【摘要】 用延展X射线吸收精细结构(EXAFS)技术并结合密度泛函理论(DFT)研究了Zn(Ⅱ)在锐钛型TiO2表面上微观吸附结构。EXAFS结果表明,Zn(Ⅱ)在吸附时由自由水合状态下的Zn—O六配位八面体结构向四配位四面体结构转化,中心Zn原子的第二配位层存在两种不同的Zn—Ti距离(R1=0.371和R2=0.332nm).用DFT方法对四配位水合Zn离子在簇Ti2O11H14上进行优化后发现,四配位的Zn—O平均距离为0.200nm;外层Zn—Ti结合存在两种稳定的吸附模式:单角吸附模式和更加稳定的双角吸附模式,其Zn—Ti距离分别为0.369和0.335nm.EXAFS结果与DFT计算结果吻合,说明Zn(Ⅱ)在锐钛型TiO2表面上存在不同的亚稳平衡态吸附结构.更多还原

【Abstract】 Microscopic adsorption modes of Zn(Ⅱ)on anatase TiO2-water interface were studied using extended X-ray absorption fine structure(EXAFS)spectroscopy.Quantitative analysis of the EXAFS spectra showed that the microscopic structure of Zn(Ⅱ)on anatase TiO2 is four coordinate complex,and there are at least two types of bonding based on the average Ti_Zn distances in the second sphere.Two different geometry configurations of single-corner(SC)and double-corner(DC)for adsorption on the(101)surface cluster were calculated using DFT method.The Zn_Ti distances are 0.369 nm and 0.335 nm for the single-corner adsorption mode and double-corner adsorption mode,respectively.Therefore,the EXAFS fitting data,R1=0.371 nm,R2=0.332 nm,can be well distinguished for SC and DC mode respectively.The calculation results also showed that the optimized Zn_O average distance of Zn_O tetrahedron is about 0.200 nm,which agree with the EXAFS results.These show that Zn was adsorbed onto TiO2 surfaces in different metastable equilibrium state(MEA)under the same thermodynamic conditions.更多还原