Engineering the Coordination Sphere of Isolated Active Sites to Explore the Intrinsic Activity in Single-Atom Catalysts

Abstract

Reducing the dimensions of metallic nanoparticles to isolated, single atom has attracted considerable attention in heterogeneous catalysis, because it significantly improves atomic utilization and often leads to distinct catalytic performance. Through extensive research, it has been recognized that the local coordination environment of single atoms has an important influence on their electronic structures and catalytic behaviors. In this review, we summarize a series of representative systems of single-atom catalysts, discussing their preparation, characterization, and structure–property relationship, with an emphasis on the correlation between the coordination spheres of isolated reactive centers and their intrinsic catalytic activities. We also share our perspectives on the current challenges and future research promises in the development of single-atom catalysis. With this article, we aim to highlight the possibility of finely tuning the catalytic performances by engineering the coordination spheres of single-atom sites and provide new insights into the further development for this emerging research field.

Emerging Ultrahigh‐Density Single‐Atom Catalysts for Versatile Heterogeneous Catalysis Applications: Redefinition, Recent Progress, and Challenges

“…At present, due to the easy synthesis of ultrahigh-density SACs, it is possible to explore the synergy between adjacent active centers. [40][41][42] The space distance between two single atoms can be precisely controlled in 1-3 Å (10-20 atoms nm À2 ) using a variety of strategies (see Table 1), so it is helpful to promote the "adjacency effect" of highly dense metal atoms, by sharing coordinated N atoms [241] and establishing electron interactions. [252] This special coordinated and electronic structures can achieve the unique double-site molecular adsorption (i.e., bridging adsorption mode) and high-efficiency molecular activation in different catalytic reactions.…”

Surface Modification of 2D Photocatalysts for Solar Energy Conversion

“…Since the concept of single-atom catalysis was first reported by Zhang and coworkers in 2011, it has been a hot research topic in the field of catalysis. [151,152] Due to the strong interaction between the isolated atoms and the 2D carrier, the charge-transfer process becomes more accessible, and the carrier separation process is thus accelerated. [153] Zuo et al have applied the surfactantstabilization method to successfully fabricate isolated-Pt-atomdecorated MOF nanosheets with a Pt loading content of 12.0 wt%.…”

Synthesis of N‐Doped Highly Graphitic Carbon Urchin‐Like Hollow Structures Loaded with Single‐Ni Atoms towards Efficient CO2Electroreduction

“…With these design principles, significant efforts have been devoted to exploring diverse nanostructured metal‐containing electrocatalysts, e.g., metals, metal oxides, and single‐atom materials [4–10] . In recent years, single‐metal sites anchored N‐doped carbon (M‐NC) materials have emerged as appealing alternatives to traditional materials for electrochemical CO 2 reduction due to their intriguing features, such as the high atom utilization efficiency, exceptional electronic properties, and considerable catalytic performance [11–19] …”

“…[4][5][6][7][8][9][10] In recent years, single-metal sites anchored N-doped carbon (M-NC) materi-als have emerged as appealing alternatives to traditional materials for electrochemical CO 2 reduction due to their intriguing features, such as the high atom utilization efficiency, exceptional electronic properties, and considerable catalytic performance. [11][12][13][14][15][16][17][18][19] The catalytic performance of M-NC materials is highly dependent on the exposure of active sites and mass transfer property. [20,21] However, many M-NC catalysts suffer from limited active sites since a large fraction of metal sites is hosted in the dense carbon framework and thus inaccessible by the reactants and electrolytes.…”