Tuning reactivity layer-by-layer: formic acid activation on Ag/Pd(111)

Area of Science:

• Materials Science
• Surface Science
• Catalysis

Background:

• Ultrathin metal films offer tunable electronic structures for heterogeneous catalysis.
• Controlling material properties is key to enhancing reactivity and selectivity.
• Formic acid decomposition is vital for hydrogen (H2) generation in fuel cells.

Purpose of the Study:

• To investigate the reactivity of a 1-atomic layer silver (Ag) film on palladium (Pd(111)) towards formic acid.
• To compare the catalytic behavior of ultrathin Ag films with bulk Ag.
• To understand the role of electronic structure modification in catalytic performance.

Main Methods:

• Infrared reflection absorption spectroscopy (IRRAS) for surface analysis.
• X-ray photoelectron spectroscopy (XPS) for electronic structure determination.
• Density functional theory (DFT) calculations to model the system.

Main Results:

• A 1-atomic layer Ag/Pd(111) film shows significant reactivity towards formic acid below room temperature, unlike bulk Ag.
• Two-monolayer Ag films exhibit unreactive behavior, reverting to bulk Ag properties.
• The Ag monolayer is continuous and electronically modified compared to bulk Ag, confirmed by spectroscopy and DFT.

Conclusions:

• The electronic structure of Ag monolayers on Pd(111) is altered, leading to distinct catalytic reactivity.
• Enhanced reactivity is observed only for the first atomic layer, emphasizing the need for precise material engineering.
• This study demonstrates the potential of ultrathin films for tailored catalytic applications.