Understanding the Mechanism of Urea Oxidation from First-Principles Calculations

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Electrocatalysts for urea oxidation reaction (UOR) are crucial for sustainable treatment of urea-enriched wastewater.
• A clear understanding of UOR product formation mechanisms is lacking, hindering catalyst performance improvement.

Purpose of the Study:

• To investigate the thermodynamics of UOR pathways producing N₂, NO₂^-, and NO₃^- on a β-Ni(OH)₂ surface.
• To elucidate the factors controlling selectivity between different UOR products.
• To explore the effect of copper (Cu) doping on UOR selectivity.

Main Methods:

• Density functional theory (DFT) calculations.
• Computational hydrogen electrode (CHE) model.
• Thermodynamic analysis of reaction pathways.

Main Results:

• N₂ formation favors an intramolecular mechanism.
• NO₂^- and NO₃^- are produced in a 1:1 ratio with OCN^-.
• Surface intermediate binding and deprotonation control N₂ vs. NO₂^-/NO₃^- selectivity.
• Cu doping increases N₂ selectivity by raising the limiting potential for NO₂^- formation.

Conclusions:

• The study provides atomic-level insights into UOR mechanisms on NiO_xH_y electrocatalysts.
• Thermodynamic analysis clarifies product selectivity based on surface interactions and deprotonation.
• Cu doping presents a viable strategy for enhancing N₂ selectivity in UOR.