Direct Electrochemical Ammonia Synthesis from Nitric Oxide

Area of Science:

• Electrochemistry
• Catalysis
• Environmental Science

Background:

• Nitrogen oxide (NO) removal from exhaust is crucial for environmental protection.
• Electrochemical ammonia synthesis (EAS) from nitrogen (N2) faces challenges with low reaction rates and Faradaic efficiency (FE).

Purpose of the Study:

• To propose and investigate an alternative EAS route utilizing exhaust NO.
• To identify efficient electrocatalysts for NO reduction reaction (NORR) to ammonia (NH3).

Main Methods:

• Density Functional Theory (DFT) calculations to screen catalysts and predict reaction pathways.
• Descriptor-based approach to identify optimal transition metal catalysts.
• Experimental validation using a copper (Cu) foam electrode for electrocatalytic NORR.

Main Results:

• DFT calculations showed NORR is more active than N2 reduction (NRR), with copper (Cu) identified as the most active catalyst.
• Kinetic barrier calculations confirmed NH3 as the preferred product over H2, N2O, and N2 on Cu.
• Experimental results demonstrated a record-high EAS rate of 517.1 μmol cm−2 h−1 and FE of 93.5% at -0.9 V vs. RHE, with stable performance over 100 hours.

Conclusions:

• Electrocatalytic reduction of NO offers a viable alternative to traditional EAS from N2.
• Copper-based catalysts exhibit high activity and selectivity for NO reduction to ammonia.
• This approach simultaneously addresses NO pollution and ammonia production.