新型铋系半导体调控塑化剂太阳光催化降解路径的研究

Plasticizer as environmental endocrine disruptor is poisonous to human beings so that it is urgent to deal with this kind of pollutant. Since phthalic acid esters (PAEs) ammount to the most part of plasticizer, the fast degradation of PAEs is one of the most important research areas in environmental chemistry. From related publications, it can be seen that the degradation rate of PAEs by photocatalysis and the toxicity of the evolved intermediates during the photocatalysis are closely related to their degradation pathways, which is essentially relevant to the different oxidative species produced by different photocatalytic system. Moreover, the formation of different oxidative species can be allied to the electron structure and band gap of photocatalysts. Based on the easy control of electron structure and band gap of Bi series semiconductors by tuning the composition of the slabs between [Bi2O2]2+ sheets and the change of chemical composition of the sheets, we propose an new idea here for the fast mineralization of PAEs through the control of electron structure and band gap for this kind semiconductors to produce different kind of oxidative species, which can attack the different groups in PAEs and then lead to the different degradation pathways. In order to make the new idea come true, based on the work we have done before, we will theoretically design and experimentally synthesize new Bi series semiconductors for PAE degradation, and make the electron structure of the semiconductors tunable for the production of different kind of oxidative species. Moreover, the effective adsorption of PAEs onto the surface of the photocatalysts will be studied for the high degradation efficiency. Furthermore, the degradation pathways of phthalate di(2-ethylhexyl) phthalate (DEHP) under different photocatalytic systems with different Bi series semiconductors will be explored deeply. The relationship between the structure of new Bi series semiconductors and the degradation pathway of different PAEs will be investigated as well. Through the above study, we hope that the control of the degradation pathway of PAEs can be realized by the new Bi series semiconductors, which will result in the environmentally friendly degradation of different PAEs under solar light. We believe that the study resulted from this proposed project will provide theoretical base for the fast environmental degradation of this kind of environmental pollutants.

塑化剂作为环境内分泌干扰物因对人体存在有害作用而成为急需处理的污染物，其环境友好降解是环境化学的重要研究方向。该类污染物在降解过程中因光催化体系产生的氧化性物种不同，导致其降解中间产物的结构和毒性不同，而不同氧化性物种的产生又与光催化剂的电子和能带结构有关系。本申请项目在前期工作的基础上，提出通过层状铋系半导体结构的调控来光生不同种类的氧化性自由基、从而进攻塑化剂不同基团、控制其降解中间产物结构（降解路径）、并实现该类污染物无毒性、快速矿化的环境友好降解新思路。为此，我们将深入探索塑化剂在不同结构铋系半导体光催化体系中的降解路径及其界面吸附的影响，从理论和实验角度来研究新型铋系半导体材料的设计、制备和结构调控，诠释新型铋系半导体结构与塑化剂光催化降解路径的关系规律，实现该类半导体调控塑化剂光催化的降解路径，最终使不同结构塑化剂能够在太阳光下环境友好地降解，为该类污染物的治理提供理论依据。

利用太阳光来降解内分泌干扰物——塑化剂的关键是光催化剂，其中铋系半导体材料因其层状结构和带隙很容易被调控而具有较好的活性，但是相关材料暴露晶面、内部结构等因素对其活性的影响规律还不是非常清晰，有待于进一步探索。此外，由于能源危机，光催化和电催化材料在分解水制氢、还原CO2为燃料等方面的应用研究也成为国际热点，其中高效、廉价新型催化材料的研制是未来清洁能源利用的基础。鉴于上述背景，本项目所从事的相关研究工作包括：1）研究了Bi3O4Cl不同暴露晶面对该材料活性的影响规律，探索了不同暴露晶面BiOCl实现碳掺杂的规律，研究了碳均相掺杂Bi3O4Cl层状结构材料来调控其内部电场以增强该材料的分解水产氧性能，制备并研究了单层Bi12O17Cl2@单层MoS2复合纳米片光催化制氢的性能。研究发现不同暴露晶面的卤氧铋光催化材料确实具有不同的降解污染物活性，而且还会导致碳掺杂的不同类型——均相掺杂和表面掺杂，从而调控该类层状材料的内建电场，使光催化性能有很大区别，同时单层Bi12O17Cl2@单层MoS2复合纳米片因能调控光生电子和空穴的定向移动而使其光催化性能大幅度提高。2）以金属铜及其氧化物为基础，研究了Cu2O半导体光催化还原CO2为甲烷的活性及其性能的增强，提出了用碳包覆的简单方法来解决其稳定性问题；尝试了将Cu纳米线作为衬底沉积含有Ni、Co、Fe等金属的层状双金属氢氧化物（LDH）用于电催化分解水产氢。结果表明Cu2O具有光催化还原CO2为甲烷的活性，而且与TiO2复合之后活性更高，但是稳定性很差，在表面包覆几个纳米厚的碳层可使Cu2O光催化稳定性的大幅度提升，导致该材料还原CO2为甲烷的优势充分发挥；由于Cu纳米线作为衬底与沉积在其表面暴露边缘的NiFe、NiCo LDH纳米片形成的核壳包覆结构，导致该类催化电极电催化分解水具有优异的性能，特别是Cu纳米线@NiFe LDH纳米片复合电极能在大电流下(≥100 mA/cm2)获得世界上目前最低的过电池。上述研究结果发表在了Energy Environ. Sci.、Environ. Sci. Technol.等国际权威刊物上，将为新型高效光催化剂和电催化剂的制备及其在环境治理和能源转换方面的应用提供理论依据。