Nitrate adsorption and reduction on Cu(100) in acidic solution.

Area of Science:

• Electrochemistry
• Surface Science
• Computational Chemistry

Background:

• Nitrate and nitrite are key intermediates in nitrogen cycling and environmental remediation.
• Understanding their adsorption and reduction on metal surfaces is crucial for catalytic applications.

Purpose of the Study:

• To investigate the electrochemical behavior of nitrate adsorption and reduction on a copper (Cu(100)) surface in acidic solution.
• To elucidate the structural transformations of adsorbed nitrate and nitrite intermediates.
• To determine the coordination of these species to the copper surface.

Main Methods:

• Electrochemical methods (cyclic voltammetry, potentiostatic reduction).
• In situ electrochemical scanning tunneling microscopy (EC-STM) for surface imaging.
• Surface-enhanced Raman spectroscopy (SERS) for vibrational analysis.
• Density functional theory (DFT) calculations for electronic structure and bonding.

Main Results:

• Nitrate reduction initiates at -0.3 V vs Ag/AgCl, peaking at -0.58 V.
• Distinct adlattices of nitrate (2x2) and nitrite (c(2x2)) were observed on Cu(100) with potential-dependent interconversion.
• In situ STM revealed dynamic adlayer structures throughout the potential range.
• DFT calculations confirmed twofold coordination of both nitrate and nitrite to the Cu(100) surface.

Conclusions:

• The study provides a detailed mechanistic understanding of nitrate reduction on Cu(100).
• Structural dynamics of nitrate and nitrite adlayers are critical to the reduction process.
• DFT results support the proposed surface coordination and bonding.