Peng Bo, Liu Yanyan, Aarts Dirk G A L, Dullens Roel P A
Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK.
Department of Applied Physics, Aalto University, Espoo FI-00076, Finland.
Soft Matter. 2021 Feb 19;17(6):1480-1486. doi: 10.1039/d0sm02100h.
Photo-catalytically active crystalline TiO2 has attracted special attention due to its relevance for renewable energy and is typically obtained by the calcination of amorphous TiO2. However, stabilising hollow colloidal TiO2 particles against aggregation during calcination without compromising their photocatalytic activity poses two conflicting demands: to be stable their surface needs to be coated, while efficient photocatalysis requires an exposed TiO2 surface. Here, this incompatibility is resolved by partially coating TiO2 shells with evenly distributed 3-trimethoxysilyl propyl methacrylate (TPM) lobes. These lobes act both as steric barriers and surface charge enhancers that efficiently stabilise the TiO2 shells against aggregation during calcination. The morphology of the TPM lobes and their coverage, and the associated particle stability during the calcination-induced TiO2 crystallization, can be controlled by the pH and the contact angle between TPM and TiO2. The crystal structure and the grain size of the coated TiO2 shells are controlled by varying the calcination temperature, which allows tuning their photocatalytic activity. Finally, the durable photocatalytic activity over many usage cycles of the coated TiO2 compared to uncoated shells is demonstrated in a simple way by measuring the photo-degradation of a fluorescent dye. Our approach offers a general strategy for stabilising colloidal materials, without compromising access to their active surfaces.
具有光催化活性的结晶TiO₂因其与可再生能源的相关性而备受关注，通常通过非晶TiO₂的煅烧获得。然而，在不影响其光催化活性的情况下，使空心胶体TiO₂颗粒在煅烧过程中稳定不聚集存在两个相互矛盾的要求：为了稳定，其表面需要被包覆，而高效的光催化需要TiO₂表面暴露。在此，通过用均匀分布的甲基丙烯酸3 - 三甲氧基硅丙酯（TPM）叶对TiO₂壳进行部分包覆来解决这种不相容性。这些叶既作为空间位阻屏障又作为表面电荷增强剂，在煅烧过程中有效地稳定TiO₂壳防止聚集。TPM叶的形态及其覆盖率，以及在煅烧诱导的TiO₂结晶过程中相关的颗粒稳定性，可以通过pH值以及TPM与TiO₂之间的接触角来控制。通过改变煅烧温度可以控制包覆的TiO₂壳的晶体结构和晶粒尺寸，这使得能够调节其光催化活性。最后，通过测量荧光染料的光降解，以一种简单的方式证明了与未包覆的壳相比，包覆的TiO₂在许多使用循环中具有持久的光催化活性。我们的方法提供了一种稳定胶体材料的通用策略，而不会影响其活性表面的可及性。
