Fermi Level Equilibration and Charge Transfer at the Exsolved Metal-Oxide Interface.

Area of Science:

• Materials Science
• Surface Science
• Catalysis

Background:

• Exsolution is a method for creating oxide-supported metal nanocatalysts via redox-driven precipitation.
• Exsolved nanocatalysts feature a stable metal-oxide interface beneficial for catalysis.
• The electronic interactions at this interface are not well understood but impact catalytic activity.

Purpose of the Study:

• To investigate the electronic interactions at the metal-oxide interface in exsolved nanocatalysts.
• To confirm charge transfer between the host oxide and the exsolved metal.
• To elucidate the Fermi level evolution during metal exsolution.

Main Methods:

• Ambient pressure X-ray photoelectron spectroscopy (AP-XPS).
• Theoretical analysis.
• Synthesis of SrTi0.65Fe0.35O3-δ (STF) with exsolved iron (Fe0).

Main Results:

• Demonstrated a two-stage Fermi level (EF) evolution during Fe0 exsolution from STF.
• Observed an initial EF rise due to electron doping from oxygen vacancies.
• Showed EF stabilization upon Fe0 precipitation, indicating charge transfer and equilibration between STF and Fe0.

Conclusions:

• Confirmed charge transfer between the host oxide (STF) and exsolved Fe0.
• Highlighted the significance of electronic metal-support interactions for exsolved nanocatalyst optimization.
• Emphasized the need to consider these interactions for improved catalytic performance.