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光学气敏材料吸附气体分子后导致光学性质发生变化,运用这一原理来检测环境中的气体成分,称为光学气敏效应。采用基于密度泛函理论(DFT)体系下的第一性原理平面波超软赝势方法,研究了光学气敏材料金红石相TiO2(110)表面吸附H2S分子的微观特性,计算了TiO2(110)表面吸附能、电荷密度、态密度和光学性质的变化。结果表明,TiO2最稳定的表面是终止于二配位O原子的(110)面,只有含有氧空位的表面才能稳定吸附H2S,且氧空位比例越高,越有助于H2S吸附于表面;表面吸附H2S以水平吸附方式为主,在氧空位比例达到33%时,吸附能为0.7985eV;吸附的实质是表面氧空位具有氧化性,氧化了H2S分子。在可见光400~760nm范围内,存在氧空位的TiO2(110)表面吸附H2S后都可改善表面的光学性质。氧空位缺陷浓度越高,改善材料对可见光的吸收和反射能力越强,光学气敏响应能力越佳。
Optical gas-sensitive materials absorb gas molecules resulting in changes in optical properties, the use of this principle to detect the gas composition of the environment, known as the optical gas sensor effect. The microscopic characteristics of H2S molecules adsorbed on the surface of rutile TiO2 (110) were investigated by the first principle plane wave super soft pseudopotential method based on density functional theory (DFT). The surface of TiO2 (110) Adsorption energy, charge density, density of states and optical properties. The results show that the most stable surface of TiO2 is the (110) surface which terminates in the two-coordinated O atoms. Only the surface containing oxygen vacancies can stably adsorb H2S. The higher the oxygen vacancy ratio, the more it contributes to the adsorption of H2S on the surface. Adsorption of H2S is mainly horizontal adsorption. When the oxygen vacancy ratio reaches 33%, the adsorption energy is 0.7985eV. The essence of adsorption is that the surface oxygen vacancies are oxidized and oxidize H2S molecules. In the visible light range of 400 ~ 760nm, the presence of oxygen vacancies TiO2 (110) surface adsorption of H2S can improve the optical properties of the surface. The higher the concentration of oxygen vacancy defects, the better the material’s ability of absorbing and reflecting visible light, the better the optical gas-sensing ability.