Interaction of CO₂ with MnO_x /Pd(111) Reverse Model Catalytic Interfaces.

Area of Science:

• Surface Science
• Heterogeneous Catalysis
• Materials Chemistry

Background:

• CO₂ activation on metal/metal oxide interfaces is vital for chemical conversion but often rate-limiting.
• Understanding these interfaces is key to designing efficient heterogeneous catalysts.
• Model catalyst systems provide controlled environments to study fundamental surface reactions.

Purpose of the Study:

• Investigate the interaction of CO₂ with MnO_x clusters on a Pd(111) surface.
• Determine the effect of MnO_x nanocluster size on CO₂ activation.
• Identify the role of interfacial sites in CO₂ activation.

Main Methods:

• Utilized temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS).
• Employed ultra-high vacuum (UHV) conditions for surface analysis.
• Prepared model catalysts with varying MnO_x coverages on Pd(111).

Main Results:

• CO₂ activation was enhanced by decreasing MnO_x nanocluster size (lower preparation temperature to 85 K).
• Pristine Pd(111) and thick MnO_x overlayers did not activate CO₂.
• CO₂ activation occurred at sub-monolayer MnO_x coverages (∼0.7 ML), indicating interfacial active sites involving MnO_x and Pd.

Conclusions:

• Small MnO_x nanoclusters on Pd(111) significantly enhance CO₂ activation.
• The interfacial region between MnO_x and Pd(111) is critical for CO₂ activation.
• Tailoring nanocluster size and interface structure is a promising strategy for CO₂ conversion catalysis.