Deciphering Cation-Stabilized *NO₂ at the Molecular Level in Electrocatalytic Nitrate Reduction.

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Electrochemical nitrate reduction (NO3RR) is a sustainable route to ammonia (NH3) production.
• Understanding interfacial reaction dynamics is crucial for NO3RR catalyst design.
• Current NO3RR catalysts lack molecular-level mechanistic insights.

Purpose of the Study:

• To unravel the synergistic interfacial mechanism for rational catalyst design in NO3RR.
• To investigate the role of electrolyte cations in stabilizing key reaction intermediates.
• To develop a generalizable strategy for designing advanced electrocatalysts for NO3RR.

Main Methods:

• In situ Raman spectroscopy
• Multiscale simulations
• Atomic-scale catalyst design using Au single-crystal surfaces
• Heteroatom modification (Sn)

Main Results:

• A cation-mediated stabilization mechanism for the *NO2 intermediate was uncovered.
• Electrolyte cations were shown to modulate electric fields and stabilize *NO2 via interfacial coordination.
• Sn heteroatom modification weakened *NO2 adsorption and enhanced proton transfer, leading to improved NH3 selectivity.
• Synergistic modulation of electronic, ionic, and solvent effects was achieved.

Conclusions:

• Electrolyte cations play a critical role in NO3RR by stabilizing intermediates and controlling reactivity.
• A paradigm shift towards integrated catalyst design considering the entire electrochemical interface is proposed.
• The findings provide molecular-level insights and a strategy for designing efficient electrocatalysts for NO3RR and related reactions.