影响光催化反应活性几种重要参数的理论研究

发布时间：2018-04-29 16:38

本文选题：光催化活性 + 反应温度　；参考：《南昌航空大学》2017年硕士论文

【摘要】：自从Fujishima和K.Honda在1972年发现在光照下TiO2可以将水裂解成氢气和氧气,光催化学科就此诞生。几十年来,经过一大批人的不懈努力,光催化研究取得了很大的突破。但是这些突破主要体现在光催化剂的材料合成、形貌表征、催化活性等,人们对光催化的理论研究寥寥无几。本文对光催化反应温度、光催化剂颗粒尺寸、光催化剂的介电常数和掺杂光催化剂价带能级简并消除等因素对光催化活性的影响做了理论研究,主要包括以下几个部分:1.光催化反应温度对光催化活性的影响研究。该部分在理论上分别从光催化反应温度对空穴和光电子数目的影响、光催化反应温度对空穴和光电子氧化还原被氧化还原分子效果的影响这两个方面进行研究,然后找出光催化反应活性与反应温度的关系。其中对于第二个方面,我们分别从光催化剂表面上的基团与被氧化还原分子相互吸引和相互排斥两种情况下对其进行研究。分别得到了当光催化剂表面基团和溶液中存在的被氧化还原分子相互排斥、相互吸引、相互排斥和相互吸引同时存在三种情况下光催化反应温度与光催化反应活性之间的关系。2.光催化剂颗粒尺寸对光催化活性的影响研究。该部分在理论上分别从光催化剂颗粒尺寸对光催化剂颗粒与被氧化还原分子的总接触面积的影响、光催化剂颗粒尺寸对被氧化还原分子在光催化剂颗粒表面的停留时间的影响和光催化剂颗粒尺寸对空穴和光电子氧化还原能力的影响对光催化剂颗粒尺寸和光催化活性的关系进行研究。从理论上解释了颗粒尺寸小的光催化剂催化活性好的原因。3.光催化剂的介电常数对光催化活性的影响研究。这是首次对光催化剂的介电常数与光催化活性的关系进行研究。该部分在理论上给出了描述光电子寿命与光催化剂的介电常数之间的关系方程,结合光催化反应机理,得出了介电常数大的光催化剂催化活性好的结论。4.掺杂光催化剂价带能级简并消除对光催化活性的影响研究。这是首次对掺杂光催化剂价带能级简并消除现象对光催化活性的影响进行研究。通过理论分析发现本征半导体光催化剂掺入杂质后会产生能级简并消除现象而导致能级简并度大大降低,进而导致价带上能够跃迁到导带的电子数大大减少,所以会造成尽管掺入杂质光催化剂的禁带宽度比本征半导体光催化剂窄,但由于本征半导体光催化剂价带上能够跃迁到导带的电子数远远大于掺杂质光催化剂而光催化活性比掺杂质光催化剂好的反常现象。
[Abstract]:Since Fujishima and K.Honda discovered in 1972 that TiO2 can break water into hydrogen and oxygen under light, photocatalysis was born. Over the past decades, photocatalytic research has made a great breakthrough through the unremitting efforts of a large number of people. However, these breakthroughs are mainly reflected in the synthesis of photocatalyst materials, morphology characterization, catalytic activity and so on. In this paper, the effects of photocatalytic reaction temperature, particle size, dielectric constant of photocatalyst and the degeneracy of valence band energy level of doped photocatalyst on photocatalytic activity are studied theoretically, including the following parts: 1. The effect of the temperature of photocatalytic reaction on photocatalytic activity was studied. In this part, the effects of the temperature of photocatalytic reaction on the number of holes and photoelectrons, and the effect of the temperature of photocatalytic reaction on the effect of redox molecules on hole and photoelectron redox were studied theoretically. Then the relationship between photocatalytic reaction activity and reaction temperature was found out. For the second aspect, we study the photocatalyst from the case that the groups on the surface of the photocatalyst and the redox molecules attract each other and mutually repel each other. The relationship between photocatalytic reaction temperature and photocatalytic activity was obtained when the surface group of photocatalyst and the redox molecules existed in the solution were repellent, attractive, mutually repulsive and mutually attractive at the same time. The effect of particle size of photocatalyst on photocatalytic activity was studied. In this part, the influence of the size of photocatalyst particle on the total contact area between the photocatalyst particle and the redox molecule is studied theoretically. Effect of particle size of photocatalyst on residence time of redox molecules on surface of photocatalyst and effect of particle size of photocatalyst on hole and photoelectron redox ability on particle size and photocatalytic activity of photocatalyst The relationship between chemical activity and chemical activity was studied. The reason why the photocatalyst with small particle size has good catalytic activity is explained theoretically. The effect of dielectric constant of photocatalyst on photocatalytic activity was studied. This is the first time to study the relationship between the dielectric constant and photocatalytic activity of photocatalyst. In this part, the equation describing the relationship between photoelectron lifetime and the dielectric constant of photocatalyst is given theoretically. Combined with the mechanism of photocatalytic reaction, the conclusion that the photocatalytic activity of photocatalyst with large dielectric constant is good is obtained. The effect of valence band energy level degeneracy on photocatalytic activity of doped photocatalyst was studied. This is the first time to study the effect of valence band energy level degeneracy elimination on photocatalytic activity of doped photocatalyst. Through theoretical analysis, it is found that the intrinsic semiconductor photocatalyst doped with impurity will produce degeneracy of energy level and eliminate the phenomenon of degeneracy of energy level, which leads to the decrease of degeneracy degree of energy level, which leads to the reduction of the number of electrons that the valence band can transfer to the conduction band. So even though the bandgap of the doped photocatalyst is narrower than that of the intrinsic semiconductor photocatalyst, However, the photocatalytic activity of the intrinsic semiconductor photocatalyst is better than that of the impurity photocatalyst due to the fact that the electron number of the intrinsic semiconductor photocatalyst can move to the conduction band is much larger than that of the impurity photocatalyst.
【学位授予单位】：南昌航空大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.3;O644.1

【相似文献】