掺碳、氮二氧化钛多孔块体光生载流子寿命延长新机理探索

The recoverable titanium dioxide based photocatalysts could be used commercially only after its quantum efficiency has been upgraded to the commercially-required level. The recoverable titanium dioxide based photocatalysts mainly have two types: titanium dioxide based bulk and “titanium dioxide based film/bulk carrier”, both of which presently have high cost and low quantum photocatalytic efficiency. To solve the high cost problem, a microwave method would be employed to prepare the porous carbon-and-nitrogen co-doped titanium dioxide bulk and porous“carbon-and-nitrogen co-doped titanium dioxide film/metal bulk carrier” (hereafter called “film/plate”) in this proposal. This method is characteristic of low-cost, simplicity, and ability to apply in industry scale. More importantly, this method had been checked in our earlier-stage work to be successful in producing pores in bulk and depositing carbon-and-nitrogen co-doped titanium dioxide film on a bulk carrier. On the other hand, the low quantum efficiency arises mainly from short carriers’ lifetime. The applicants think that a macroscopic electric filed is more advantageous than a local internal electrical field in longer carriers’ lifetime. Therefore, in this work, on the above-said prepared samples, the following new mechanism which prolong the lifetime of photo-produced electrons and holes will be explored: (1) by producing a temperature step in the either ends of carbon-and-nitrogen co-doped titanium dioxide porous bulk, a macroscopic electric filed would be produced owing to the Seebeck effect; (2) by producing different bulk edge curvature radii, an inhomogeneous charge distribution in the carbon-and-nitrogen co-doped titanium dioxide porous bulk, therefore, a macroscopic electric field would occur; (3) by depositing porous carbon-and-nitrogen co-doped titanium dioxide film on the metal plate which has suitable work function resulting in producing a “hindering layer” in the “porous film/plate” , a unanimously direction of electric field perpendicular to the metal plane would be occur. This kind of electric field would separate the photo-produced holes and electrons in more amount. Therefore, a longer photo-produced carriers’ lifetime would be obtained.

光催化量子效率的提高是解决可回收二氧化钛（TiO2）基光催化材料商业应用瓶颈的途径。可回收TiO2基光催化材料主要有块体和“TiO2基/负载”两种形式。但目前这些材料成本高，光催化量子效率低。针对成本问题，本项目拟采用已在前期中取得成功的成本低、工艺简单、可工业化生产的微波法来制备碳、氮掺杂TiO2多孔块体和“碳、氮掺杂多孔TiO2薄膜/金属板”复合材料。而由于光催化量子效率低的主要原因是光生载流子寿命短。申请者提出采用宏观电场取代局域内建场来分离光生电子与空穴，更大幅度提高光生载流子寿命。故本项目探索以下延长光生载流子寿命新机理：（1）通过半导体Seebeck效应产生宏观电荷分离，自发建立宏观电场；（2）块体边缘曲率半径不同造成载流子分布不匀来自发建立宏观电场；（3）选择有合适功函数的金属板作为沉积碳、氮掺杂多孔TiO2薄膜基板，在膜和板之间建立方向一致阻挡层，延长光生载流子寿命。

光催化材料的应用依赖于该应用的成本和高量子效率。块体光催化材料可回收多次循环使用，降低成本，但其量子效率低。故本项目的初衷是通过提高块体光催化材料的量子效率来排除光催化材料应用的障碍。.提高光催化材料量子效率的主要途径是阻碍光生电子-空穴对的复合，延长其载流子寿命。本项目的主要通过在光催化棒两端加温差，产生宏观电场，进而对光催化棒内所有的光生电子-空穴进行有序分离，达到最大的光生载流子寿命，即最大的光催化量子效率。实验表明：温差能提高5.5倍的量子效率。本项目为光催化应用提供了宝贵的技术路径。.在本项目中设计通过调整杂质含量、块体形状、光能流密度来优化碳、氮掺杂二氧化钛的光催化性能。.本项目原计划通过半导体/金属结异质结获得块体材料的高量子效率，但该设计不如新近发展的方法，故放弃该路线，发展新的方法。本项目发展了大量的新方法：1O改进了Z模式的内涵。 2O利用非等价离子取代基相中离子制造氧缺位，用氧缺位吸附光生电子，使光生电子与空穴分离，增加其寿命。这些方法为提高光催化量子效率提供有效的途径。.本项目执行过程中超出最初的研究内容还发展了砖头上沉积碳、氮掺杂二氧化钛块体光催化剂、碳、氮掺杂二氧化钛复合活性碳等块体光催化剂。都获得较好的光催化性能。我们还在本项目研究内容之外额外研发了物理吸附四环素的方法。用可回收的Fe3O4在20分钟之内能全部吸附完四环素，用碱可以恢复Fe3O4的性能重复使用。这些额外做的内容的效果远远超过本项目的研究目标。Fe3O4吸附四环素完全可以应用了。.本项目原目标是发表 6 篇 SCI 文章，申请 2 件专利；计划参加 1 次光催化方面的国际会议，进行 1 次国际合作交流。本项目执行过程中发表SCI论文18篇，申请专利9件，专利授权6件。参加了3次国内学术会议，1次国际会，与美国Tetra Tech, Inc公司进行国际合作交流。远超过成果任务书的目标。