Catalysis Synergism by Atomically Precise Bimetallic Nanoclusters Doped with Heteroatoms.

Abstract

ConspectusBimetallic catalysts hold promise in tailoring the catalytic activity and selectivity of transition metals for important chemical processes due to the synergistic coupling between the constituent elements that can connect catalytical active sites. However, it remains a challenge to construct an ideal bimetallic catalyst to study the respective or cooperative effects of the two transition metals within the bimetallic catalyst on the overall catalytic performance because multiple factors are always convoluted, such as the size dispersity of particles, the inhomogeneous structure, and the unknown exact location of the two metal elements in any particle. Therefore, almost all of the current studies give rise to the statistics of the overall catalytic performance from all of the particles in a bimetallic catalyst or at least the observed performance reflects an ensemble average of all metal atoms in a particle. Atomically precise metal nanoclusters have attracted catalysis scientists since their total structures (core plus surface) were solved by single-crystal X-ray crystallography, thereby providing unparalleled opportunities to build a precise correlation of catalyst structures with catalytic properties at an atomic level. Within this field, we are interested in identifying catalytically active sites and further constructing the active sites by an atom-by-atom manipulation, which are typically challenging for conventional particle-based heterogeneous catalysts and organometallics-based complex catalysts.In this Account, we mainly focus on the extensive efforts to fundamentally understand catalysis synergy in bimetallic nanocluster catalysts doped with heterometallic atoms. We first briefly describe the design rules and chemical synthesis of atomically precise bimetallic nanoclusters doped with heteroatoms including co-reduction, atom substitution, and reconstruction as typical synthesis strategies. We then put particular emphasis on the recent research toward the synergistic effects of surface/subsurface heteroatoms of the bimetallic nanoclusters on controlling the catalytic pathways, in which a series of examples showed that catalytically active sites can be dramatically tailored by the metal heteroatoms (Ru, Cu, Ni, Cd, etc.) located on the surface or subsurface of gold nanoclusters. Other cases indicated that the catalytic activity can be driven by surface heteroatom-ligand motifs of bimetallic nanoclusters. We also discuss the remote effects of nonsurface or kernel heteroatoms located in the cores of bimetallic nanoclusters on improving the catalytic reactions directly occurring on the catalyst surface. Finally, we anticipate that the advances in this research field would not only provide in-depth insight into the intraparticle synergism in bimetallic catalysts for understanding and controlling their catalytic reactivity but also provide valuable guidelines for high-performance catalysts that can be applied in industry.