Oxygen adsorption on gold nanofacets and model clusters

Area of Science:

• Surface Science
• Materials Science
• Physical Chemistry

Background:

• Understanding gas-surface interactions is crucial for catalysis and materials development.
• Gold surfaces are widely studied for their catalytic properties, yet oxygen interaction remains complex.
• Previous studies have yielded conflicting results on oxygen adsorption on gold.

Purpose of the Study:

• To investigate the interaction of molecular oxygen with gold (Au) crystal surfaces.
• To determine the adsorption behavior and dissociation pathways of oxygen on Au under specific experimental conditions.
• To elucidate the role of electric fields in oxygen-gold interactions.

Main Methods:

• Time-resolved (atom-probe) field desorption mass spectrometry (FDMS) was employed to study oxygen interaction with Au field emitter tips.
• Density Functional Theory (DFT) calculations were performed to model oxygen interaction with Au clusters and surfaces.
• Experimental conditions included pressures below 10(-4) mbar and temperatures between 300-350 K with applied electric fields of 6 V/nm.

Main Results:

• No oxygen adsorption was observed on clean Au facets under the studied conditions.
• Molecular oxygen (O2) primarily underwent ionization at critical distances above the Au surface, rather than dissociation.
• DFT calculations indicated weak oxygen interaction with Au10 clusters and Au(100) surfaces, with no binding on {210} facets.
• Inclusion of electric fields in DFT calculations increased the activation energy for oxygen dissociation.

Conclusions:

• Molecular oxygen does not adsorb or dissociate on clean gold surfaces under the investigated low-pressure, moderate-temperature conditions.
• Applied electric fields inhibit oxygen dissociation, explaining the lack of atomic oxygen detection via FDMS.
• The findings provide insights into the surface chemistry of gold and the influence of electric fields on gas-surface reactions.