Growth and auto-oxidation of Pd on single-layer AgO_x/Ag(111)

Journal Article · Tue Feb 25 00:00:00 EST 2020 · Physical Chemistry Chemical Physics. PCCP (Print)

DOI:https://doi.org/10.1039/c9cp06973a· OSTI ID:1767696

Mehar, Vikram  ^[1]; O’Connor, Christopher R.  ^[2]; Egle, Tobias  ^[2]; Karatok, Mustafa  ^[2]; Friend, Cynthia M.  ^[2]; Weaver, Jason F.  ^[1]; Madix, Robert J.  ^[2]

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1. Univ. of Florida, Gainesville, FL (United States)
2. Harvard Univ., Cambridge, MA (United States)

Here, we investigated the growth and auto-oxidation of Pd deposited onto a AgO_x single-layer on Ag(111) using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). Palladium initially grows as well-dispersed, single-layer clusters that adopt the same triangular shape and orientation of Ag_n units in the underlying AgO_x layer. Bi-layer clusters preferentially form upon increasing the Pd coverage to ~0.30 ML (monolayer) and continue to develop until aggregating and forming a nearly conformal Pd bi-layer at a coverage near 2 ML. Analysis of the STM images provides quantitative evidence of a transition from single to bi-layer Pd growth on the AgO_x layer, and a continuation of bi-layer growth with increasing Pd coverage from ~0.3 to 2 ML. XPS further demonstrates that the AgO_x layer efficiently transfers oxygen to Pd at 300 K, and that the fraction of Pd that oxidizes is approximately equal to the local oxygen coverage in the AgO_x layer for Pd coverages up to at least ~0.7 ML. Our results show that oxygen in the initial AgO_x layer mediates the growth and structural properties of Pd on the AgO_x/Ag(111) surface, enabling the preparation of model PdAg surfaces with uniformly distributed single or bi-layer Pd clusters. Facile auto-oxidation of Pd by AgO_x further suggests that oxygen transfer from Ag to Pd could play a role in promoting oxidation chemistry of adsorbed molecules on PdAg surfaces.

• Research Organization: Energy Frontier Research Centers (EFRC) (United States). Integrated Mesoscale Architectures for Sustainable Catalysis (IMASC); Harvard Univ., Cambridge, MA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0012573
• OSTI ID: 1767696
• Alternate ID(s): OSTI ID: 1602887; OSTI ID: 1846157
• Journal Information: Physical Chemistry Chemical Physics. PCCP (Print), Vol. 22, Issue 11; ISSN 1463-9076
• Publisher: Royal Society of Chemistry
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
catalysis (heterogeneous)
mesostructured materials
materials and chemistry by design
synthesis (novel materials)