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- 2017
MgO、SnO2、TiO2表面氧空位性质对气体光学传感特性的影响
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Abstract:
光学气敏传感器是当今研究领域的一个热门方向。文章采用密度泛函理论(DFT)体系下广义梯度近似(GGA)第一性原理平面波超软赝势方法，分析和计算了光学气敏材料岩盐型MgO、金红石型SnO2和锐钛矿型TiO2表面氧空位的特性。以CO作为吸附分子进行微观机理研究，研究不同氧化物表面吸附气体分子的机理。对氧化物表面的几何结构、吸附能、态密度、差分电荷密度、电荷布居、电荷转移、光学性质等进行分析。研究发现:含有氧空位缺陷的MgO(001)、SnO2(110)和TiO2(101)能稳定的吸附CO分子，吸附后造成了材料光学性质的变化，可作为光学气敏传感材料。分析发现：氧空位氧化能力的大小是光学性质改变的核心原因。表面吸附CO分子后，发现SnO2(110)表面对分子的吸附能最大，分子与表面的吸附距离最短。通过差分电荷密度和电荷布居数发现，表面与CO分子间存在电荷转移，其转移电子数目大小为：SnO2(110)＞TiO2(101)＞MgO(001)，由此得出不同氧化物表面氧化性的大小为：SnO2(110)＞TiO2(101)＞MgO(001)；通过对比吸收谱和反射谱发现：吸附气体分子后SnO2(110)表面的光学性质变化最为明显，是一种较好的光学气敏传感材料。
Abstract: Optical gas sensor materials is a hot research field in recent years. Rock salt MgO, rutile SnO2 and anatase TiO2 surface were researched and calculated by the first-principles plane-wave ultrasoft pseudopotential method based on density functional theory(DFT). CO acted as an adsorbed molecule. The different oxide surfaces microcosmic properties such as the geometric structure, adsorption energy, density of states, electron density difference, charge population, charge transfer and optical properties were researched. The results showed CO can steadily absorb on MgO(001), SnO2(110) and TiO2(101) surfaces with oxygen vacancies. The analysis found that absorption led to optical properties change. Oxygen vacancy oxidizability was the important reason to optical properties change. Absorbed the CO molecule, SnO2(110) surface had the highest adsorption energy and the shortest distance. Through analysis charge density difference and charge population, it found that charge transfer occured between CO molecule and materials surface. The electron transfer number in different surfaces was as follows SnO2(110)＞TiO2(101)＞MgO(001). The oxidative of different surfaces were as follows, SnO2(110)＞TiO2(101)＞MgO(001). Comparing absorption spectra with reflection spectra, SnO2(110) surface optical properties changed the most obviously. It indicated that the SnO2 was a good optical gas sensor material.
