Emerging Supported Metal Atomic Clusters for Electrocatalytic Renewable Conversions

Subnanometric supported metal atomic clusters (SMACs) composed of several to tens of surface metal atoms have attracted increased research interest in electrocatalysis. SMACs have been known to show distinct properties compared to their metal nanoparticles and single atom counterparts and have long been developed for functional improvements. Tremendous advancements have been made in the past few years, with a notable trend of more precise design down to an atomic/molecular level and the investigation transferring into more practical devices, which motivates this timely review. To begin, this review presents and classifies the classic and latest synthetic strategies and state-of-the-art characterization techniques of SMACs. It then outlines and discusses the basic structure design principles of SMACs, highlighting the importance of the organic ligands, size effect of the clusters, and support-cluster interactions in determining the catalytic activity and practical device stability. Thereafter, recent advances in several typical electrocatalysis processes from the laboratory scale to industrial scale are discussed to obtain a general understanding of the structure-activity correlations of SMACs. Current challenges and future perspectives in this emerging field are also discussed, aiming at practicing SMAC catalysts in future energy conversion devices.