Aligning electronic energy levels at the at the Ti O2/H2O interface[J].Physical Review B,2010,82(8):081406.
[9]Fujishima A,Honda K.Electrochemical Photolysis of water at a semiconductor electrode[J].Nature,1972,238(5358):37-38.
[10]Gong X Q,Selloni A,Vittadini A.Density functional theory study of formic acid adsorption on anatase Ti O2(001):Geometries,energetics,and effects of coverage,hydration,and reconstruction[J].Journal of Physical Chemistry B,2006,110(6):2804-2811.
[11]Wang Y,Zhang H M,Liu P R,et al.Engineering the band gap of bare titanium dioxide materials for visiblelight activity:A theoretical prediction[J].RSC Advances,2013,3(23):8777-8782.
[12]Mao X C,Lang X F,Wang Z Q,et al.Band-gap states of Ti O2(110):Major contribution from surface defects[J].Journal of Physical Chemistry Letters,2013,4(22):3839-3844.
[13]Rodriguez H F,Tranca D C,Szyja B M,et al.Water splitting on Ti O2-based electrochemical cells:A small cluster study[J].Journal of Physical Chemistry C,2016,120(1):437-449.
[14]Pan J,Liu G,Lu G Q,et al.On the true photoreactivity order of{001},{010},and{101}facets of anatase Ti O2crystals[J].Angewandte Chemie-International Edition,2011,50(9):2133-2137.
[15]Cheng J,Sulpizi M,Sprik M.Redox potentials and p Ka for benzoquinone from density functional theory based molecular dynamics[J].The Journal of Chemical Physics,2009,131(15):154504.
[16]Trasatti S.The absolute electrode potential:An explanatory note[J].Pure and Applied Chemistry,1986,58(7):955-966.
[17]Perdew J P,Burke K,Ernzerhof M.Generalized gradient approximation made simple[J].Physical Review Letters,1996,77(18):3865-3868.
[18]Ehrlich S,Moellmann J,Reckien W,et al.System-dependent dispersion coefficients for the DFT-D3 Treatment of adsorption processes on ionic surfaces[J].Chem Phys Chem,2011,12(17):3414-3420.
[19]Moellmann J,Ehrlich S,Tonner R,et al.A DFT-D study of structural and energetic properties of Ti O2modifica tions[J].Journal of Physics-Condensed Matter,2012,24(42):424206.
[20]The CP2K developers group.http://cp2k.berlios.de(accessed Feb 2010).
[21]Vande Vondel J,Krack M,Mohamed F,et al.QUICKSTEP:Fast and accurate density functional calculations using a mixed Gaussian and plane waves approach[J].Computer Physics Communications,2005,167(2):103-128.
[22]Goedecker S,Teter M,Hutter J.Separable dual-space gaussian pseudopotentials[J].Physical Review B,1996,54(3):1703-1710.
[23]Hartwigsen C,Goedecker S,Hutter J.Relativistic separable dual-space gaussian pseudopotentials from H to Rn[J].Physical Review B,1998,58(7):3641-3662.
[24]Vande Vondele J,Hutter J.Gaussian basis sets for accu rate calculations on molecular systems in gas and condensed phases[J].Journal of Chemical Physics,2007,127(11):114105.
[25]Cheng J,Sprik M.Acidity of the aqueous rutile Ti O2(110)surface from density functional theory based molecular dynamics[J].Journal of Chemical Theory and Computation,2010,6(3):880-889.
[26]Cheng J,Sulpizi M,Vande Vondele J,et al.Hole localization and thermochemistry of oxidative dehydrogenation of aqueous rutile Ti O2(110)[J].Chem Cat Chem,2012,4(5):636-640.
[27]Sun C H,Liu L M,Selloni A,et al.Titania-water interactions:A review of theoretical studies[J].Journal of Materials Chemistry,2010,20(46):10319-10334.
[28]He Y,Tilocca A,Dulub O,et al.Local ordering and electronic signatures of submonolayer water on anatase Ti O2(101)[J].Nature Materials,2009,8(7):585-589.
[29]Zhao W N,Liu Z P.Mechanism and active site of photocatalytic water splitting on titania in aqueous surroundings[J].Chemical Science,2014,5(6):2256-2264.
[30]Arrouvel C,Digne M,Breysse M,et al.Effects of morphology on surface hydroxyl concentration:A DFT comparison of anatase-Ti O2and gamma-alumina catalytic supports[J].Journal of Catalysis,2004,222(1):152-166.
[31]Sanchez V M,Sued M,Scherlis D A.First-principles molecular dynamics simulations at solid-liquid interfaces with a continuum solvent[J].Journal of Chemical Physics,2009,131(17):174108.
[32]Li Y F,Selloni A.Theoretical study of interfacial electron transfer from reduced anatase Ti O2(101)to adsorbed O2[J].Journal of the American Chemical Society,2013,135(24):9195-9199.
[33]He Y B,Dulub O,Cheng H Z,et al.Evidence for the predominance of subsurface defects on reduced anatase Ti O2(101)[J].Physical Review Letters,2009,102(10):106105.
[34]Hiemstra T,Venema P,Van Riemsdijk W H.Intrinsic proton affinity of reactive surface groups of metal(Hydr)oxides:The bond valence principle[J].Journal of Colloid and Interface Science,1996,184(2):680-692.
[35]Cheng J,Liu X,Vande Vondele J,et al.Redox potentials and acidity constants from density functional theory based molecular dynamics[J].Accounts of Chemical Research,2014,47(12):3522-3529.
[36]Cheng J,Liu X D,Kattirtzi J A,et al.Aligning electronic and protonic energy levels of proton-coupled electron transfer in water oxidation on aqueous Ti O2[J].Angewandte Chemie-International Edition,2014,53(45):12046-12050.
[37]Cheng J,Liu X D,Vande Vondele J,et al.Reductive hydrogenation of the aqueous rutile Ti O2(110)surface[J].Electrochimica Acta,2015,179:658-667.
[38]Cheng H Z,Selloni A.Hydroxide ions at the water/anatase Ti O2(101)interface:structure and electronic states from first principles molecular dynamics[J].Langmuir,2010,26(13):11518-11525.