Heterogeneous mercury oxidation on au(111) from first principles

Area of Science:

• Computational chemistry
• Surface science
• Catalysis

Background:

• Mercury oxidation on catalytic surfaces is crucial for environmental remediation.
• Understanding reaction mechanisms on gold surfaces requires detailed theoretical investigation.

Purpose of the Study:

• To elucidate mercury oxidation mechanisms on Au(111) using DFT.
• To identify rate-limiting steps and the influence of hydrogen on oxidation pathways.

Main Methods:

• Density Functional Theory (DFT) with Perdew and Wang approximation (PW91).
• Langmuir-Hinshelwood mechanism analysis.
• Climbing Image-Nudged Elastic Band (CI-NEB) for activation energy calculations.

Main Results:

• The second chlorine attachment step (HgCl to HgCl2) is the rate-limiting endothermic step.
• Mercury oxidation prefers a stepwise pathway (Hg → HgCl → HgCl2).
• Adsorbed hydrogen atoms significantly lower activation energies for mercury oxidation.

Conclusions:

• The stepwise oxidation of mercury on Au(111) is energetically favored.
• Hydrogen plays a catalytic role by facilitating chlorine detachment from the gold surface.
• DFT provides critical insights into the electronic properties governing mercury oxidation on gold.