PNNL

Abstract

Single atom catalysis has been a topic of increasing interest due to the potential for improved selectivity, reactivity, and catalyst cost. However, single atom catalysts are still difficult to characterize under realistic reaction conditions, leading to controversy regarding the capabilities of single atoms and a need for model studies. Herein, we examine the reaction of methanol on single Pd atoms supported on Fe3O4(001) under ultra-high vacuum conditions. On clean Fe3O4(001) a small fraction of methanol is converted to formaldehyde through a methoxy intermediate at 516 K. The addition of single Pd atoms lowers the barrier to C-H bond cleavage by a factor of two, resulting in formaldehyde desorption by 290 K. However, Pd atoms sinter by 300 K in the presence of methanol, and Pd clusters do not exhibit the same chemistry. Single atom sites significantly lower the barrier to the oxidation of methanol, although their stability remains an issue.