过渡金属Cu、Cr掺杂TiO2表面氧化性气体NO2光学气敏传感特性

采用密度泛函理论（DFT）体系广义梯度近似（GGA）第一性原理平面波超软赝势方法，分析锐钛矿型TiO₂（101）表面吸附NO₂分子光学气敏传感的微观机理.结果表明：Cu和Cr原子易于掺入TiO₂（101）表面，掺杂表面能稳定地吸附NO₂分子且吸附后光学性质发生显著变化.表面吸附NO₂分子后，Cu掺杂TiO₂（101）表面对分子的吸附能最大，吸附后结构更稳定，分子与表面的距离最短.通过分析差分电荷密度和电荷布居数发现，NO₂分子与基底表面间发生电荷转移，转移电子数目：Cu掺杂表面 > Cr掺杂表面 > 无掺杂表面.对比吸收光谱和反射光谱发现，在Cu掺杂表面吸附分子后，光学性质变化最明显，说明表面与吸附分子间氧化还原能力是决定光学气敏传感性能的核心因素.在过渡金属中，Cu与Cr都有4s价电子结构，其4s电子降低了材料表面氧空位的氧化性，增加了其还原性.对于氧化性气体，可以提升表面与分子的氧化还原作用，而Cu的4s电子更加活泼，从而光学气敏传感特性更加明显.因此，Cu掺杂的TiO₂对氧化性气体是一种较好的光学气敏传感材料.

Oxidizing Gas NO2 Optical Gas Sensing Characteristics of Transition Metal Cu and Cr Doped TiO2 Surfaces

With first-principles plane-wave ultrasoft pseudopotential method based on density functional(DFT) system, we analyze properties of optical gas sensor materials anatase TiO₂(101) surfaces with NO₂ adsorption. Cu and Cr atoms are easily doped on TiO₂(101) surface. Cu and Cr doped TiO₂(101) surfaces could absorbed NO₂ molecules steadily. After adsorption, material optical properties changed obviously. Cu doped TiO₂(101) surfaces have the highest adsorption energy and the shortest distance between surface and molecule. Analyzing charge density difference and charge population we found that charge transfer occurs between NO₂ molecule and material surface. Electron transfer number is as follows:Cu-doped surface > Cr-doped surface > Undoped surface. Comparing absorption and reflection spectra we found that Cu-doped surface optical properties changed obviously. Redox capacity between surfaces and molecules decided optical gas sensing propertiess. Cu and Cr has 4s valence electron structure which could reduce materials oxygen vacancies oxidative properties. For oxidizing gases, 4s electron could increase surfaces and molecules redox effect. Cu 4s electron is more active. It indicates that Cu doped TiO₂ is a good optical gas sensor material for oxidizing gases.