Electrochemical Nitrate Reduction with Low-Index Cu Single Crystals: Selectivity Trends in Alkaline Solution

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrochemical nitrate (NO3-) reduction offers a sustainable route to ammonia (NH3) synthesis.
• Copper (Cu) is a key catalyst, but its surface structure's role in NH3 selectivity remains unclear.

Purpose of the Study:

• To investigate how different copper crystal facets (Cu(100), Cu(110), Cu(111)) influence the selectivity and efficiency of electrochemical nitrate reduction to ammonia in alkaline media.

Main Methods:

• Electrochemical nitrate reduction experiments using Cu(100), Cu(110), and Cu(111) single-crystal electrodes.
• Quantification of product distributions (including NH3) across a range of applied potentials.
• Quantum mechanical calculations to understand reaction mechanisms and intermediate stabilization.

Main Results:

• Cu(100) and Cu(110) surfaces demonstrated comparable rates and selectivity for NH3 production.
• Cu(100) achieved >95% Faradaic efficiency for NH3 over a wide potential range, outperforming Cu(111).
• Nitrite reduction voltammograms effectively predicted electrocatalytic performance for all tested Cu surfaces.

Conclusions:

• Copper surface structure critically dictates selectivity in electrochemical nitrate reduction to ammonia.
• The Cu(100) facet is a highly promising candidate for efficient and selective ammonia synthesis.
• Understanding metal-adsorbate interactions provides guidelines for designing advanced copper-based electrocatalysts.