Department of Chemical and Biomolecular Engineering, Faculty of Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore.
Acc Chem Res. 2013 Feb 19;46(2):226-35. doi: 10.1021/ar3001662. Epub 2012 Dec 6.
Despite significant advancements in catalysis research, the prevailing catalyst technology remains largely an art rather than a science. Rapid development in the fields of nanotechnology and materials chemistry in the past few decades, however, provides us with a new capacity to re-examine existing catalyst design and processing methods. In recent years, "nanocatalysts" has become a term often used by the materials chemistry and catalysis community. It refers to heterogeneous catalysts at nanoscale dimensions. Similar to homogeneous catalysts, freestanding (unsupported) nanocatalysts are difficult to separate after use. Because of their small sizes, they are also likely to be cytotoxic and pose a threat to the environment and therefore may not be practical for industrial use. On the other hand, if they are supported on ordinary catalyst carriers, the nanocatalysts would then revert to act as conventional heterogeneous catalysts, since chemists have known active metal clusters or oxide particles in the nanoscale regime long before the nanotechnology era. To resolve this problem, we need new research directions and synthetic strategies. Important advancements in catalysis research now allow chemists to prepare catalytic materials with greater precision. By controlling particle composition, structure, shape, and dimension, researchers can move into the next phase of catalyst development if they can bridge these old and new technologies. In this regard, one way seems to be to integrate active nanostructured catalysts with boundary-defined catalyst supports that are "not-so-nano" in dimension. However, these supports still have available hierarchical pores and cavity spaces. In principle, these devices keep the essence of traditional "catalyst-plus-support" type systems. They also have the advantages of nanoscale engineering, which involves both high level design and integration processes in their fabrication. Besides this, the active components in these devices are small and are easy to integrate into other systems. For these reasons, we refer to the final catalytic devices as integrated nanocatalysts (INCs). In this Account, we describe the current status of nanocatalyst research and introduce the various possible forms of design and types of integration for INC fabrication with increasing compositional and structural complexities. In addition, we discuss present difficulties and urgent issues of this research and propose the integration of the INCs into even more complex "supracatalysts" for future research.
尽管催化研究取得了重大进展，但主流的催化剂技术在很大程度上仍然是一门艺术而非科学。然而，过去几十年纳米技术和材料化学领域的快速发展为我们重新审视现有的催化剂设计和处理方法提供了新的能力。近年来，“纳米催化剂”一词已成为材料化学和催化界常用的术语。它是指纳米尺度的多相催化剂。与均相催化剂类似，独立（无载体）纳米催化剂在使用后难以分离。由于其尺寸较小，它们也可能具有细胞毒性，对环境构成威胁，因此可能不适用于工业用途。另一方面，如果将它们负载在普通催化剂载体上，纳米催化剂将恢复为常规多相催化剂，因为化学家在纳米技术时代之前很久就已经知道纳米尺度上的活性金属簇或氧化物颗粒。为了解决这个问题，我们需要新的研究方向和合成策略。现在，催化研究的重要进展使化学家能够更精确地制备催化材料。通过控制颗粒的组成、结构、形状和尺寸，如果研究人员能够将这些新旧技术结合起来，他们就可以进入催化剂开发的下一阶段。在这方面，一种方法似乎是将活性纳米结构催化剂与尺寸“非纳米”的边界限定催化剂载体集成。然而，这些载体仍然具有可用的分级孔和腔空间。原则上，这些装置保留了传统“催化剂加载体”型系统的本质。它们还具有纳米级工程的优点，包括在制造过程中的高级设计和集成。除此之外，这些装置中的活性组件很小，并且易于集成到其他系统中。因此，我们将最终的催化装置称为集成纳米催化剂（INC）。在本报告中，我们描述了纳米催化剂研究的现状，并介绍了随着组成和结构复杂性的增加，用于 INC 制造的各种可能的设计形式和集成类型。此外，我们讨论了这项研究目前的困难和紧迫问题，并提出了将 INCs 集成到更复杂的“超催化剂”中以进行未来研究的建议。
