Co,N共掺杂锐钛矿相TiO2电子结构和光学性质的第一性原理研究

二氧化钛（TiO₂）作为一种性能优良的光催化剂已经被广泛地研究和使用.本研究中利用了第一性原理和GGA+U方法,对锐钛矿结构TiO₂晶体三种可能的（Co,N）共掺杂体系的几何结构、形成能、电子结构和光吸收系数进行了研究,并与单掺杂（Co/N）体系进行了对比.结果表明,在三种共掺杂TiO₂中,Co与N相邻时晶格畸变最小,但掺杂原子周围晶格畸变较大;同时,较低的形成能表明此种共掺杂结构最容易形成;此外,因为C0与N成键,其杂质能级的数目与能量较其他共掺杂结构有较大差异.（Co,N）共掺杂体系与未掺杂TiO₂的相比,其禁带宽度较小,禁带中存在杂质能级,因此其吸收边红移,在可见光波段有较好的光吸收能力.故（Co,N）共掺杂可以很好地提升锐钛矿型TiO₂在可见光波段的光催化性能.

First Principle Calculations of the Electronic Structure and Optical Properties of (Co, N) Co-doped Anatase

Titanium dioxide (TiO2), as a kind of excellent photocatalyst, has been widely researched and applied. The geometry structure, electronic structure and absorption coefficient of three possible kinds of (Co, N) co-doped anatase were studied by the density functional theory (DFT) based on GGA+U method, and the results were compared with the single doped (Co/N) anatase. The result shows that the introduction of N dopant is the main factor which leads to the lattice distortion in (Co, N) co-doped anatase. And among the three co-doped anatase, the structure that Co and N are neighbor has the smallest lattice distortion overall and the greatest lattice distortion around the dopants; besides, the lower formation energy indicates that such co-doped structure is the most likely structure in (Co, N) co-doped anatase; in addition, because the existence of bond between Co and N, the number and energy of impurity levels in such structure is different from other co-doped structure. In addition, compared to undoped TiO2, (Co, N) co-doped TiO2 has smaller band gap and absorption edge, which is mainly derived from the impurity level in the gap. Therefore, (Co, N) co-doped anatase has good photocatalytic performance in visible light band.