Understanding electronic and optical properties of anatase TiO2 photocatalysts co-doped with nitrogen and transition metals.
Understanding electronic and optical properties of anatase TiO2 photocatalysts co-doped with nitrogen and transition metals.
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DOI：
10.1039/c3cp51476e
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发表时间：
2013-05
期刊：
影响因子：
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通讯作者：
Q. Meng;Tuo Wang;E. Liu;Xinbin Ma;Q. Ge;Jinlong Gong
中科院分区：
文献类型：
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作者：
Q. Meng;Tuo Wang;E. Liu;Xinbin Ma;Q. Ge;Jinlong Gong
采用第一性原理密度泛函理论研究了过渡金属和氮共掺杂的TiO 2光催化剂的电子性质。已经考虑了十四种不同的过渡金属（M），包括Sc、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Y、Zr、Nb、Mo和Cd。提出了过渡金属系列共掺杂体系的特征能带结构。我们的研究结果表明，二氧化钛的吸收边转移到可见光区引入掺杂剂后，由于减少导带底（CBM）和杂质能级（IELS）的形成在带隙中。这些IEL主要由（a）M-O（M表示掺杂的过渡金属）键的反键轨道、（B）掺杂的过渡金属的不饱和非键d轨道（主要是d（xy）、d（yz）和d（xz））和（c）掺杂的过渡金属旁边的键的Ti-O键/Ti-N反键轨道形成。当掺杂金属的d价电子数在3 ~ 7之间时，（M，N）共掺杂体系的带隙中都出现了三种类型的IEL。对于掺杂有多于7个价电子的金属的系统，仅观察到（a）和（c）类型的IEL以及N的未被占据的pz态。基于我们的分析，我们提出，共掺杂系统，如（V，N），（Cr，N），和（Mn，N），其中具有显着的带宽IEL，是巨大的潜力，作为候选人的光伏应用在可见光范围内。
This paper describes an investigation into the general trend in electronic properties of anatase TiO2 photocatalysts co-doped with transition metals and nitrogen employing first-principles density functional theory. Fourteen different transition metals (M), including Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, and Cd, have been considered. The characteristic band structures of the co-doping systems involving the transition metal series are presented. Our results indicate that the absorption edges of TiO2 are shifted to the visible-light region upon introduction of dopants, due to the reduced conduction band minimum (CBM) and the formation of impurity energy levels (IELs) in the band gap. These IELs are primarily formed from (a) the anti-bonding orbitals of the M-O (M indicates the doped transition metal) bonds, (b) the unsaturated nonbonding d orbitals of the doped transition metal (mainly d(xy), d(yz), and d(xz)), and (c) the Ti-O bonding/Ti-N anti-bonding orbitals of the bond next to the doped transition metal. When the valence d electrons of the doped metal are between 3 and 7, all three types of IELs appear in the band gap of the (M, N) co-doped systems. For systems doped with a metal of more than 7 valence electrons, only types (a) and (c) of IELs as well as the unoccupied pz state of N are observed. Based on our analysis, we propose that the co-doping systems such as (V, N), (Cr, N), and (Mn, N), which have the IELs with a significant bandwidth, are of great potential as candidates for photovoltaic applications in the visible light range.