SP~3杂化的气体分子在金红石相二氧化钛(110)面吸附规律与特性
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摘要
采用基于密度泛函理论(DFT)体系下的第一性原理平面波超软赝势方法,研究了sp3杂化气体分子H2O,NH3和CH4在金红石相Ti O2(110)表面的吸附.研究发现:含有氧空位的表面较无氧空位表面更容易吸附气体分子.影响吸附稳定性和吸附能的主要因素是分子的极化率,分子极化率越大,吸附越稳定.表面氧空位对分子负电荷中心的吸附是整个吸附的主要原因.通过差分电荷密度和电荷布居数分析来看,表面与吸附分子存在电荷转移,转移电子数目大小为:N>O>C,吸附方式为化学吸附,吸附稳定性为NH3>H2O>CH4.通过态密度、吸收谱和反射谱分析发现,表面氧空位缺陷使材料在费米能级附近出现了态密度峰值,极大地改变了材料的光学性质,占主导作用;而表面吸附H2O,NH3,CH4分子后对表面的光学性质影响相对较低,占辅助作用.O,N,C原子的电子在费米能级附近的态密度贡献为N>O>C,与转移电子数目顺序一致.相比氧空位表面,吸附CH4后对材料的光学性质影响不大,但吸附H2O和NH3后其吸收系数和反射率有所降低.这为进一步研究该材料的气敏传感特性提供了理论基础.
This paper studied rutile titanium dioxide(110) surface adsorption sp3 hybrid gas molecules such as H2 O, NH3 and CH4 by using the first-principles plane-wave ultrasoft pseudopotential method based on density functional theory(DFT). The results showed that: comparing to the surface without oxygen vacancy, the surface containing oxygen vacancy more easily adsorbed gas molecules. The main factor affecting the adsorption stability and adsorption energy is polarizability of molecular. The main adsorption reason is surface oxygen vacancies adsorbing the negative charged center. From analysis of the difference charge density and charge population, charge transfer exists in surface and molecular and the order of transfer number is N>O>C. The adsorption method is chemical adsorption and adsorption stability is NH3>H2O>CH4. From analysis of density of states, absorption spectrum and reflectance spectrum, surface oxygen vacancy defects caused a peak in density of states near the Fermi level, greatly changed the optical properties of the material, which played the dominant role, while after the surface adsorption H2 O, NH3 and CH4 molecules had less influence on surface optical properties, which played the auxiliary role. The electrons of O, N, C atoms contribution to density of states near the Fermi energy is N>O>C, which is the same order of the electron transfer number. Compared to the surface oxygen vacancies, there is little effect on the optical properties of materials after adsorption of CH4, and the absorption coefficient and reflectance decreased after adsorption of H2 O and NH3. This study provides the theoretical foundation for the further study of the characteristics of gas sensing materials.
This paper studied rutile titanium dioxide(110) surface adsorption sp3 hybrid gas molecules such as H2 O, NH3 and CH4 by using the first-principles plane-wave ultrasoft pseudopotential method based on density functional theory(DFT). The results showed that: comparing to the surface without oxygen vacancy, the surface containing oxygen vacancy more easily adsorbed gas molecules. The main factor affecting the adsorption stability and adsorption energy is polarizability of molecular. The main adsorption reason is surface oxygen vacancies adsorbing the negative charged center. From analysis of the difference charge density and charge population, charge transfer exists in surface and molecular and the order of transfer number is N>O>C. The adsorption method is chemical adsorption and adsorption stability is NH3>H2O>CH4. From analysis of density of states, absorption spectrum and reflectance spectrum, surface oxygen vacancy defects caused a peak in density of states near the Fermi level, greatly changed the optical properties of the material, which played the dominant role, while after the surface adsorption H2 O, NH3 and CH4 molecules had less influence on surface optical properties, which played the auxiliary role. The electrons of O, N, C atoms contribution to density of states near the Fermi energy is N>O>C, which is the same order of the electron transfer number. Compared to the surface oxygen vacancies, there is little effect on the optical properties of materials after adsorption of CH4, and the absorption coefficient and reflectance decreased after adsorption of H2 O and NH3. This study provides the theoretical foundation for the further study of the characteristics of gas sensing materials.
