摘要/Abstract

半导体光生电荷分离是光催化过程中的关键步骤之一，其效率极大地影响了最终光催化性能.将TiO₂纳米片与石墨烯复合，能够促进TiO₂中光生电子和空穴的分离，从而提高其光催化活性.为了研究光生电荷的分离对TiO₂/石墨烯复合材料光催化性能的影响，通过调控TiO₂纳米片的尺寸来调节TiO₂/石墨烯复合材料中光生电荷分离的能力，然后研究其对TiO₂/石墨烯复合材料光催化性能的影响.合成了一系列不同厚度的TiO₂纳米片，将其与石墨烯复合，并通过光沉积负载Pt纳米颗粒作为助催化剂，用于光催化产氢.实验结果显示，随着TiO₂纳米片厚度减小，其与石墨烯形成的复合结构的光催化性能显著提高.这主要是由于TiO₂纳米片厚度减小时，光生电子沿厚度方向穿过TiO₂纳米片迁移到石墨烯的距离缩短，从而减少了光生电子在迁移过程中与空穴的复合；同时TiO₂纳米片厚度减小使其比表面积增大，使得TiO₂/石墨烯界面面积增大，从而使石墨烯更好地分离出TiO₂中的光生电子，有更多的光生电子到达石墨烯参与催化反应，提高TiO₂/石墨烯复合材料的光催化性能.此研究表明通过控制TiO₂纳米片的尺寸来调控TiO₂/石墨烯复合材料中光生电子和空穴的分离，是显著提高其光催化性能的有效途径.
关键词: TiO₂纳米片/石墨烯, 光生电荷分离, 纳米片尺寸, 电子迁移, 界面
Separation of photogenerated charges is one of the key steps in photocatalysis, whose efficiency largely determines the overall photocatalytic performance in water splitting. It is known that the formation of hybrid nanostructures is a promising solution to improve photocatalytic performance. However, the chemical environment difference during the synthesis of hybrid nanostructures may bring additional influencing factors to material systems. In this case, the design and synthesis of well-defined and clean samples are highly important to fundamental investigations. Integrating TiO₂ nanosheets with graphene can enhance the photocatalytic activity of TiO₂ through the effective separation of the photogenerated electrons and holes across the interface formed by C-O bonds. To investigate the influence of photogenerated charge separation on the photocatalytic performance of TiO₂/graphene composites, we modulate the separation of the photogenerated charges by controlling the size and thickness of TiO₂ nanosheets with the same chemical environment, which helps investigate its effect on the photocatalytic performance of TiO₂/graphene composites. Specifically, a series of TiO₂ nanosheets with different thickness are synthesized by controlling the amount of hydrofluoric acid and combined with graphene for photocatalytic hydrogen production. The hybrid nanostructures are formed through a simple and clean process so as to possess a reliable platform for evaluating the relationship between structural parameters and performance in photocatalytic hydrogen production. The experiment results show that the photocatalytic activity of TiO₂/rGO composites increases with the reduction in the thickness of TiO₂ nanosheets. As the thickness of TiO₂ nanosheets decreases, the migration distance of the photo-excited electrons is reduced so as to effectively suppress the recombination of the photo-excited charges. In the meanwhile, the TiO₂/graphene interface is enlarged to promote the separation of the photogenerated charges in TiO₂. As a result, the utilization efficiency of the photogenerated charges has been substantially enhanced. This work demonstrates that modulating the separation of photogenerated charges in TiO₂/graphene composites by controlling the size of TiO₂ nanosheets is an effective strategy for improving the photocatalytic performance of TiO₂/graphene composites.
Key words: TiO₂ nanosheet/graphene, photogenerated charge separation, nanosheet size, electron migration, interface


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