| AVS 65th International Symposium & Exhibition | |
| Fundamental Discoveries in Heterogeneous Catalysis Focus Topic | Wednesday Sessions |
| Session HC+SS-WeM |
| Session: | Mechanisms and Reaction Pathways of Heterogeneously Catalyzed Reactions |
| Presenter: | Nassar Doudin, Pacific Northwest National Laboratory |
| Authors: | N. Doudin, Pacific Northwest National Laboratory J. Cheng Liu, Tsinghua University, China M.D. Marcinkowski, Pacific Northwest National Laboratory M.-T. Nguyen, Pacific Northwest National Laboratory J. Li, Tsinghua University, China V.-A. Glezakou, Pacific Northwest National Laboratory G.S. Parkinson, Vienna University of Technology, Austria R. Rousseau, Pacific Northwest National Laboratory Z. Dohnálek, Pacific Northwest National Laboratory |
| Correspondent: | Click to Email |
Single-atom catalysts have recently attracted great attention due to their ultimate metal efficiency and the promise of novel properties. However, at the atomic level, little is known about their stability, interactions with the support, and mechanisms by which they operate. Recently it has been shown that on Fe3O4(001) surface, single metal atoms can be stabilized to temperatures as high as 700 K [1]. This high stability makes Fe3O4(001) a promising support for model studies of single atom catalysts. Here, we present a room-temperature study of H2 dissociation on single Pd atoms on Fe3O4(001) followed by H atom spillover via scanning tunneling microscopy (STM) and density functional theory (DFT). The exposure to H2 at 300 K results in the appearance of bright double protrusions located on surface iron ( FeS) sites. Such protrusions were observed previously [2] following the adsorption of atomic H and hydroxyl formation (OSH) on bare Fe3O4(001). By analogy, we attribute the features observed here to OSH species. The DFT calculations further reveal that H2 dissociates heterolytically and spills over both hydrogen atoms onto Fe3O4(001). When the exposure to H2 is increased, the density of OSH’s is also observed to increase. With approximately every fourth surface oxygen atom hydroxylated, many areas show a local order with OSH’s spaced according to the (√2×√2)R45° surface reconstruction. STM data further indicate that H atoms diffusion is accelerated in the presence of coadsorbed water. At highest coverages of OSH’s (approximately every second oxygen atom hydroxylated), the reconstruction is lifted, and the Pd atoms become destabilized . These studies clearly demonstrate that single Pd atoms can efficiently dissociate H2 that spills over onto a reducible oxide support that can be extensively hydroxylated.
[1] R. Bliem et al. Science 346, 6214 (2014).
[2] G. S. Parkinson et al. Phys. Rev. B 82, 125413 (2010).