Date of Award

Fall 2021

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

First Advisor

Christopher T. Williams

Second Advisor

John R. Regalbuto

Abstract

Atomically distributed metal centers with maximized atom utilization efficiency called single-atom catalysts (SACs) have attracted significant attention in catalysis. SACs with the advantages of both homogeneous and heterogeneous catalysts have been rising as a new frontier in the field of catalysis. New catalytic technologies are ever-growing, considering 90% of all chemical processes employ catalysts, securing modern society’s sustainable future. A classical field in catalysis has been dedicated to catalysis by supported metals. Recently, a vast effort has been devoted to smaller catalyst particles where size is restricted to a single atom on a surface. Single atoms supported or embedded on the surface of solid support involving covalent, coordination, or ionic bonds help rationalize the structure and the reactivity.

Heterogeneous single-atom catalysts have tremendous potential, but a facile synthesis at high metal loadings remains a challenge. Herein, we present two simple, scalable methods for doing so, applicable to a wide variety of metals and carbon and oxide supports. The methods of “switched solvent synthesis” (SwiSS) and “chelate fixation” (CheFi) prevent precursor agglomeration during drying and reduction caused by the presence of water. A non-soluble chelating agent dissolved in a polar solvent with a higher dipole moment of water can replace water and fixate the precursor ions during activation of the catalyst. These methods can yield relatively high loadings of single atoms, up to at least 1 atom per nm2 . In this manner, CheFi applied to carbon support with a surface area of 1200 m2 /g has yielded 30wt% Pt as single isolated atoms. This density is achievable over other carbons, including those with no functional groups (diamond powder) as well as on oxide supports.

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