中文摘要：

建立三个Cr掺杂TiO_2模型并计算了其电子结构。根据这些模型得到了相似的计算结果：掺杂Cr在TiO_2的禁带中引入带宽约为1.0 eV的中间能级,使其具有可见光响应特性。但是过多的Cr会成为光生电子-空穴对的复合中心,使掺杂TiO_2的光催化性能下降。在此基础上采用水热法制备了具有不同名义Cr掺杂浓度的纳米TiO_2粉体。结果表明,所制备的Cr掺杂纳米TiO_2均为锐钛矿型,比表面积为178-221 m~2/g,平均粒径为9 nm左右且粒径分布范围窄。Cr原子替代Ti原子进入了TiO_2晶格,不同名义Cr掺杂浓度样品均出现了对可见光的吸收。当原料中的Cr/Ti原子比为2%时Cr掺杂纳米TiO_2粉体具有最好的光催化性能,验证了理论计算结果。

英文摘要：

The Cr-doped TiO_2 models were established and the band structures have also been calculated.The similar result is obtained according to the three models：Cr-doping gives intermediate energy of about 1.0eV in the band gap,which means it can shift the absorption edge of TiO_2 to visible region.But too much Cr-doping can also result in recombination center of electron-hole and a decline in photocatalytic activity.Nanocrystalline Cr-doped TiO_2 powders with different initial Cr/Ti ratio in starting materials have been prepared by hydrothermal method.The results show that the prepared powders are all composed of anatase TiO_2,the BET specific surface area of the powders are ranged form 178 to 221 m~2/g,the averaged grain size is about 9 nm and the size distribution is narrow.Cr~（3＋） has been doped into the lattice of TiO_2 instead of Ti.All the absorption edges of Cr-doped TiO_2 powders with different nominal doping concentration of Cr~（3＋） have been red-shifted into visible light region.In our case,Cr-doped TiO_2 with initial Cr/Ti atomic ratio of 2%in starting materials has the best photocata lytic activities when decompose the MB in its aqueous solution,which is consistent with that of the theoretical results.