A Review on Particle Size Effect in Metal‐Catalyzed Heterogeneous Reactions

Size of metal nanoparticles (NPs) plays decisive roles in metal‐catalyzed heterogeneous reactions, due to the drastic variation of the geometric and electronic properties of metal NPs with size. Along with the development of controlled catalyst synthesis, tremendous efforts have been devoted to understanding the nature of the particle size effect. In particular, identification of the individual roles of size‐dependent geometric and electronic effects on metal‐catalyzed reactions is essential, but remains challenging since they are tightly hybridized together with particle size variation. In this review, we first discuss the fundamentals of the size‐dependent geometric and electronic properties of metal NPs and their crucial roles in catalysis in general. Then we summarize the previous representative studies of the particle size effect, metal‐by‐metal, in heterogeneous catalysis. We highlighted the extension of particle size effect to ultrafine cluster and single‐atom catalysts, the new frontiers in heterogeneous catalysis. In the followings, we further introduce the recent advances in disentangling the size‐dependent geometric and electronic effects and unveiling their individual contributions to catalysis. Finally, we discuss the challenges and perspectives of investigations on the size effect in metal catalysis for the future studies.