Au₃-Decorated graphene as a sensing platform for O₂ adsorption and desorption kinetics

Area of Science:

• Surface Science
• Materials Science
• Physical Chemistry

Background:

• Understanding molecular adsorption/desorption kinetics is crucial for fundamental and applied science.
• Quantifying energy barriers on few-atom clusters presents a significant challenge.

Purpose of the Study:

• To present a novel method for quantifying adsorption and desorption energy barriers on few-atom clusters.
• To apply this method to oxygen adsorption on gold (Au3) clusters supported on graphene.

Main Methods:

• Utilizing reaction-induced changes in graphene substrate doping levels to monitor adsorption.
• Employing graphene field-effect transistors with deposited Au3 clusters.
• Using controlled electrical current pulses for thermal desorption.
• Performing density functional theory (DFT) calculations for comparison.

Main Results:

• Estimated adsorption energy barrier for O2 on Au3 to be 0.45 eV.
• Determined oxygen binding energy on Au3/graphene to be 1.03 eV.
• Measured activation entropy of 1.4 meV K⁻¹.
• DFT calculations corroborated experimental findings.

Conclusions:

• The new method effectively quantifies adsorption/desorption kinetics on few-atom clusters.
• The high activation entropy is attributed to hindered motion of the Au3 cluster upon O2 adsorption.
• This work provides valuable insights into molecule-surface interactions at the nanoscale.