Increasing attention has been paid to single-atom catalysts (SACs) in heterogeneous catalysis because of their unique electronic properties, maximized atomic utilization efficiency, and potential to serve as a bridge between the heterogeneous and homogeneous catalysis. However, SACs can have limited advantages or even constrained applications for the reactions that require designated metallic states with multiple atoms or surface sites with metal–metal bonds. As a cross-dimensional extension to the concept of SACs, fully exposed cluster catalysts (FECCs) offer diverse surface sites formed by an ensemble of metal atoms, for the adsorption and transformation of reactants/intermediates. More importantly, FECCs have the advantage of maximized atom utilization efficiency. Thus, FECCs provide a novel platform to design effective and efficient catalysts for certain chemical processes. This outlook summarizes recent advances and proposes prospective research directions in the design of catalysts and characterizations of FECCs, together with potential challenges.

中文翻译：

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完全暴露的团簇催化剂（FECC）：朝着富集的表面位置和充分的原子利用效率

由于其独特的电子性能，最大化的原子利用效率以及在多相催化和均相催化之间架起桥梁的潜力，因此越来越多地关注多相催化中的单原子催化剂（SAC）。但是，对于要求具有多个原子的指定金属态或具有金属-金属键的表面位点的反应，SAC的优势有限，甚至受其限制。作为SAC概念的横向扩展，完全暴露的簇状催化剂（FECC）提供了由金属原子整体形成的多种表面部位，用于反应物/中间体的吸附和转化。更重要的是，FECC具有最大化原子利用效率的优势。因此，FECC提供了一个新颖的平台，可以为某些化学过程设计有效的催化剂。该展望总结了最近的进展，并提出了催化剂设计和FECC表征的前瞻性研究方向，以及潜在的挑战。