Understanding the Selectivity Differences of NO Electroreduction on Ag and Au Electrodes

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Noble metals silver (Ag) and gold (Au) exhibit similar chemical reactivity but distinct catalytic selectivity in nitric oxide (NO) electroreduction.
• Hydroxylamine is a common product on Ag electrodes, but typically not observed on Au electrodes.

Purpose of the Study:

• To elucidate the fundamental reasons behind the differing catalytic selectivity of Ag and Au for NO electroreduction.
• To understand the factors governing hydroxylamine production versus ammonia formation.

Main Methods:

• Utilizing first-principles calculations to investigate reaction mechanisms.
• Employing the electric field controlling constant potential (EFC-CP) method for electrochemical analysis.
• Performing comprehensive electrochemical barrier calculations and kinetic analysis.

Main Results:

• Identified distinct NO adsorption configurations: vertical on Ag and inclined on Au, leading to different intermediate pathways.
• Determined that the adsorption strength of NH2OH* is the primary factor influencing product selectivity.
• Observed that NH2OH* readily desorbs from Ag to form hydroxylamine, whereas it binds strongly to Au, favoring further reduction to ammonia.

Conclusions:

• The difference in NH2OH* adsorption strength on Ag and Au dictates the selectivity of NO electroreduction.
• This research provides critical insights for designing advanced electrocatalysts for targeted hydroxylamine production.