(292g) Supported Single Atom Catalyst Design, Synthesis, and Characterization Via Chelate Fixation Method

Single atom catalysts (SACs) have gained significant attention due to their distinctive performances for a wide variety of chemical reactions. These exceptional properties originate from intimate electronic interactions between the well-defined isolated active metal centers/sites and the support surface that facilitate spillover of adsorbed species onto the isolated single metal atoms. Various SACs have been developed in the literature that resulted in different populations of atomic species; however, their synthesis usually requires functional groups or defects on the surface on supports such as nitrogen-dopped carbon and ceria.

The current work describes a new, simple, general method called Chelate Fixation (CheFi), the schematic of which is shown in Figure 1-a, in which the need for support functional groups or defect sites is eliminated. In this method, we add a high-boiling chelating agent immediately after the incipient wetness impregnation of a metal precursor which chelates the precursors and anchors them to the support surface as the metal is reduced. Only subsequently is the chelating agent removed, allowing formation of stable, isolated metal species. In this way SACs can be synthesized over non-functional diamond carbon powder and unreducible oxides such as silica and alumina.

We demonstrate the method by synthesizing Pt single atoms isolated on MgO, TiO₂ and γ-Al₂O₃ supports. Representative STEM images of 0.77% Pt/MgO, 1.8% Pt/TiO₂ and 0.84% Pt/γ-Al₂O₃ samples are shown in Figure 1-b. Details of the synthesis and further work to understand the mechanism of chelate fixation will be discussed.