引文
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12 Zhu H Q,Feng Q.A study on microscopic mechanism and optical gas sensing material characteristics of rutile titanium dioxide(110)surface adsorption NH3 molecules(in Chinese).Acta Opt Sin,2014,34:1016002[朱洪强,冯庆.金红石相Ti O2(110)面对NH3吸附的微观机制和光学气敏特性研究.光学学报,2014,34:1016002]
13 Hong F,Xu W J,Ni Y H,et al.A First-principles study of water adsorption at step edge on rutile Ti O2(110)surface(in Chinese).Sci Sin Chim,2012,42:806–814[洪峰,徐文娟,倪宇恒,等.水在金红石型Ti O2(110)表面<001>阶梯边缘吸附的第一性原理研究.中国科学:化学,2012,42:806–814]
14 Pittman R M,Bell A T.Raman investigations of NH3 adsorption on Ti O2,Nb2O5,and Nb2O5/Ti O2.Catal Lett,1994,24:1–13
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16 Zhu H Q,Feng Q,Yue Y X,et al.Microscopic mechanism and characteristics of optical gas sensing material rutile titanium dioxide(110)surface adsorption H2S molecules(in Chinese).Chin J Lasers,2014,41:1206001[朱洪强,冯庆,岳远霞,等.金红石相Ti O2(110)面吸附H2S分子光学气敏效应的微观机制与特性.中国激光,2014,41:1206001]
17 Han Y,Liu C J,Ge Q F.Interaction of Pt clusters with the anatase Ti O2(101)surface:?A first principles study.J Phys Chem B,2006,110:7463–7472
2 Fujishima A,Honda K.Electrochemical photolysis of water at a semiconductor electrode.Nature,1972,238:37–38
3 Hoffmann M R,Martin S T,Choi W,et al.Environmental application of semiconductor photocatalysis.Chem Rev,1995,95:69–96
4 Chen X B,Liu L,Yu P Y,et al.Increasing solar absorption for photocatalysis with black hydrogenated titanium dioxide nanocrystals.Science,2011,331:746–750
5 Labat F,Baranek P,Adamo C.Structural and electronic properties of selected rutile and anatase Ti O2 surfaces:?An ab initio investigation.J Chem Theor Comput,2008,4:341–352
6 Elliott S D,Bates S P.Assignment of the(1×2)surface of rutile Ti O2(110)from first principles.Phys Rev B,2003,67:035421
7 Zhu H Q,Feng Q.Microscopic characteristics mechanism of optical gas sensing material rutile titanium dioxide(110)surface adsorption of CO molecules(in Chinese).Acta Phys Sin,2014,63:133101[朱洪强,冯庆.光学气敏材料金红石相二氧化钛(110)面吸附CO分子的微观特性机理研究.物理学报,2014,63:133101]
8 Xiao B,Feng J,Chen J C,et al.Study of rutile(110)surface STM image via ab initio simulation(in Chinese).Acta Phys Sin,2008,57:3769–3774[肖冰,冯晶,陈敬超,等.金红石型Ti O2(110)表面性质及STM形貌模拟.物理学报,2008,57:3769–3774]
9 Ding K N,Li J Q,Zhang Y F,et al.Density functional study on the relaxation structures and O2 adsorption of Ti O2(110)surfaces(in Chinese).Chin J Chem,2003,61:705–710[丁开宁,李俊篯,章永凡,等.Ti O2(110)面的弛豫结构及吸附O2的密度泛函研究.中国化学,2003,61:705–710]
10 Ashino M,Uchihashi T,Yokoyama K,et al.Atomic-scale structures on a non-stoichiometric Ti O2(110)surface studied by noncontact AFM.Appl Surf Sci,2000,157:212–217
11 Wu X Y,Selloni A,Nayak S.First principles study of CO oxidation on Ti O2(110):The role of surface oxygen vacancies.J Chem Phys,2004,120:4512–4516
12 Zhu H Q,Feng Q.A study on microscopic mechanism and optical gas sensing material characteristics of rutile titanium dioxide(110)surface adsorption NH3 molecules(in Chinese).Acta Opt Sin,2014,34:1016002[朱洪强,冯庆.金红石相Ti O2(110)面对NH3吸附的微观机制和光学气敏特性研究.光学学报,2014,34:1016002]
13 Hong F,Xu W J,Ni Y H,et al.A First-principles study of water adsorption at step edge on rutile Ti O2(110)surface(in Chinese).Sci Sin Chim,2012,42:806–814[洪峰,徐文娟,倪宇恒,等.水在金红石型Ti O2(110)表面<001>阶梯边缘吸附的第一性原理研究.中国科学:化学,2012,42:806–814]
14 Pittman R M,Bell A T.Raman investigations of NH3 adsorption on Ti O2,Nb2O5,and Nb2O5/Ti O2.Catal Lett,1994,24:1–13
15 Chang J G,Chen H T,Ju S P,et al.Adsorption and dissociation of NH3 on clean and hydroxylated Ti O2 rutile(110)surfaces:A computational study.J Comput Chem,2011,32:1101–1112
16 Zhu H Q,Feng Q,Yue Y X,et al.Microscopic mechanism and characteristics of optical gas sensing material rutile titanium dioxide(110)surface adsorption H2S molecules(in Chinese).Chin J Lasers,2014,41:1206001[朱洪强,冯庆,岳远霞,等.金红石相Ti O2(110)面吸附H2S分子光学气敏效应的微观机制与特性.中国激光,2014,41:1206001]
17 Han Y,Liu C J,Ge Q F.Interaction of Pt clusters with the anatase Ti O2(101)surface:?A first principles study.J Phys Chem B,2006,110:7463–7472