Fully Exposed Metal Clusters: Fabrication and Application in Alkane Dehydrogenation

Alkanes are the foremost basic energy sources and represent an important basic chemical material for industrial applications. Highly efficient activation of C-H bonds can convert abundant alkanes into value-added products, such as alkenes and their corresponding polymers. Therefore, C-H bond activation of alkanes has attracted widespread attention in heterogeneous catalysis. Fully exposed cluster catalysts (FECCs), as a bridge linking metal single atoms (SAs) and nanoparticles (NPs), have been widely studied for many catalytic reactions, especially for alkane dehydrogenation. On FECCs, the highly exposed active sites with multiple metal atoms can promote adsorption of alkanes and intermediates, thus enabling facile C-H activation. Moreover, the electron-rich surface can facilitate the desorption of products to suppress overdehydrogenation and coke formation. Therefore, FECCs have exhibited remarkable catalytic performance in alkane dehydrogenation, compared with SAs and NPs. In this Review, we highlight the developments on FECCs, including the structure design and their unique catalytic performance in dehydrogenation of alkanes. The synthetic methods to fabricate FECCs are discussed for alkane dehydrogenation. Subsequently, recent progresses on understanding the relationship between catalytic performance and geometric/electronic structure of FECCs are summarized, to provide the insights into the nature of structure dependence and metal dependence in alkane dehydrogenation. The strategies to stabilize FECCs for alkane dehydrogenation, including support confining and bimetallic system construction, are systematically reviewed to provide a useful guidance for the catalyst design. Lastly, major prospects in FECCs are illustrated from the viewpoint of alkane dehydrogenation.