SINGLE-ATOM CATALYSTS: RATIONAL DESIGN AND SYNTHESIS, CHARACTERIZATION, AND APPLICATIONS

Shichao Ding

doi:10.7273/000004452

Nanocatalysts have attracted great attention and played an important role in various chemical reactions due to their nanostructure properties and good activities. However, nanocatalysts still have limitations such as relatively low atom utilization, multiple active centers, and the high cost of noble metal-based nanocatalysts. It has always been in line with the development requirements to continuously reduce the cost and improve the catalytic activity of nanocatalysts. An important principle to increase the specific activity of each metal atom is to downsize metal particles and endow the metal with a low-coordinated environment. Hence, in order to enhance the activities of nanocatalysts, some strategies are needed to continuously downsize the catalyst from nano/subnano-level to single-atom level to maximize the utilization of atoms and expose more uniform active sites. In this dissertation, different methods are used to rationally design and synthesize various carbon-based catalysts with single Fe atom sites, which are named Fe-N-C single-atom catalysts (SACs). The Fe-N-C SACs with a one-dimension nanowire structure are synthesized using the zinc-atom assisted method. Various characterization methods are used to identify the isolated single Fe sites that exist in Fe-Nx form. Such active sites can mimic the structure of the natural enzyme’s active center and exhibit excellent enzyme-like activity for highly-sensitive sensing. Moreover, the proposed ion imprinting derived strategy can precisely control the coordination number of center Fe atom, thereby enhancing the catalytical performance of SACs. Combining with MnOx nanocrystal, the catalytical activity and stability of Fe-N-C SACs toward oxygen reduction reaction (ORR) can be further improved. Finally, the heteroatom Cl tuning method is used to modulate the electronic/geometric structures and coordination environment of the central metal atoms in Fe-N-C SACs, which significantly boosts catalytic activity, durability, and selectivity toward ORR in fuel cells. The synthesized catalysts in this work possess well-dispersed Fe-Nx based single-atom sites and exhibit excellent catalytic performance. The rational design of SACs in this dissertation provides different strategies to control single-atom active sites, and continue to enhance the catalytic activity, selectivity, and stability in various applications.

SINGLE-ATOM CATALYSTS: RATIONAL DESIGN AND SYNTHESIS, CHARACTERIZATION, AND APPLICATIONS

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