基于异质结和异相结光催化剂的电荷转移过程的光谱表征研究

Photocatalysis shows to be potential solution for energy crisis and the environmental pollution problems. Water splitting with semiconductor-based photocatalysts is one of the most ideal routes for hydrogen production using solar energy. However, most of the photocatalysts show low activity since the limited charge separation and transfer efficiency. Spectroscopy,especially ultrafast spectroscopy is the very useful tool on the study of the carrier dynamics and photocatalysis mechanism. Recently, the high performance water-splitting photocatalysts based on the junction and p-n junction have been demonstrated to be an effective strategy for promoting charge separation. We have found that proper junctions formed in semiconductor-based photocatalysts could lead to enhanced activity in either hydrogen or oxygen half reactions. However, fabricating efficient junctions and the essential relation between the junction and the photocatalytic activity are far less well understood. In this research project, the roles of junctions, and their photocatalytic mechanism of photocatalysts based on the junction will be studied by using the time-resolved spectroscopy with different time resolutions from fs to ms. The charge carrier dynamics of junctions and the key process in photocatalysis will be identified. Finally,the photocatalytic reaction processes will be investigated in combination with in situ spectroscopy. This project will promote us to understand the effect of the junction on the photocatalytic process, and their photocatalytic mechanism,and will be helpful in designing new photocatalyst based on the junction with high photocatalytic activity.

太阳能光催化是解决当前能源和环境问题的重要途径。利用光谱技术尤其是超快光谱技术研究光催化机理中的电荷分离迁移动力学问题，对认识光催化过程、促进光催化科学发展具有重要意义。近年来通过构建异相结、异质结、p-n结等来提高光催化活性研究受到广泛关注，我组率先提出光催化中"异相结"概念，发现异相结有利于电子-空穴分离，促进光催化反应。但结对光催化剂设计的影响及其对载流子电荷分离迁移动力学的作用尚需进一步研究。本项目提出用原位光谱技术尤其是原位时间分辨光谱技术（时间分辨发光光谱、时间分辨红外和紫外可见吸收光谱），在fs、ns、ms等时间范围内对异相结/异质结催化剂的光催化过程，尤其光生电荷的分离和迁移动力学进行研究，认识结在光催化载流子动力学中的作用，以及结对光催化性能的影响因素，理解光催化机理。通过本研究工作，认识异相结、异质结对光催化性能影响的本质，为指导设计合成新型高效光催化剂提供理论依据。

太阳能光催化是解决当前能源和环境问题的重要途径。利用光谱技术尤其超快光谱技术研究光催化机理中的电荷分离迁移动力学问题，对认识光催化过程、促进光催化科学发展具有重要意义。本项目对异相结/异质结催化剂的光催化过程，尤其光生电荷的分离和迁移动力学进行研究，认识结在光催化载流子动力学中的作用，以及结对光催化性能的影响因素，理解光催化机理。.本项目采用原位傅里叶变换红外光谱对光催化分解水进行了机理方面的研究，深入地研究光催化分解水的机理。初步研究表明，金红石和锐钛矿在水吸附后再光照时，红外光谱有不同的变化。通过对红外峰的归属，对揭示这一过程有重要的作用。.在纯相和混相的立方gama-Ga2O3和单斜brta-Ga2O3上开展了光催化全分解水的研究。发现所有的Ga2O3光催化剂都可以计量地将水分解为氢气和氧气，然而，具有少量beta相的混相gama/beta-Ga2O3光催化剂却表现出最低的活性，这与已报道的具有少量beta相的混相alfa/beta-Ga2O3光催化剂表现出最高活性是截然相反的。在基于Ga2O3和TiO2粒子组装的光电极体系上研究了表面异相结对光电催化性能的影响。有利于光催化反应的表面异相结在光电催化上显示出负面的效应，这主要可归因于表面异相结对半导体粒子间电荷传输的重大影响。对于光催化和光电催化反应，表面异相结有利于光生载流子的分流。.利用稳态及时间分辨光致发光光谱，对CdS量子点粒径大小在CdS-钴肟分子间电荷转移中的作用进行了研究。发现小粒径量子点具有更长的光生载流子寿命，且量子点束缚态载流子寿命更长。对半导体量子点尺寸的合适调控可以促进光催化体系光生电荷的分离和转移，从而进一步提高光催化活性。.对半导体量子点-分子催化剂复合光催化产氢体系中分子催化剂在量子点表面的吸附模式，及不同吸附模式对相应光生载流子动力学的影响进行了研究。观察到了自由电子及捕获态电子的快速转移过程，研究了表面快速的空穴捕获过程对量子点光生电子和空穴转移动力学的影响。.发表论文17篇， 会议论文4篇，申请专利3件。